2. SIKOSTART 3RW24 Principle of Operation 2.1 Starting & Stopping Continuous Operation Protection and Control... 2.

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2 CONTENTS Page No. 1. Introduction 1.1 Motor Transmission System Conventional Starting Methods Why use 3RW24 Controllers Features of 3RW RW24 Principle of Operation 2.1 Starting & Stopping Continuous Operation Protection and Control Typical applications Motor feeder circuit 4.1 Motor Feeder Protection Parallel Starting of Motors Installation in parallel with a frequency converter Operation with Capacitor Bank Typical Circuit Diagrams Product Range, Technical Data Dimension Drawing Installation & Commissioning 8.1 Installation Tips Commissioning Tips Troubleshooting Maintenance, spare parts, accessories A Appendix Engineering, starter selection... A1.1 - A1.6

3 Introduction 1. Introduction Motor Transmission System The three phase asynchronous motor has been the workhorse of the industry for a long time due to a) its robust and simple construction, and b) its low need for maintenance. Three-phase asynchronous motor The three-phase asynchronous motor features a three-phase winding in the stator which produces a rotating magnetic field owing to its relative physical position with respect to one another and the relative phase displacement of the current flowing through them. The rotation speed is n Sy = 60 x f 1 /p (n Sy = synchronous speed in min 1 ; f 1 = mains frequency in Hz; p = number of pole pairs). This rotational field induces currents in the windings of the rotor which produce a torque which inturn accelerates the rotor in the direction of the rotational field. The asynchronous motor cannot, however, reach the synchronous speed, as also during no-load operation it needs a slight torque to overcome its own frictional losses. At synchronous speed, the induced voltage and thus the rotor current and torque would become zero. It therefore does not run at synchronous speed, i.e. exactly in phase with the stator field, but always asynchronously. The characteristic points on the torque/speed curve are the locked rotor (or initial) torque M A, the pull-up torque M S, the breakdown torque M K and the rated torque M N (*Fig 1.1). To ensure that a motor can run up to rated speed at all, the motor torque M M must be greater than the load torque M L for the entire starting time, as otherwise, motor will be stalled. The difference between M M and M L is the accelerating torque M B, and it must therefore always be greater than zero. This must be taken into account particularly in case of a pronounced pull-up torque (or saddle point), as this is the smallest torque which occurs during running up until rated speed is reached. For each asynchronous motor, the actual shape of the torque/speed characteristic is determined by the constructional particulars of the rotor. M A M S M K M M M L M B M N n K n N n sy n S Locked rotor torque Pull-up torque Breakdown torque Motor torque Load torque Accelerating torque Rated torque Rotational speed at breakdown torque Rated speed Synchronous speed Rotational speed at pull-up torque Fig. 1.1 Typical torque/speed characteristics of a squirrelcage motor and a load 1.1

4 Introduction In the case of a slipring motor the rotor slots contain three-phase windings. One end of each winding is connected internally while the other ends are brought out to the terminal block via sliprings and carbon brushes. The controlled starting of the motor is achieved by the successive bridging out of resistors in the rotor circuit (*Fig. 1.2). Owing to their complicated construction and the resistors,slipring motors are more expensive and require more maintenance work than squirrelcage motors. Therefore, they are used mainly in applications in which a relatively high initial torque is required, but in which the starting current may not exceed the rated current to any great extent (e.g. mills and hoists). If a slipring motor is to be operated using a soft start controller e.g., it needs a fixed resistance in the rotor circuit (here e.g. R LV2 ) to ensure that the motor has sufficient accelerating torque M B to run up. This resistance can be bridged once the motor has come up to speed. In the case of a squirrel-cage motor, rotor windings are not accessible. The rotor slots contain bars of copper, bronze or aluminium and the ends are connected on both sides via shorting rings. Aluminium rotor bars are cast directly into the rotor slots. Common forms of squirrel-cage rotor are the wedge cage bar, the high cage bar and the double cage bar (*Fig. 1.3) The characteristic values of a motor such as locked rotor torque, pull-up torque and breakdown torque as well as the initial starting current and rated current can be found in the relevant catalogues (the M11 catalogue for Siemens motors). If needed, the torque/speed characteristic can be determined from this with sufficient accuracy. In the torque/speed characteristic as shown in (Fig. 1.3) it can be seen, for example, that the breakdown torque for motors with a high resistance in the rotor circuit is located at speeds close to zero and that the curve has no saddle. This type of motor is therefore used when a high initial torque is required. In case of squirrel-cage motors with a predeterminded slot form, the torque/speed characteristic can only be influenced via the frequency of the value of the terminal voltage. Fig. 1.2 Torque/speed characteristic of a slipring motor with various rotor resistances Fig. 1.3 Torque/speed characteristic of cage motors with various rotor types 1.2

5 Introduction 1 Transmission system When using a gearbox between the motor and the load, the moment of inertia of the load must be referred to the motor speed to determine the effective moment of inertia at the motor shaft: J L (M) = J L x (n L /n M ) 2 The same principle applies to the torque. The load torque characteristic must be converted proportionally to the transmission ratio and the efficiency of the transmission system: M L (M) = M L x (n L /n M ) x 1/h M L M L (M) n M n L h J L J L (M) Load torque Load torque referred to the motor shaft Motor speed Load speed Efficiency of the transmission system Moment of inertia of the load Moment of inertia of the load referred to the motor shaft Characteristic data of some transmission systems Type of transmission Transmission ratio Transmission efficiency h n M n L Spur gear system upto 8 single-stage to 45 two-stage to 250 three-stage Worm gear upto 8 single-stage single gear double gear Belt drive upto Chain drive upto Friction gear system upto Note In some lists, machine manufacturers specify the flywheel moment (or rotative moment) GD 2 instead of the moment of inertia J. Its numerical value, assuming it was specified in kgm 2, should be converted using the following formula. [J] = [GD 2 ] (J in kgm 2 ) 4 1.3

