Electric Motors Store - Glossary
C - Terms
A type of flange used with close coupled pumps, speed reducers, and similar applications where the mounting holes in the f flange are threaded to receive bolts. Normally the "C" Flange is used where a pump or similar item is to be overhung on the motor. The "C" type flange is a NEMA standard design and available with or without feet.
A protective cover placed on the top of a motor being mounted vertically to protect it from liquids or solids that might drop onto the motor. (It acts similar to an umbrella for the motor.)
A device which, when connected in an alternating-current circuit, causes the current to lead the voltage in time phase. The peak of the current wave is reached ahead of the peak of the voltage wave. This is the result of the successive storage and discharge of electric energy used in 1 phase motors to start or in 3 phase for power factor correction.
A single-phase induction motor with a main winding arranged for direct connection to the power source, and auxiliary winding connected in series with a capacitor. There are three types of capacitor motors: capacitor start, in which the capacitor phase is in the circuit only during starting, permanent-split capacitor, which has the same capacitor and capacitor phase in the circuit for both starting and running; two-value capacitor motor, in which there are different values of capacitance for starting and running.
The capacitor start single phase motor is basically the same as the split phase start, except that it has a capacitor in series with the starting winding. The addition of the capacitor provides a more ideal phase relation and results in greater starting torque with much less power input. As in the case of the split phase motor, this type can be reversed at rest, but not while running unless special starting and reversing switches are used. When properly equipped for reversing while running, the motor is much more suitable for this service than the split phase start as it provides greater reversing ability at less watts input.
CENTRIFUGAL CUTOUT SWITCH
A centrifugally operated automatic mechanism used in conjunction with split phase and other types of single phase induction motors. Centrifugal cutout switches will open or disconnect the starting winding when the rotor has reached a pre-determined speed, and reconnect it when the motor speed falls below it. Without such a device, the starting winding would be susceptible to rapid overheating and subsequent burnout.
A mechanical device for engaging and disengaging a motor often used when many starts and stops are required.
A material, such as copper or aluminum, which offers low resistance or opposition to the flow of electric current.
The metal container usually on the side of the motor where the stator (winding) leads are attached to leads going to the power supply.
A term used to describe non-uniform angular velocity. It refers to rotation occurring in jerks or increments rather than smooth motion. When an armature coil enters the magnetic field produced by the field coils, it tends to speed up and slow down when leaving it. This effect becomes apparent at low speeds. The fewer the number of coils, the more noticeable it can be.
COIL (Stator or Armature)
The electrical conductors wound into the core slot, electrically insulated from the iron core. These coils are connected into circuits or windings which carry independent current. It is these coils that carry and produce the magnetic field when the current passes through them. There are two major types: "Mush" or "random" wound, round wire found in smaller and medium motors where coils are randomly laid in slot of stator core; and formed coils of square wire individually laid in, one on top of the other, to give an evenly stacked layered appearance.
A cylindrical device mounted on the armature shaft and consisting of a number of wedge-shaped copper segments arranged around the shaft (insulated from it and each other. The motor brushes ride on the periphery of the commutator and electrically connect and switch the armature coils to the power source.
COMPOUND WOUND DC MOTORS
Designed with both a series and shunt field winding, the compound motor is used where the primary load requirement is heavy starting torque, and adjustable speed is not required. (See Paralleling) Also used for parallel operation. The load must tolerate a speed variation from full-load to no-load.
Industrial machine applications include large planers, boring mills, punch presses, elevators, and small hoists.
A designation for variable or adjustable speed motors used for loads requiring the same amount of H.P. regardless of their motor speed during normal operation.
Refers to loads whose H.P. requirements change linearly with changing speeds. Horsepower varies with the speed, i.e.- 2/1 HP at 1800/900 RPM. (Seen on some 2-speed motors). Possible applications include conveyors, some crushers, or constant-displacement pumps.
A DC motor which changes speed only slightly from a no load to a full load condition. In AC motors, these are synchronous motors.
The iron portion of the stator and rotor; made up of cylindrical laminated electric steel. The stator and rotor cores are concentric separated by an air gap, with the rotor core being the smaller of the two and inside to the stator core.
COUNTER ELECTROMOTIVE FORCE(CEMF)
The induced voltage in a motor armature, caused by conductors moving through or "cutting" field magnetic flux. This induced voltage opposes the armature current and tends to reduce it.
The mechanical connector joining the motor shaft to the equipment to be driven.
The time rate of flow of electrical charge and is measured in amps (amperes).
CYCLES PER SECOND (HERTZ)
One complete reverse of flow of alternating current per rate of time. (A measure of frequency.) 60 HZ (cycles per second) A.C. power is common throughout the U.S. and 50 HZ is more common in some foreign countries.