Motor Terminology
C
"C"
Flange: 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.
Canopy Cap (Dripcover): 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.)
Capacitor: 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.
Capacitor Motor: 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.
Capacitor Start: 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 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.
Clutch: A mechanical device for engaging and disengaging a
motor often used when many starts and stops are required.
Conductor: A material, such as copper or aluminum, which offers
low resistance or opposition to the flow of electric current.
Conduit (Condulet) Box: The metal container usually on the side
of the motor where the stator (winding) leads are attached to leads going to the
power supply.
Cogging: 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.
Commutator: 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.
Constant Horsepower: 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.
Constant Torque: 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.
Constant Speed: A DC motor which changes speed only slightly
from a no load to a full load condition. In AC motors, these are synchronous
motors.
Core: 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.
Coupling: The mechanical connector joining the motor shaft to
the equipment to be driven.
Current: 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.