6 Introduction 1.2 Conventional starting methods The most prevalent way of providing electrical energy to the motor has been through starters, which consisted of one or a combination of electromechanical switching devices called contactors. Direct-on-line starting This is the most common and simple way of controlling energy flow to an induction motor. Full line voltage is applied on the stator terminals while the rotor is stationary. The low impedance, characteristic of the stator when the motor is both stationary and accelerating, results in high line current. The typical starting current for Direct-online starting is in the range of 6-7 times the full load current. The starting current is independent of the motor load - the current increases with the acceleration of the motor finally falling to the rated current when the motor reaches its full speed. As the torque generated is proportional to the current, such starting is also associated with high starting torque. Although direct-on-line is the simplest and most economical method of starting, the apparent advantages get offset by high cost penalties in terms of increased maintenance, reduced life of the transmission system and higher risk of motor failure. Direct-on-line starting sometimes become unviable when loads are operated in DG sets, because of frequent tripping of the DG during high current surges associated with DOL starting. Star-delta starting Star delta starting is the simplest form of reduced voltage starting. The motor is started in star configuration, and then after a preset time is switched over to delta configuration. Starting in star reduces the voltage applied to the motor terminals and when the motor accelerates to 80% rated speed the changeover is made to Delta configuration. If the motor has not accelerated sufficiently before switching to delta, a very high current will flow as in DOL starting. During starting in star mode; the generated torque is one third of the rated torque. If a drive requires 40% rated torque to break away then one has to revert to other means of starting rather that stardelta starting. Fig. 1.4 Starting characteristics for direct-on-line starting in the delta configuration Fig. 1.5 Starting characteristic in the case of star-delta starting 1.4

7 Introduction 1 Auto-transformers and stator-resistance starters Auto-transformer and stator-resistance starters allow starting torque and currents to be reduced by decreasing the initial terminal voltage. The resistances are cut in steps as the motor reaches full speed. Frequently the resitances are movable blades immersed in an electrolytic liquid. Such starters are usually bulky and expensive, both in terms of cost and maintenance. The starting procedure may comprise more than one stage which naturally involves extensive control circuit and switchgear. Furthermore the starting resistors dissipate a huge amount of heat during starting. In the following table the value ranges of locked rotor torque and initial current for the conventional starting methods are summarized: Fig. 1.6 Schematic diagrams of the auto-transformer and stator-resistance starting methods Direct-on-line Star-delta Resistance Auto- starting starting starting transformer starting starting Locked rotor M N M N M N M N M N M N torque Initial current I N I N I N I N Adjustable Required no. 3 min. of /6* of motor terminals * Delta connection Summary: l A common characteristic of all the conventional starters is that they do not allow fine adjustment of motor parameters (current, torque) to match the specific problems during starting. l The specific requirements like smooth increase in supply voltage, gradual increase in torque values in tune with the motor acceleration, smooth stopping of the motor on removal of supply or current limit during starting can only be met with the help of electronic motor controllers like 3RW

8 Introduction 1.3 Why use 3RW24 Controller? Too often the starter/motor combination is the least considered component of the entire installation and for too long the occurrence of motor burnouts, damaged drive systems and resultant production downtime has been tolerated as an inevitable maintenance cost. But things have changed with the introduction of electronic motor controllers such as the 3RW24. Electronic motor controllers 3RW24 control the voltage applied to asynchronous motors during start up, reducing the starting current and torque to provide a smooth, stepless acceleration. The derived benefits from such starting are the following:- A. The Motor Chemical and Process Industry Application: Fluid pumping Problem: Frequent start/stop of the motors using conventional methods of starting cause damage to the motor shaft. Solution: Due to the reduction of starting torque and also the starting current, the electrical and mechanical stresses on the motor are reduced to a great extent. This has a great bearing in the longevity of the motor. Start/Stop by use of electronic motor controller 3RW24 eliminates damage of the motor shaft. B. The Drive Gear Steel Plants Application: Cold Rolling Mills Problem: High torque transients during starting cause high stress on the chain gear. Solution: Smooth increase in operating voltage during start up eliminates transient torque associated with conventional starting methods thereby increasing the life of driving gears such as belts, chains, couplings, gears etc. Use of electronic motor controller 3RW24 reduces starting torque thereby increasing chain life. C. The Load Textile Industry Application: Ring frame machines Problem: Due to start with sudden jerks the threads tend to break. Solution: Loads are protected from current and torque surges during start up operations. Jerk starts in conveyors are eliminated, water hammer effects in pumps are reduced and wear and tear in textile machines is reduced due to smooth start. Use of electronic motor controller 3RW24 ensures smooth acceleration thereby preventing such breakdowns. D. The Supply Voltage Mines and Quarries Application: Crusher & Excavatrors Problem: If working on a DG set, the starting current has to be limited to prevent frequent tripping of the DG set. Solution: The supply voltage regulation is improved by reduction of starting currents and avoidance of transient current surges during start up. The minimum torque required determines the starting current and stepless control of voltage avoids current surges. Electronic motor controller 3RW24 reduces starting currents and transients thereby preventing frequent tripping. E. Energy Saving Software, Healthcare, Pharmaceutical Industry Application: Refrigeration compressors. Problem: The compressor has an ON - Off duty cycle. But as the motors are hardly turned off during NO load periods there are huge energy losses. Solution: Operation of the equipment On Demand rather than ON load - OFF load continuous running can lead to more efficient energy planning and savings in Energy Bills. Frequent start/stop by conventional methods decrease the lifetime of the electromechanical devices. Electronic motor controllers 3RW24 enable frequent starting and stopping of the motor because of reduced electrical and mechanical losses. Moreover due to reduction of voltage during no load periods there is some energy savings. 1.6

