Safety Working with LV Drives

Transcription

1 US1008e_LV Drive Safety_C, April 2009 Safety Working with LV Drives

2 Intended Audience Only qualified electricians and engineers are allowed to install and maintain a LV Drive Students of this training are expected to know standard electrical wiring practices, electrical components and electrical schematic symbols This training module is intended to provide an overview / summary of safe working practices and recommendations for working with or around Low Voltage (LV) Drives This training module does not provide process details or specific safety procedures for all situations or all applications of LV Drives. It is the student s responsibility to act and work as most appropriate and safely for each situation as defined by local, regional and national codes. Slide 2

3 Objectives After completing this module, you will be able to Define the safety risks associated with on-site work risks to yourself, risks to other personnel and risks to systems at the same site Apply and use Lock-Out / Tag-Out equipment and processes Define the safety risks associated with LV Drives and how to mitigate those risks Slide 3

4 Prerequisites basic knowledge of AC and DC voltage basic knowledge of electronics Glossary of special terms used in this training module PE Potential Earth LOTO log out / tag out IFS inhibit false start PMSM permanent magnet synchronous motor UPS uninterruptible power supply Slide 4

5 Safety Incidents Incidents happen because of: 1. Mechanical / component failure 2. Poor communication / understanding 3. Carelessness / abnormal behavior 4. Risk taking / complacency 5. Stored electrical or mechanical (kinetic) energy Try to think of times and or incidents when 1 or more of these factors could have or did resulted in an incident. Slide 6

6 On-site work safety risks Table of Contents Slips, Trips and Falls Environmental risks Personal Protective Equipment (PPE) Use the right tools Electric shock prevention of Lock Out / Tag Out Potential voltages of LV Drives Unexpected operation of the drive and equipment Other work occurring on site and potential risks Slide 7

7 Slips, Trips and Falls Slip, Trips and Falls are the most common cause of injury Be aware of your surroundings at all time Remove excess clutter for your working area Slow down, carry the appropriate load, maintain visibility Do not use equipment outside of it s intended use garbage cans are not step stools Slide 8

8 Environmental risks Personal Protective Equipment (PPE) Wear the appropriate PPE per the environment and as required by the site Always wear eye and ear protection Protective foot wear should always be used Other Considerations falling objects dust, gases extra Follow all local safety instructions Slide 9

9 Environmental risks Personal Protective Equipment (PPE) Arc Flash is the result of a rapid release of energy due to an arcing fault between a phase bus bar and another phase bus bar, neutral or a ground An arc is produced by flow of electrical current through ionized air after an initial flashover or short circuit Arc Flash PPE requirements are determined by the site and site owning company. Each company determines its guidelines, process and equipment for arc flash protection Slide 10

10 Environmental risks Use the right tools Multi-meter 1000V CAT III (EN ) 1000V probes and test leads Current measurement clamp Oscilloscope 1000V CAT II min 1000V probes and test leads Protective gloves with appropriate ratings ESD Static straps to be worn only when voltage is off and handling electronic components Slide 11

11 Electric Shock prevention of Dangerous voltages LV Drives inherently involve multiple points of high potential voltage. Care must be taken at all times when working with and around power equipment main circuit potentials auxiliary circuit voltages ensure the safe level by measurement external voltage sources Slide 12

12 Electric Shock prevention of Lock-Out / Tag-Out The OSHA standard for The Control of Hazardous Energy (Lockout/Tagout), Title 29 Code of Federal Regulations (CFR) Part , addresses the practices and procedures necessary to disable machinery or equipment, thereby preventing the release of hazardous energy while employees perform servicing and maintenance activities. The standard outlines measures for controlling hazardous energies - electrical, mechanical, hydraulic, pneumatic, chemical, thermal, and other energy sources Required in applications of 50V and greater Slide 13

13 Electric Shock prevention of Drive Safety Basics Practice Lock-Out / Tag-Out procedures Never Work Alone Remove all Loose-fitting Clothing, Jewelry & Metal Items NO ESD wrist straps when power is applied Ensure Drive s Internals Are Free From All Foreign Matter Approach Drive as if it were Live (always perform a voltage check with an approved measurement device) Ensure Motor Leads are Connected to Motor Terminals and Main Power is Connected to Input Terminals Ensure Power Supply (230, 480Vac) Matches Drive s Input Voltage Rating Ensure Motor Is Capable Of Running Mechanically Use (1) Hand During Start-Up Test output voltage phase to phase, phase to ground Slide 14

14 Electric Shock prevention of LV Drive Common Power Terminals Drive power terminal labeling: low voltage drives power terminals are labeled to indicate input power, DC Bus power, brake chopper and output power (motor connection) Input power terminals are typically labeled with one or more of the following; U1, V1, W1 Output power terminals are typically labeled with one or more of the following; U2, V2, W2 DC Bus power terminals are not available on all LV Drives, for drives that included the terminals they are labeled; UDC+, UDC- Brake Chopper power terminals are not available in all LV Drives, for drives that include the terminals they are labeled; BRK+, BRK- L1, L2, L3 T1, T2, T3 DC+, DC- R+, R- R, S, T U, V, W L, N Slide 15

