MOTOR TERMINAL CONNECTIONS

Motor Classification Most of the industrial machines in use today are driven by electric motors Motors are classified according to the type of power used (AC or DC) and the motors principle of operation

FAMILY TREE OF MOTOR TYPES

Motor Standards IEEE Institute of Electrical and Electronics Engineers Establishes the standard for motor testing and test methodologies NEMA National Electrical Manufacturers Association Prepares the standards for motor performance and classifications

DC Motor Connections DC Motors 1. Used in industrial applications because the speed-torque relationship can easily be varied 2. Speed can be controlled smoothly down to zero, immediately followed by acceleration in the opposite direction

DC Motor Connections DC Motors 3. Can supply five times the rated torque without stalling 4. Dynamic braking or Regenerative braking can be obtained on applications requiring quick stops thus limiting the need of mechanical brake

AC Motor Connections The AC induction motor is the dominant motor technology in use today Representing more than 90 percent of installed motor capacity.

AC Motor Connections Available in single-phase and three-phase configurations, in sizes ranging from fractions of a horsepower to tens of thousands of horsepower. They may run at fixed speeds most commonly 900, 1200, 1800, or 3600 rpm or be equipped with an adjustablespeed drive.

MOTOR NAMEPLATE AND TERMINOLOGY

Motor Nameplate Contains important information about the connection and use of the motor. An important part of making motors interchangeable is ensuring that nameplate information is common among manufacturers.

Required Nameplate Information Motor Manufacture Voltage Rating Current Rating Line Frequency Phase Rating Motor Speed Ambient Temperature

Required Nameplate Information Temperature Rise Insulation Class Duty Cycle Horse Power Rating Code Letter Design Letter Service Factor

Required Nameplate Information Motor Enclosure Frame Size Efficiency Power Factor Thermal Protection Connection Diagram

Guide to Motor Terminology Across-the-line A method of motor starting. Connects the motor directly to the supply line on starting or running. (Also called full voltage.) Automatic starter A self-acting starter. Completely controlled by the master or pilot switch or some other sensing device. Auxiliary contact The contact of a switching device in addition to the main circuit contacts. Operated by the contactor or starter.

Guide to Motor Terminology Contactor A type of relay used for power switching. Jog Momentary operation. Small movement of a driven machine. Locked-rotor current Measured current with the rotor locked and with rated voltage and frequency applied to the motor.

Guide to Motor Terminology Low-voltage protection (LVP) Magnetic control only; not automatic restarting. A three-wire control. A power failure disconnects service; when power is restored, manual restarting is required.

Guide to Motor Terminology Low-voltage release (LVR) Magnetic control only; automatic restarting. A two-wire control. A power failure disconnects service; when power is restored, the controller automatically restarts. Magnetic contactor A contactor that is operated electromechanically. Multispeed starter An electric controller with two or more speeds (reversing or nonreversing) and full or reduced voltage starting.

Guide to Motor Terminology Overload relay Running over-current protection. Operates on excessive current. It does not necessarily provide protection against a short circuit. It causes and maintains interruption of the motor from a power supply. Plugging Braking by reverse rotation. The motor develops retarding force. Push button A master switch that is a manually operable plunger or button for actuating a device, assembled into pushbutton stations.

Guide to Motor Terminology Reduced voltage starter Applies a reduced supply voltage to the motor during starting. Relay Used in control circuits and operated by a change in one electrical circuit to control a

Guide to Motor Terminology Remote control Controls the function initiation or change of electrical device from some remote point. Selector switch A manually operated switch that has the same construction as push buttons, except that rotating a handle actuates the contacts. The rotating cam may be arranged with incremental indices so that multiple positions can be used to select exclusive operations. Slip The difference between the actual speed (motor rpm) and synchronous speed (rotation of the magnetic field).

Guide to Motor Terminology Starter An electric controller used to start, stop, and protect a connected motor. Timer A pilot device, also considered a timing relay, that provides an adjustable time period to perform its function. It can be motor driven, solenoid actuated, or electronically operated. Torque The twisting or turning force that causes an object to rotate. There are two types of torque that are considered for looking at motors: starting torque and running torque.

MANUAL AND MAGNETIC MOTOR STARTER

Manual Starter

Manual Starter Very basic way to supply power to a motor. Manual control circuit is a circuit that requires the operator to control the motor directly at the location of the starter. Dotted line across the contacts designates a manual starter.