9 Introduction 1 F. Process Safety Municipal Corporations, Waterworks etc. Application: Sewage, water pumping Problem: Damages are caused in pipe work due to water hammer effects. Many application requires smooth stopping of the motor, like conveyors in bottling plants, centrifugal pumps to avoid water hammer effects etc. Solution: Smooth stop by Electronic motor controller 3RW24 reduces water hammer effect and ensures long life of the pipelines. For all the above reasons electronic motor controllers 3RW24 are increasingly being used in industry and the trade. Electronic motor controllers 3RW24 provide complete protection for all drives by restricting the motor torque and starting current. The benefits of using an electronic motor controller 3RW24 can be summarized as follows: 1. Mechanical Reduced cost of transmission components - low starting torque. - starting torque adjustable to requirement. Reduced maintenance costs - low starting torque reduces belt slip. Lower repair costs - fatigue effects reduced (star/delta, transformer and single phase starting cause high current peaks). 1.4 Features of 3RW24 a) Standard Features 1. Soft Start l Adjustable torque (0-100%) l Adjustable ramp time (6-50 sec) 2. Soft stop l Adjustable ramp time (6-50 sec). b) Optional features (with I Option) 1. Impulse start with switch on pulse to overcome breakaway friction (starting inertia). 2. Starting with current limit ( % I e ). 3. Energy saving by improving the power factor cosf, during no load periods. This feature is particularly important for drives having long idling periods or running for a long period below 10% normal load. 4. Monitoring of input power with overload trip (stall protection). A relay contact opens when a set limit is exceeded. This can be used as a stall or overload protection of the motor. 5. Overload trip, fixed adjustment between 20 to 200% I e. 6. Feed forward current control to damp possible drive oscillations (e.g. water hammer effects with pumps). 2. Electrical Low starting current - compared to other conventional modes of starting. Low maintenance costs - lower rating contactors with zero current switching. Machine protection - electronic overload trip included with I-Option feature. 1.7

10 Introduction Circuit Designs The electronic motor controller 3RW24 can be operated in two types of circuits. Standard Connection With this circuit, the switching devices for disconnecting and protecting the motor are simply installed in series with the soft starter, the motor is connected to the soft starter with 3 conductors. Delta connection In this case the wiring is similar to star/delta starters. The phases of the soft starter are connected in series with the separate motor windings. The advantage in this connection is that the soft starter has to only carry the phase current, approximately 57% of the motor current I n (conductor current). The conductor current and the phase current are related by the factor For the same kw rating of a motor by using a delta connected soft starter one can opt for lower frame sizes. Choice of connections The standard circuit requires the least wiring outlay. The wiring outlay for the delta connected soft starter is double as that of the standard connection. But when upgradations are made to softstarter from star-delta starters delta connected softstarters prove to be an economical choice. Whatever circuit is chosen, the ability to change modes between the standard circuit and the delta connected circuit, will always provide a real alternative to the conventional mechanical and electromechancial starters. Typical Application Areas l Machines with gearbox, belt or chain drives. l l l l l l l l l l Drives using pole change motors. Conveyor belts (also high speed and high load belts). Machines with high moments of inertia e.g. mills, centrifuges, compactors. Grinding machines, circular saws. Fans and compressors. Pumps, in particular, to reduce water hammer effect with I Option card (damping circuit). Reverse flow heat exchangers. Mixers, extruders, stone crushers. Hoists, escalators Machine tools, textile machines, wiredrawing machines, injection molding machines etc. L1 L2 L3 N Rated current I e of starter corresponds to nominal motor current I n 3 conductors to the motor Fig. 1.7 Standard Connection Rated current I e of starter corresponds to 57% of nominal motor current I n 6 conductors (as in star-delta starters) to the motor. Wiring effort approx. 60% of that of the standard circuit. Fig. 1.8 Delta Connection 1.8

11 3RW24 - Principle of operation 2. 3RW24 Principle of operation 2.1 Starting and stopping 2 The 3RW24 electronic motor controllers are designed for soft start and soft stop of three phase asynchronous motors and employ a fully controlled three phase thyristor circuitry. Each of the phases L1, L2 and L3 has two thyristors in anti parallel configuration. Soft starting By controlling the switch-on-point of the thyristors relative to voltage zero crossing in each half wave of the alternating current cycle the energy flowing to the motor is controlled. For the purpose of soft starting the voltage is continuously ramped up from a base voltage, by controlling the firing angle of the thyristors. The rate of firing angle of the thyristors (ramp time) is also adjustable. The base voltage is set to supply sufficient torque to achieve breakaway and the ramp rate is adjusted according to the inertia of the load. The actual voltage applied to the motor during starting is a function of both load (motor) impedance and the thyristor firing angle. Once the motor reaches its rated speed the thyristors are turned FULL ON. Free coasting to stop, direct switching off of the mains voltage If the supply voltage is switched off directly, the motor coasts down to stop over a period determined by the moment of inertia of the drive and the frictional losses. Higher the moment of inertia longer is the time taken to stop. Both the situations may be undesirable either for reasons of safety with regard to material fatigue or because of unwanted abrupt stopping of the load. The torque and current curves for different voltages (in each case constant values of the terminal voltage) referred to the rated voltage, are represented by dotted lines in Figure 2.1. The bold curves correspond to a start during which the terminal voltage is increased as function of time. Fig. 2.1 Torque and starting current characteristics during starting with a voltage ramp Fig. 2.2 Soft starting with voltage ramp 2.1

