CH-12 E. Motors

electronically commutated motor (ECM)

a programmable brushless DC motor that used electronic switching devices to control polarity and power in stator windings.

permanent split capacitor motor (PSC)

a single-phase induction motor that uses a single run capacitor in series with the start winding throughout the motor's entire operation. it does not use a centrifugal switch or relay. It does NOT use a centrifugal switch or relay to switch off any capacitors or windings.

start winding

Stator windings that are used for motor starting and additional torque. Start windings have smaller diameter wire that run windings, which gives them a higher resistance.

starting terminal

The motor terminal of a hermetic compressor that connects to one end of the start winding. the opposite end of the start winding is connected to the common terminal.

rated voltage

The voltage level where a motor will perform at its best. also called nameplate voltage

motor terminal box

a box mounted on the outside of a motor's frame in which electrical connections are made to control and power the motor

start capacitor

a capacitor used to provide starting torque during the start-up of some single-phase motors. A start-capacitor is dropped out of the motor circuit after the motor starts running.

variable frequency drive

a control circuit that changes the speed of a motor by varying the frequency of the electrical signal supplied to the motor.

run-capacitor

a device that uses a stored electrical charge to boost motor torque while the motor is running. Run capacitors also dissipate heat generated by the motor.

phase splitting

a motor condition where the current flowing through the start winding is out of phase with the current flowing through the run winding. Phase splitting is the means by which single-phase motors create a rotating magnetic field in the stator to cause the rotor to start turning.

dual-voltage motor

a motor that has its stator windings arranged in pairs so that it can be used with two different voltages. Three-phase motors are typically dual voltage motors.

rated full load speed

a motor's speed (RPM) under a full load when both the rated voltage and frequency are supplied

motor nameplate

a plate mounted on the outside of a motor's frame that displays essential motor information

capacitor-start, capacitor run (CSCR) motor

a single-phase induction motor that has a start capacitor and a run capacitor wired in series with the start winding. The run capacitor is kept in the motor circuit during operation to improve the motor's efficiency.

capacitor-start, induction run (CSIR) motor

a single-phase induction motor that has a start capacitor wired in series with the start winding. the start capacitor helps to create high starting torque.

single-phase motor

an AC motor that runs on a single phase of alternating current

common terminal

one of three motor terminals on a hermetic compressor. the common terminal connects to a single line that joins one end of the start winding to one end of the run winding.

run-winding

stator windings that are energized during the entire operation of a motor. run winding are made of larger diameter wire than start windings, which gives them lower resistance.

end bell

the caps or plates at either end of a motor frame that house the bearings and support the rotor.

rated full load amperage (FLA)

the current level at which a motor's full-load torque and horsepower are reached.

locked rotor amperage (LRA)

the current that a motor draws as power is first applied to start turning the rotor

slip

the difference between a motor's synchronous speed and rated full-load speed due to magnetic slippage.

running terminal

the motor terminal on a hermetic compressor that connects to one end of the run winding. the opposite end of the run winding is connected to the common terminal

synchronous speed

the speed (RPM) of the rotating magnetic field in an electric motor's stator. A motor runs at synchronous speed if the speed of the rotor equals the speed of the stator's rotating magnetic field.

stator

the stationary part of an electric motor that is attached to the inside of the motor houseing. the stator can also be called the frame.

counter electromotive force (cemf)

the voltage induced in a running motor by the rotor's magnetic field that has a polarity opposite of the voltage applied to the stator

torque

the work performed by a twisting or turning action,such as a rotating motor shaft

split-phase motor

a single-phase induction motor that uses the different inductance values of its start winding and run winding to produce phase splitting and achieve initial rotation.

shaded-pole motor

a single-phase motor that uses shaded field poles instead of a start winding to produce starting torque. One-third of each stator pole is split from the rest of the pole and wrapped with a copper band or copper wire.

induction motor

an AC motor that operates by using the magnetic field generated in the stator to introduce current in the rotor

ac motor

an electric motor that runs on alternating current

squirrel cage rotor

an electric motor's rotor that is made of metal bars mounted on an iron core.

centrifugal switch

an electrical device mounted on the end of a motor shaft that disconnects the start windings from the motor circuit. the switch is opened and closed by centrifugal force

field pole

an electromagnet in an AC motor's stator whose polarity changes as the flow of current alternates in the field windings

three-phase motor

an induction motor that has three sets of stator windings powered by three phase power. Each set of windings is connected to one phase of the three-phase power source.

built up terminal

electrical terminals that are bolted to a compressor dome. built up terminal make it easier for technicians to install replacement terminals if needed.

rotor

in an electric motor, an axle mounted unit that rotates as the polarities of the stator's field poles change. In some cases, a rotor can also be called the armature.

field winding

in an electric motor, the wires wrapped around the field poles of the stator that create a magnetic field when current flows through them