Manual Starter Manual starters are operated by the manual start/stop mechanism located on the front of the starter enclosure. The start/stop mechanism moves all three contacts at once to close (start) or open (stop) the circuit to the motor. The National Electrical Code requires that a starter not only turn a motor on and off but also protect it from overloads.

Manual Starter The three thermal overload protective devices are installed to mechanically trip open the starter contacts when an overload condition is sensed. Manual three-phase starters are used in low horsepower applications such as drill presses and table saws where remote pushbutton control is not required.

Magnetic Starter

Magnetic Starter Magnetic motor starters allow a motor to be controlled from any location. When the starter coil is energized, the three main contacts as well as the holding contact close. Should an overload condition occur, the normally closed OL relay contact would open.

Magnetic Starter In addition to the power circuit, the manufacturer provides some control circuit wiring. In this case the prewired control circuit wiring consists of two connections to the starter coil. One side of the starter coil is factory wired to the overload relay contact and the other side to the holding contact.

Types of Magnetic Control Circuits

Types of Magnetic Control Circuits Two-wire control circuit Provides low-voltage release but not low-voltage protection The starter deenergizes during power interruption but also reenergizes if the control devices remains closed during power restoration

Types of Magnetic Control Circuits

Types of Magnetic Control Circuits Three-wire control circuit Provides low-voltage protection The starter will drop out during power interruption but will not pick up during power restoration

MOTOR CONTROL DEVICES

Guessing Game!

Manually Operated Switches A control device is a component that governs the power delivered to an electrical load

I. Primary and Pilot Control Devices

I. Primary and Pilot Control Devices Primary control device such as motor contactor, starter or controller connects the load to the line Pilot control device such as relay or switch contact Used to activate the primary control device

II. Toggle Switches A manually operated switch is one that is controlled by hand The toggle switch is an example

II. Toggle Switches Uses a mechanical lever mechanism to implement a positive snap action for switching of electrical contacts Note: Electrical ratings for switches are expressed in terms of the maximum interrupting voltage and current they can safely handle

III. Pushbutton Switches

III. Pushbutton Switches Commonly used in motor control applications to start and stop motors, as well as to control and override process functions Operates by pressing a button that opens or closes contacts

IV. Pilot Lamp

IV. Pilot Lamp Provide visual indication of the status for many motorcontrolled processes permitting personnel at remote locations to observe the current state of the operation. Used to indicate whether or not a motor is operating. Pilot lights are available in both full-voltage and lowvoltage types.

V. Selector Switch

V. Selector Switch Similar to a push button Rotated to open and close contacts of the attached contact block

VI. Drum Switch

VI. Drum Switch Consists of a set of moving contacts and a set of stationary contacts that open and close as the shaft is rotated Reversing drum switches are designed to start and reverse motors by connecting them across the line

MECHANICALLY OPERATED SWITCHES Controlled automatically by factors such as pressure, position, and temperature

I. Limit Switches

I. Limit Switches designed to operate only when a predetermined limit is reached, and usually actuated by contact with an object such as a cam.

I. Limit Switches Lever type Fork Lever Wobble stick Push Roller type

II. Temperature Control Devices Temperature control devices (thermostats) monitor the temperature or changes in temperature for a particular process. Temperature switches open or close when a designated temperature is reached. Temperature control devices are used in heating or cooling applications where temperature must be maintained within preset limits.

III. Pressure Switches Used to monitor and control the pressure of liquids and gases. Commonly used to monitor a system and, in the event that pressure reaches a dangerous level, open relief valves or shut the system down.

III. Pressure Switches The three categories of pressure switches used to activate electrical contacts are positive pressure, vacuum (negative pressure), and differential pressure.

IV. Flow and Float Switches A float switch is used to sense the height of a liquid. Float switches provide automatic control for motors that pump liquid from a sump or into a tank.

IV. Flow and Float Switches A flow switch is used to detect the movement of air or liquid through a duct or pipe.

SENSORS Controlled automatically by factors such as pressure, position, and temperature

I. Proximity Sensor Proximity sensors detect the presence of an object without physical contact. Detection of the presence of solids such as metal, glass, and plastics, as well as most liquids, is achieved by means of a sensing magnetic or electrostatic field.