12 3RW24 - Principle of operation Soft stop With soft stop operation the voltage applied to the motor is reduced to zero as a ramp function (adjustable). This is typically the case of conveyor belts, escalators or hoists, to ensure that the material being conveyed does not fall over causing accidental hazards. The main contactor is opened with zero current on completion of ramp down. If zero current switching without soft stop is required, the deceleration ramp should be set to the minimum time. This increases the life of the main switching contactor. It may be noted that soft stopping is not the same as Braking. Braking is achieved, with electronic brakes, by means of injecting DC current in any of the two phases. If a new ON command is given during soft stopping, the stopping operation is immediately interrupted and the motor is re-started. Fig. 2.3 Speed curve for the various types of stop Fig. 2.4 Behaviour of the terminal voltage during switch-off with the soft stop function Caution!!! The drive and the feeder (Motor, overload relay, contactor etc.) must be selected for the higher current drawn during the stopping operation. Pump stop Owing to the very small moment of inertia of centrifugal pumps and the counter pressure of the liquid in the piping system, the pump drive can come to an abrupt standstill upon switch-off. This can cause severe pressure shock waves, known as Water hammer, in the piping system which can produce loud noises and can lead to mechanical problem of non-return valves and flaps. The problems described above can be avoided if the voltage at the motor terminals is not interrupted suddenly (free coasting) after the OFF command, but is lowered over a period of time in such a way that the actual delivery of the pump is reduced gradually to zero. For that, the torque characteristics of the motor and pump during run down must be taken into consideration. The Pump stop function of 3RW24 recognizes changes in the torque characteristics of the drive during run-down and actively controls the motor terminal voltage in such a way that an optimal soft stop is achieved. The duration of the pump stop can be adjusted from 6 s to a maximum of 50 s by means of potentiometer (STOP TIME). If a new ON command is given during the pump stop, the stopping operation is immediately broken off and the motor is re-started. Fig. 2.5 Behaviour of the terminal voltage during switch-off with the pump stop function. Caution!!! The drive may already come to a standstill before the stopping time has elapsed which means that a non-zero voltage may still exist across the motor terminals for a few seconds. The drive and the feeder (motor, overload relay, conductor, etc.) must be selected for the higher current drawn during the stopping operation. Note on Water Hammer Like any other moving fluid, flowing water has momentum. When subjected to a sudden change in flow, the energy associated with the flowing water is suddenly transformed into pressure at that location. The force with which this pressure strikes the walls of the pipe can be compared to hammer blow. This occurrence is referred to as water hammer. Flow changes can occur due to operation of valves, starting and stopping of pumps or directional changes caused by pipefittings. The intensity of water hammer effect will depend on the rate of change in the velocity or momentum. Another reason for water hammer is cavitation. This is caused by steam bubble forming or being pushed into a pipe completely filled with water. As the trapped bubble losses its latent heat, the bubble implodes, the wall of water comes back together and the force created can be severe. 2.2

13 3RW24 - Principle of operation 2.2 Continuous operation Full ON In electronic motor controller 3RW24 the voltage applied to the motor terminals is gradually ramped up from a base voltage to full mains voltage. After the motor attains full speed the thyristors are fully turned ON. The power unit for 3RW24 is rated for 150% of the rated current I e. During Full ON condition the 3RW24 monitors the following parameters: l All phases present and are symmetrical l Heat sink temperature l Control voltage l Connection for thermistor motor protection Operation with a bypass contactor The use of a bypass contactor is recommended to reduce losses during continuous operation. On the one hand the power loss in the thyristors is reduced, and on the other hand the power unit can be used to better advantage since it can cool down more quickly (even to the ambient air temperature) before a new start. The bypass contactor can be energized via the internal motor running relay in 3RW24 (Typical circuit diagrams). Within 2 s after the end of the run-up sequence, the contacts of the bypass contactor must have closed, otherwise the 3RW24 is in FULL ON mode. In contrast to the main contactor which is selected in accordance with utilization category AC-3, the bypass contactor need only to be selected for AC-1 switching duty. This is because, it only needs to conduct the operational current of motor and does not have to switch the starting current. Even in the bypass contactor configuration, all the stopping modes (free coasting, soft stop, pump stop) are permitted. With the controlled stopping modes (soft stop, pump stop) the bypass contactor is swichted off via the internal motor running relay before the takes over the current for the stop. Fig. 2.6 Circuit with bypass contactor 2 3 ~ V/ V 3 ~ V/ V L1 L2 L3 L1 L2 L3 CONTROL CIRCUIT RAMP FUNCTION GENERATOR TRIGGER SET 2 ~ V ±5% 2 ~ V ±5% L1 L2 L3 L1 L2 L3 Control inputs Command "Ramp-up" BH Command "Enable" BF Phase current SW P12 N12 ~ ~ = = M H B A INTERNAL SET VALUES Control outputs Signal "In Operation" ME Signal "End of Ramp" MH Signal "Overload" MU EP UM PM PN T1 T2 T3 T1 T2 T3 Block diagram I-OPTION M SEPARATE CONTROL MODULE WITH 3~ LINE & DELTA CONNECTED STARTERS Line Connection Delta Connection W1 V1 U1 M 3~ W2 V2 U2 Fig. 2.7 Schematic for 3RW24 2.3

