Canopy (Drip Cover): 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 (functions as 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 single-phase motors to start, or in three-phase motors for power factor correction.
Capacitor Motor: A single-phase induction motor with a main winding arranged for direct connection to the power source, and an 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 better 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 since it provides greater reversing ability at less watts input.
Carrier Frequency Method: Scanning method used mainly with magnetic and inductive measuring systems (see dynamic scanning).
CE: This designation shows that a product such as a motor or control meets European Standards for safety and environmental protection. A CE mark is required for products used in most European countries.
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 predetermined 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.
C-face Mounting: A standard NEMA mounting design, where the mounting holes in the face are threaded to receive the mating mount.
Channel: A single channel equals one incremental output.
CIV (Corona Inception Voltage): The minimum voltage amount that begins the process of ionization (corona) of motor windings.
Class B Insulation: A NEMA insulation specification. Class B insulation is rated to an operating (internal) temperature of 130°C.
Class F Insulation: A NEMA insulation specification. Class F insulation is rated to an operating (internal) temperature of 155°C
Class H Insulation: A NEMA insulation specification. Class H insulation is rated to an operating (internal) temperature of 180°C.
Closed Loop: A broadly applied term, relating to any system in which the output is measured and compared to the input. The output is then adjusted to reach the desired condition. In motion control, the term typically describes a system utilizing a velocity and/or position transducer to generate correction signals in relation to desired parameters.
Clutch: A mechanical device for engaging and disengaging a motor. It is often used when many starts and stops are required.
Cogging (Cogging torque): A term used to describe non-uniform angular velocity. Cogging appears as a jerkiness, especially at low speeds.
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.
Commutation: 1. A term which refers to the action of steering currents or voltages to the proper motor phases so as to produce optimum motor torque. In brush type motors, commutation is done electromechanically via the brushes and commutator. In brushless motors, commutation is done by the switching electronics using rotor position information obtained by Hall sensors, a Tachsyn, or a resolver. 2. Commutation of step motors is normally done open loop. Feedback from the motor is not required to hold rotor position precisely.
Complementary: Complementary is the term for two identical periodic signals where one signal is electrically inverted from the other. Example of single channel electrically inverted. Complementary signals are typically generated by inversion of the electrical output from a single channel.
Complete: A complete test is a test which meets the requirements of IEEE-112- 1978. It includes the tests conducted in a Routine Test as well as a full-load heat run; no-load current and watts determination of torques; efficiencies at 125, 100, 75, 50 and 25 percent of full load; power factor at 125, 100, 75, 50 and 25 percent of full load.
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 variable speed is not. 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.
Conductor: A material such as copper or aluminum which offers low resistance or opposition to the flow of electric current.
Conduit 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.
Constant HP (Horse Power): A designation for variable speed motors used for loads requiring the same amount of horsepower regardless of their motor speed during a normal operation.
Constant Speed: A DC motor which changes speed only slightly from a no-load to a full-load condition. For AC motors, these are synchronous motors.
Constant Torque: Refers to loads with horsepower requirements that change linearly at different speeds. Horsepower varies with the speed, i.e., 2/1 HP at 1800/900 RPM (seen on some two-speed motors). Applications include conveyors, some crushers and constant-displacement pumps.
Continuous Rated Current (ICR) (Amperes): The maximum allowable continuous current a motor can handle without exceeding the motor temperature limits.
Continuous Rated Torque (TCR) (lb-in.): The maximum allowable continuous torque a motor can handle without exceeding the motor temperature limits.
Continuous Stall Current (ICS) (Amperes): Amount of current applied to a motor (at locked rotor conditions), which results in rated temperature rise. Refer also to definition of continuous stall torque.
Continuous Stall Torque (TCS) (lb-in.): The amount of torque at zero speed, which a motor can continuously deliver without exceeding its thermal rating. Determined by applying DC current through two windings with rotor locked, while monitoring temperature. Specified with motor windings at maximum rated temperature, with motor in 25 degrees C ambient, mounted to a heat sink. Refer to individual specs for heat sink size.
Controller: A term describing a functional block containing an amplifier, power supplies, and possibly position-control electronics for operating a servomotor or step motor.
Core: The iron portion of the stator and rotor made up of cylindrical laminated electric steel. The stator and rotor cores are concentric and separated by an air gap, with the rotor core being the smaller of the two and inside to the stator core.
Corona: This is the electrical discharge breakdown of a winding through the application of excessive voltage.
Counter Electromotive Force (CF): 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 educe it.
Coupling: The mechanical connector joining the motor shaft to the equipment to be driven.
CSA: Canadian Standards Association like U.L., sets specific standards for products used in Canada.
Current: This time rate of flow of electrical charge and is measured in am (amperes).
Current at Peak Torque (IPK) (Amperes): The amount of input current required to develop "peak torque". This is often outside the linear torque/current relationship.
Current, Rated: The maximum allowable continuous current a motor can handle without exceeding motor temperature limits.
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) AC power is common throughout the US and 50 Hz is common in many foreign countries.
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