15 Electric Shock prevention of LV Drive Grounding ABB drives Grounding & Cabling of the Drive System 3AFY Traditional grounding is based on electrical safety. It provides personal safety in most circumstances and limits material damages due to electrical faults. All LV Drives require Grounding Proper grounding must be checked before proceeding to service or apply power to any LV Drive equipment Slide 16

16 Electric Shock prevention of LV Drive potential voltage Supply Line = 120Vac 1Φ to 690Vac 3Φ Drive Output = 0 to 700Vac 3Φ DC Bus = 160Vdc to 1000Vdc example: 480Vac Line = ~650Vdc bus U1 V1 W1 U2 V2 W2 R- UDC+ R+ UDC- Slide 17

17 Electric Shock prevention of LV Drive potential voltage LV Drives may have high potential voltages even when they are not running Input power is 208Vac to 690Vac DC Bus is 290Vdc to 1000Vdc Power output (motor connection) can still be live even when the drive is off due to motor coasting to stop, mechanical connection to other driven section and due to high potential to PE or ground Slide 18

18 Electric Shock prevention of LV Drive potential voltage LV Drives may have high potential voltages even when they are disconnect from supply line The DC Bus can remain live for up to 5 minutes due to capacitor discharge The drive may maintain the DC Bus by using the mechanical energy from the motor as long as the motor is turning Motor voltage will be present as long as the motor is turning Slide 19

19 Electric Shock prevention of LV Drive potential voltage Always assume the drive is live check before service Check input voltage all 3 phases to ground Check DC Bus if terminals available Check motor terminals at the drive, all 3 phases to ground U1 V1 W1 U2 V2 W2 V ~ R- UDC+ R+ UDC- V = V ~ Slide 20

20 Electric Shock prevention of Permanent magnet motor drives Permanent magnet motors generate potential electrical energy when they are mechanically rotated. Power does not need to be applied to a PM motor for there to be potential electrical energy. DC-link Supply Inverters... 3-phase supply PMSM PMSM PMSM Slide 21

21 Electric Shock prevention of LV Drive potential voltage Even when all power terminals are confirmed at low voltage there is still potential for high voltage to exist from External supplies The relay outputs support up to 230Vac control power. This voltage is supplied from a separate source and must be disabled or disconnected Slide 22

22 Unexpected Operation Warning some LV Drives can be configured to START as soon as power is applied Ensure the machine is safe to operate before applying power When ever possible employ start interlock / start inhibit functionality available in the LV Drive product used Do not control the LV Drive or motor with the disconnecting device; instead, use the available control circuits such as control I/O, operator panel, or communication control. Eliminate start control signals from I/O and other systems Slide 23

23 Unexpected Operation Emergency Stop Emergency Stop devices should be employed in most LV Drive applications Drives should not be allowed to start when the E-Stop is set All E-Stops related to the systems operation should be included in the Start Inhibit / Interlock circuits of the equipment Slide 24

24 Unexpected Operation Emergency Stop IEC Standard EN includes two emergency operations Emergency Switching Off and Emergency Stop NFPA-79, includes three Emergency Stop categories, we will note two here Emergency Stop categories (Category 0) Immediate Removal of Power (Category 1) Controlled Emergency Stop Slide 25

25 Unexpected Operation Inhibit False Start (IFS) Provides a means to disconnect the motor from power source for personnel safety not for start/stop of the motor does not separate the motor galvanically from the drive Slide 26

26 Other Site Risks In general LV Drives below 75kW or 100Hp are not designed to be field repaired Never attempt to repair a malfunctioning drive; contact the factory or your local authorized service center for replacement LV Drives that are considered repairable may only be serviced or repaired by trained and authorized service personnel; contact the factory or your local authorized service center for support Slide 27

27 7 Steps that save lives 1. Cleary identify work location This may have to be repeated throughout the job 2. Disconnect & secure against reconnection (LOTO) Carry out grounding & short circuiting as appropriate 3. Protect against any other live parts Additional physical barriers MUST be applied (locks, insulating screens, etc.) when live equipment is exposed 4. Take special precautions when close to bare connections 5. Check the installation is dead (no power) 6. Carry out earthing and short circuiting 7. Issue a permit to work as appropriate for the location Which of these steps apply to the work you perform? (circle those that are applicable.) Slide 28

28 Summary Key points of this module On-site work safety risks Approach all equipment as though it were live LV Drives can be live even with input power disconnected Ensure safe voltage levels by measurement Practice proper lock out / tag out procedures Measurement device use at least CAT III 1000V multi-meter use only measurement equipment in good repair / condition Slide 29

29 Reference Materials IEC standards NFPA79 & OSHA standards NEC (National Electric Code) ABB drives Functional Safety, Technical Guide No. 10 3AUA ABB drives Grounding & Cabling of the Drive System 3AFY ABB drives LV Drives product specific User Manuals and Hardware Manuals Slide 30

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