14 3RW24 - Principle of operation 2.3 Protection and control I-Option card: The use of the I-Option card is recommended at powers above 45 kw and with pump drives. Electronic device protection is provided with a built-in thermistor, which trips the in the event of overtemperature. Short circuit protection of wiring: Conventional short circuit protection of the connections to the controller and to the motor in accordance with the wiring regulations must be provided for. Circuit breakers or additional fuses can be used. Semiconductor fuses: It is recommended to use semiconductor fuses (as per the selection table) for protection of the thyristors against transient short circuit surges. Semiconductor fuses being fast acting prevent the thyristors against such hazards. Thermal protection for motor: is designed for continuous operation with motors up to the rated power. Overload protection to motor should be separately provided. Suitable protection is a thermal overload relay, micro processor based motor protection relay 3RB12, a motor starter, thermistor motor protection or a combination of above can be provided depending on the criticality of load. Single step overload protection Monitoring of the input power. A relay contact opens when a set limit is exceeded. This can be used as a stall or overload protection for the motor. The measured power is also available as an analog signal. Caution!!! The heatsink may reach high temperatures. Depending on the type of device, the maximum heatsink temperature during continuous operation may be as high as 85 O C. 2.4

15 Typical applications 3. Typical applications 3.1 Pumps Load characteristic: M ~ n 2 The load torque increases with the square of the rotational speed (*Figures 3.1 to 3.3) 3 Examples: Centrifugal pumps, submersible pumps, vacuum and high-pressure pumps feeding into open pipe networks (in the case of a closed valve the final torque value is approx. 50% of the value applicable for a fully opened valve). Problem: Particularly in the case of pumps, the pressure wave ( water hammer ) resulting from sudden acceleration and deceleration of the water column must be prevented. This phenomenon can damage not only the pump itself, but also the piping and the check-valves (nonreturn valves) in the piping system. Furthermore, it can cause a loud bang which may disturb those who live near the pump station. Solution with 3RW24: The 3RW24 can effectively prevent the pressure-wave by the functions soft start and pump stop. In this way, the intervals between maintenance can be prolonged and downtime due to excessive mechanical stress becomes a thing of the past. As pumps normally only have a low moment of inertia, selection of the correctly sized controller can usually be carried out directly from the catalogue. Only as an exception (e.g. if the moment of inertia of the total drive is greater than 10 times the moment of inertia of the motor alone) please refer back to Siemens. Selection of the correct setting: The starting voltage should not be too high (Fig. 3.2) as otherwise the water hammer may not be prevented. It should also not be too low (Fig. 3.3), otherwise the motor may not start swiftly. For the entire period of acceleration up to rated speed, the motor torque should be higher than the load torque by approximately 15% of the torque it would produce at full rated terminal voltage (Fig. 3.1) Fig. 3.1 Correct setting of the starting parameters Fig. 3.2 Incorrect setting of the starting parameters * accelerating torque too high Fig. 3.3 Incorrect setting of the starting parameters * starting voltage too low and accelerating torque too small 3.1

16 Typical applications 3.2 Fans Load characteristic: M ~ n 2 The load torque increases with the square of the rotational speed (*Figures 3.4 to 3.6). Examples: Fans, blowers feeding into open ducting networks (in the case of a closed damper, the final torque value is approx. 50% of the value applicable for a fully opened valve), machines with centrifugal action, propeller drives on ships, stirrers, centrifuges, drives causing motion in a straight line against air resistance. Problem: Fans usually have a very large moment of inertia (from 10-times to 200-times the moment of inertia of the motor itself is possible). In the case of direct-on-line starting, such a high moment of inertia will require the full starting current to flow for a long period of time which can cause an undesirable drop in the network voltage. In the case of star-delta starting, there usually is an undesirable current and torque impulse at the instant of the switch-over from the star to the delta configuration. If the motor characteristics happen to be unfavourable, this can almost be equal to a direct-on-line start. Solution with 3RW24: The functions soft start and current limiting prevent high starting currents. Selection of the correct setting: The starting voltage should not be too high (Fig. 3.5), otherwise the corresponding initial starting current may still reach an unacceptable high value before the current limit function takes effect. Also, if the current limiting function is not being used, the ramp time should not be too short (Fig. 3.6) as otherwise the full network voltage will be connected to the motor terminals too early during run-up, and thus the full starting current may still flow. For the entire period of acceleration upto rated speed, the motor torque should be higher than the load torque by approximately 15% of the torque it produces at full rated terminal voltage (Fig. 3.4). Fig. 3.4 Correct setting of the starting parameters Fig. 3.5 Incorrect setting of the starting parameters * starting voltage too high Fig. 3.6 Incorrect setting of the starting parameters * ramp time too short 3.2

17 Typical applications 3.3 Mills Load characteristic: M ~ 1/n The load torque decreases with increasing rotational speed (*Figures 3.7 to 3.9). 3 Examples: Ball mills, lathes, turning and milling machines, winders and peeling machines. Problem: For the initial start, mills need a high breakaway torque. There-after, the required torque to maintain rotation and to accelerate the drive decreases with increasing rotational speed. Therefore, the drive must be provided with sufficient energy to start the mill turning, but thereafter, during running up to speed, the current drawn should not be higher than absolutely necessary. This means that star-delta starting is usually not possible as only 1/3 of the motor torque is available in the star configuration and the motor would only run up after switching over to the delta stage. This would, in effect, be equal to a direct-on-line start. Solution with 3RW24: By means of the impulse start function (or kickstart ), for which the level of switch on pulse can be set between 0 to 200% of rated current, the drive motor is provided with just enough torque for the mill to start turning. Afterwards the torque is dropped as to match the motor torque to the load torque characteristic. Selection of the correct setting: The starting impulse should not be too high (Fig. 3.8) as this would be equivalent to a direct-online start and thus the full starting current would flow and the maximum accelerating torque would be applied to the load. The starting torque impulse should be only a little greater than the breakaway torque of the mill, and the motor torque should be reduced again as quickly as possible after the shaft starts turning (Fig. 3.7). Fig. 3.7 Correct setting of the starting parameters Fig. 3.8 Incorrect setting of the starting parameters * starting switch on pulse setting too high Fig. 3.9 Incorrect setting of the starting parameters * starting switch on pulse setting too high. 3.3