II. Photoelectric Sensors Optical control device that operates by detecting a visible or invisible beam of light, and responding to a change in the received light intensity. Composed of two basic components: a transmitter (light source) and a receiver (sensor)

III. Hall Effect Sensors Hall effect sensors are used to detect the proximity and strength of a magnetic field. When a current-carrying conductor is placed into a magnetic field, a voltage will be generated perpendicular to both the current and the field( Hall effect).

IV. Ultrasonic Sensors Operates by sending highfrequency sound waves toward the target and measuring the time it takes for the pulses to bounce back. The time taken for this echo to return to the sensor is directly proportional to the distance or height of the object because sound has a constant velocity.

V. Temperature Sensors THERMOCOUPLE sensor that measures temperature. operate on the principle that when two dissimilar metals are joined, a predictable DC voltage will be generated that relates to the difference in temperature between the hot junction and the cold junction

V. Temperature Sensors RESISTANCE TEMPERATURE DETECTORS wire-wound temperature-sensing devices that operate on the principle of the positive temperature coefficient (PTC) of metals. (electrical resistance of metals is directly proportional to temperature)

V. Temperature Sensors THERMISTOR thermally sensitive resistors that exhibit changes in resistance with changes in temperature.

V. Temperature Sensors INTEGRATED CIRCUIT use a silicon chip for the sensing element. principle of operation is based on the fact that semiconductor diodes have temperaturesensitive voltage versus current characteristics.

VI. Velocity and Position Sensors TACHOMETER provide a convenient means of converting rotational speed into an analog voltage signal that can be used for motor speed indication and control applications. small AC or DC generator that develops an output voltage (proportional to its rpm) whose phase or polarity depends on the rotor s direction of rotation.

VI. Velocity and Position Sensors MAGNETIC PICKUP essentially a coil wound around a permanently magnetized probe. When a ferromagnetic object, such as gear teeth, is passed through the probe s magnetic field, the flux density is modulated. This induces AC voltages in the coil.

VI. Velocity and Position Sensors ENCODER used to convert linear or rotary motion into a binary digital signal. used in applications such as robotic control where positions have to be precisely determined.

VII. Flow Measurement TURBINE FLOWMETERS a popular means of measurement and control of liquid products in industrial, chemical, and petroleum operations. Turbine flowmeters, like windmills, utilize their angular velocity (rotation speed) to indicate the flow velocity.

VII. Flow Measurement TARGET FLOWMETERS inserts a target, usually a flat disk with an extension rod, oriented perpendicularly to the direction of the flow. measure the drag force on the inserted target and convert it to the flow

VIII. Magnetic Flowmeters also known as electromagnetic flowmeters or induction flowmeters, obtain the flow velocity by measuring the changes of induced voltage of the conductive fluid passing across a controlled magnetic field.

ACTUATORS any device that converts an electrical signal into mechanical movement.

I. Relay An electromechanical relay is a type of actuator that mechanically switches electric circuits. provides control logic by switching multiple control circuits used for controlling low-current pilot loads such as contactor and starter coils, pilot lights, and audible alarms.

II. Solenoids a device that uses electrical energy to magnetically cause mechanical control action. A solenoid consists of a coil, frame, and plunger (or armature) When the coil is energized, it produces a magnetic field that attracts the plunger, pulling it into the frame and thus creating mechanical motion.

III. Solenoid Valves electromechanical devices that work by passing an electrical current through a solenoid, thereby changing the state of the valve. a combination of a solenoid coil operator and valve, which controls the flow of liquids, gases, steam, and other media. When electrically energized, they either open, shut off, or direct the flow of media.

IV. Stepper Motors Operate differently than standard types, which rotate continuously when voltage is applied to their terminals. The shaft of a stepper motor rotates in discrete increments when electrical command pulses are applied to it in the proper sequence. The amount of rotation is directly proportional to the number of pulses and the speed of rotation is relative to the frequency of those pulses.

V. Servo Motors Operate in closed-loop mode, whereas most stepper motors operate in open-loop mode. Open loop is control without feedback, for example, when the controller tells the stepper motor how many steps to move and how fast to move, but does not verify where the motor is. Closed-loop control compares speed or position feedback with the commanded speed or position and generates a modified command to make the error smaller.