18 Typical applications 3.4 Conveyor belts, elevators, escalators Load characteristic: M = const. The load torque is constant over the entire range of the rotational speed (Figures 3.10 to 3.12). An initial breakaway torque impulse may be required. Examples: Hoists, piston pumps and compressors acting against constant pressure, enclosed blowers, rolling mills, conveyor belts, mills without fan action, machine tools with constant cutting force, escalators. Problem: In the case of direct-on-line starting and stopping persons or objects being conveyed could fall over and be injured or damaged, respectively. In the case of a soft starter with a non-adjustable impulse start function, the start could be equivalent to a direct-on-line start. If the initial start voltage is too low, the motor is blocked by the load torque for too long before the voltage is ramped up high enough (M ~ U 2 ) and the motor torque becomes larger than the load torque. In the case of a star-delta starter, the drive would only run up after the switch-over to the delta configuration, which would be equivalent to a direct-on-line start. Solution with 3RW24: The functions soft start, soft stop and, if required, the impulse start function which is adjustable, ensure that the is ideally suited for the soft starting and stopping of conveyor belts, elevators and escalators. Fig Correct setting of the starting parameters Fig 3.11 Incorrect setting of the starting parameters * starting voltage too high Selection of the correct setting: The starting impulse setting should not be too high (Fig. 3.11) as this would be equivalent to a directon-line start and thus the full starting current would flow and the maximum accelerating torque would be applied to the load. The starting voltage should not be set too low (Fig. 3.12) to ensure that the motor starts to run up at the moment the start signal is given. Fig Incorrect setting of the starting parameters * initial starting voltage too low 3.4

19 Typical applications 3.5 Calenders Load characteristic: M ~ n The load torque increases linearly with the rotational speed (*Figures 3.13 to 3.15). 3 Examples: Calenders, screw conveyors (starting with screw chambers that are not filled), machines for smoothing textiles and paper, mangles. Problem: Calenders typically comprise two rollers positioned one above the other. These turn in opposite directions and press paper or fabric between their contact surfaces. Even in the case of direct-on-line starting, the large moment of inertia of the rollers causes long run-up times during which the full starting current would flow. Also, owing to the high accelerating torque during direct-on-line starting, there may be a danger of tearing the paper of fabric during run-up. This would cause a production standstill and down-time. Fig Correct setting of the starting parameters Solution with 3RW24: By means of the functions soft start and soft stop, 3RW24 effectively avoids the high accelerating torques and limits the starting current. Selection of the correct setting: The start voltage should not be too high (Fig. 3.14) to ensure that the starting current and the accelerating torque are low. The ramp time should not be too long as otherwise the motor may stall at low rotational speed (Fig. 3.15). If this happens, the internal temperature in the starter will rise sharply causing the solidstate device protection of the to operate. For the entire period of acceleration up to rated speed, the motor torque should be higher than the load torque by approximately 15% of the torque it would produce at full rated terminal voltage (Fig. 3.13). Fig Incorrect setting of the starting parameters * initial starting voltage too high Fig Incorrect setting of the starting parameters * ramp time too long 3.5

20 Motor feeder circuit 4 Motor feeder circuit The compact unit 3RW24 is incorporated within a normal motor feeder circuit between the main switchgear and motor (*Fig. 4.1) In principle, the rest of the motor feeder remains unchanged and is designed in terms of the motor power rating. In spite of the considerable decrease in starting current which may be achieved through the use of the, all the elements of the main circuit should be dimensioned for direct-on-line starting and in accordance with the prospective shortcircuit conditions. Depending on the ramp time, the limited starting currents, which are always still greater than the motor rated current, may flow for a relatively longer period of time. This should be borne in mind particularly when selecting the overload protection of the motor. This also applies for the stopping mode, soft stop and pump stop which, unlike the case when the motor coasts to a stop, cause an additional current to flow during run-down. For the short-circuit protection of the power thyristors in the, super-fast acting semiconductor fuses are recommended (*page 4.4 & 4.5). Table 4.1 provide suggestions for the dimensioning of the motor feeder for normal starting conditions (moment of inertia of the total drive J Tot < 10 x J motor ; and motor with rotor class KL10, which means that starting against a load torque of up to 100% the motor rated torque is possible even at an undervoltage of 5%). Fig. 4.1 Principle configuration of a typical motor feeder 4.1

21 Motor feeder circuit 4.1 Motor feeder protection The optimum motor feeder protection can be provided by an overload relay, general purpose HRC fuses and semiconductor fuses. This can be seen clearly from the diagram below, in which the short-circuit and overload protection curves for a 37 kw motor feeder are illustrated. The overload relay is responsible for protecting the motor against overload, the HRC fuses for protecting the switching elements and conductors against overload and short-circuit and the semiconductor fuses for protecting the thyristors against short-circuit. Naturally, the HRC fuses and the overload relay may be substituted by a circuit-breaker. In other words, each and every protection element has its particular purpose. Semiconductor fuses should always be used for thyristors as they provide fast and safe protection for the sensitive semi-conductors at high shortcircuit currents. Moreover, in case of a short-circuit, a fuse can be replaced faster than a string of thyristors which saves long downtimes. 4 Fig. 4.2 Characteristics of the protection elements in a motor feeder incorporating a 4.2

22 Motor feeder circuit 4.2 Parallel starting of motors The power rating of a must be at least as great as the sum of all the motor power ratings. Proper derating should be done if the application demands. The loads should have similar characteristic torque/ speed curves and similar moment of inertia. Fig. 4.4 : Operation in parallel installation with a frequency converter 4.4 Operation of a motor with a power factor correction capacitor Fig. 4.3 Parallel starting of several motors with one 4.3 Installation in parallel with a frequency converter If the motor has to be connected to a motor controller in parallel with a frequency converter, then the load side of the must be disconnected from the motor (Contactor K3) when the converter is in use to protect the RC protection circuits of the thyristors from being damaged through high frequency voltage produced by the converter (Fig. 4.3). Whether a contactor on the load side of the converter (K4) is also necessary must be checked by the user for each individual case. F1 Line fuses for F2 Line fuses for frequency converter F2.1 Overload relay F3 Semiconductor fuses for G1 G2 Frequency converter K1 Main contactor for K2 Main contactor for converter K3 Motor contactor for K4 Motor contactor for converter M1 Three-phase asynchronous motor 4.3 Power factor correction capacitors should be switched out of the motor feeder circuit during the starting phase, since the wave form distortion resulting from the starting may cause them to become overloaded and/or damaged (*Fig. 4.5). The motor running output relay may be used to reconnect the capacitors after the motor has run up to speed. The power factor correction capacitors must never be connected between the and the motor! Fig. 4.5 : Operation of a motor with power factor correction capacitors

23 Motor feeder circuit Table 4.1 : Normal starting, T a = 45 o C Design and selection recommendations for motor feeder circuits incorporating a under normal starting conditions and 45 o C service temperature. Recommendations are made for motor feeders with or without fuses. Q1 Circuit-breaker F1 HRC fuses F2 Overload relay F3 Semiconductor fuses (3NE4) K1 Main contactor K2 Bypass contactor G1 M1 Motor Ambient air temperature T a Fig. 4.6 Configuration of the motor feeder circuit with or without fuses 4 Table 4.1 M1 Motor rated output power Motor rated current at 415 V 7.5 kw G1 (Line Conneced) at 45 o C 3RW2428 (Delta Conneced) F3 Short-circuit protection for (per phase) 100 A SITOR fuse-links 3NE4121 single-pole triple-pole F1 Fuse configuration HRC fuses 3NA3810-7Y K1 Main isolating contactor AC-3 3TF32 F2 Overload relay 2) 3UA5200-2B K1 Fuse-line configuration, 415VMain isolating contactor 3TF32 Q1 (Type 2 for r, Type 1 for Iq) Circuit-breaker 2) 3RV K2 Bypass contactor AC-1 3TF30 M1 Motor rated output power 11 kw 15 kw 22 kw 30 kw Motor rated current at 415 V A 40 A 53 A G1 (Line Conneced) at 45 o C 3RW2429 3RW2430 3RW2431 3RW2432 (Delta Conneced) 3RW2430 F3 Short-circuit protection for (per phase) 125 A 125 A 160 A 160 A SITOR fuse-links 3NE4122 3NE4122 3NE4124 3NE4124 F1 Fuse configuration HRC fuses 3NA3820-7Y 3NA3820-7Y 3NA3824-7Y 3NA3830-7Y K1 Main isolating contactor AC-3 3TF33 3TF44 3TF46 3TF47 F2 Overload relay 2) 3UA5200-2C 3UA5500-2D 3UA5800-2F 3UA5800-2P K1 Fuse-free configuration, 415 V Main isolating contactor 3TF44 1) 3TF44 1) 3TF46 1) 3TF47 1) Q1 (Type 2 for r, type 1 for lq) Circuit-breaker 2) 3RV RV RV RV K2 Bypass contactor AC-1 3TF32 3TF44 3TF46 3TF46 16 A 4.4

24 Motor feeder circuit M1 Motor rated output power 37 kw 45 kw 55 kw 75 kw 90 kw Motor rated current at 415 V 65 A 78 A 96 A 131 A 156 A G1 (Line Conneced) at 45 o C 3RW2433 3RW2434 3RW2435 3RW2436 3RW2437 (Delta Conneced) 3RW2431 3RW2432 3RW2433 3RW2434 3RW2435 F3 Short circuit protection for 315 A 315 A 450 A 500 A 500 A (per phase) SITOR fuse-links 3NE NE NE NE NE F1 Fuse configuration HRC fuses 3NA3832-7Y 3NA3832-7Y 3NA3136-7Y 3NA3140-7Y 3NA3144-7Y K1 Main isolating contactor AC-3 3TF47 3TF50 3TF50 3TF51 3TF52 F2 Overload relay 2) 3UA5800-2U 3UA5830-5B 3UA583-5C 3UA6230-5A 3UA6250-5B K1 Fuse-free configuration, 415 V Main isolating contactor 3TF45 1) 3TF50 1) 3TF50 1) 3TF51 1) 3TF52 1) Q1 (Type 2 for r, Type 1 for Iq) Circuit-breaker 2) 3RV RV RV VL VL K2 Bypass contactor AC-1 3TF46 3TF46 3TF50 3TF51 3TF51 M1 Motor rated output power 110 kw 132 kw 160 kw 200 kw 250 kw Motor rated current at 415 V 189 A 228 A 280 A 345 A 430 A G1 (Line Conneced) at 45 o C 3RW2438 3RW2439 3RW2440 3RW2441 3RW2442 (Delta Conneced) 3RW2436 3RW2437 3RW2438 3RW2439 3RW2440 F3 Short circuit protection for 500 A 710 A 710 A 710 A 2 x 500 A (per phase) SITOR fuse-links 3NE NE NE NE NE F1 Fuse configuration HRC fuses 3NA3252-7Y 3NA3260-7Y 3NA3260-7Y 3NA3365-7Y 3NA3365-7Y K1 Main isolating contactor AC-3 3TF53 3TF54 3TF55 3TF56 3TF57 F2 Overload relay 2) 3UA6230-5C 3UA6230-5C 3UA UA6230-5E 3UA6230-5F K1 Fuse-free configuration, 415 V Main isolating contactor 3TF53 1) 3TF45 1) 3TF55 1) 3TF56 1) 3TF57 1) Q1 (Type 2 for r, Type 1 for Iq) Circuit-breaker 2) 3VL VL VL VL VL K2 Bypass contactor AC-1 3TF52 3TF54 3TF54 3TF56 3TF57 M1 Motor rated output power 315 kw 400 kw Motor rated current at 415 V 540 A 690 A G1 (Line Conneced) at 45 o C 3RW2443 3RW2444 (Delta Conneced) 3RW2441 3RW2442 F34 Short circuit protection for 2 x 500 A 2 x 710 A (per phase) SITOR fuse-links 2 x 3NE x 3NE F1 Fuse configuration HRC fuses K1 Main isolating contactor AC-3 3TF68 3TF69 Q1 (Type 2 for r, Type 1 for Iq) Circuit breakers 3WN61 3WN61 F2 Overload relay 2) 3RB12 3RB12 K2 Bypass contactor AC-1 3TF68 3TF69 1) Iq = 50 ka 2) Normal Starting = class

25 Typical Circuit Diagrams 5. Typical Circuit Diagrams Basic connections with isolated contacts 5 F2 - Overload relay Q1 - MPCB / ACB / MCCB K1/K2 - Main isolating contactors (AC-3 rated) F3 - Semiconductor Fuses (Optional) BH - Command "Ramp-up" BF - Command "Enable" ME - Monitoring signal "In operation" MH - Monitoring signal "End of ramp" Only with I-Option card MU - Monitoring signal "Overload". Note : * With I-Option card only (C. T. connection) ** Fan supply 230 V AC external power supply *** Thermistor or thermostat motor protection 5.1

26 Typical Circuit Diagrams Control through PLC Basic connections for PLC with 24 V = industry logic Q1- MPCB / ACB / MCCB K1 - Main isolating contactor (AC-3 rated) F3 - Semiconductor Fuses (Optional) F2 - Overload relay L - is preferably to be earthed. Remove link if there is a potential difference between L - and PE (max. permissible voltage 60 V) Note : * With I-Option card only (C. T. connection) ** Fan supply 230 VAC external power supply *** Thermistor or thermostat motor protection 5.2

27 Typical Circuit Diagrams Recommended connection : 3RW24 Line Connection for Soft Start (also with I-OPTION card) 5 G1 = F1 = Motor feeder HRC fuses K1 = Main isolating contactor (AC-3 rated) F3 = Semiconductor fuses (Optional) K3 = Bypass contactor (Optional) S1 = OFF push button (Momentary command) S2 = ON push button (Momentary command) F2 = Overload relay Note : * With I-Option only (C. T. connection) ** Fan supply 230 VAC external power supply 5.3

28 Typical Circuit Diagrams Recommended connection : 3RW24, Delta Connection for Soft Start (also with I-Option card) G1 = F1 = Motor feeder HRC fuses K1 = Main isolating contactor (AC-3 rated) F3 = Semiconductor fuses (Optional) K3 = Bypass contactor (Optional) S1 = OFF push button (Momentary Command) S2 = ON push button (Momentary Command) F2 = Overload relay *MU - only with I-Option card Note : * With I-Option only (C. T. connection) ** Fan supply 230 VAC external power supply 5.4

29 Typical Circuit Diagrams Recommended connection : 3RW24, Line Connection Soft Start and Soft Stop (also with I-Option card) 5 G1 = F1 = Motor feeder HRC fuses K1 = Main isolating contactor (AC-3 rated) F3 = Semiconductor fuses (Optional) F2 = Overload relay K3 = Bypass contactor (Optional) S1 = OFF push button (Momentary Command) S2 = ON push button (Momentary Command) K2 = Auxiliary contactor (4 NO) Note : * With I-Option only (C. T. connection) ** Fan supply 230 VAC external power supply 5.5

30 Typical Circuit Diagrams Recommended connection : 3RW24, Line connection as a Soft Start and Soft Stop for reversing application G1 = F1 = Motor feeder HRC fuses F3 = Semiconductor fuses (Optional) K1f = Main isolating contactor in forward direction K1R = Main isolating contactor in reverse direction F2 = Overload relay ON1 = Forward direction ON2 = Reverse direction K3 = Bypass contactor (Optional) K2f = Auxiliary contactor (4NO + 4NC) K2R = Auxiliary contactor (4NO + 4NC) S1 = OFF push button (Momentary Contact) S2.0 = ON push button S2.1 (Momentary Contact) Note : * With I-Option only (C. T. connection) ** Fan supply 230 VAC, external power supply 5.6