Electric Motor Terms

Air-over: Motors for fan or blower service and cooled by the air stream from the fan or blower.

Alternating Current (AC): This is the standard power supply available in homes, factories, or farms, etc.

Amperes: Measure of current flow in an electrical circuit.

Ambient: The temperature of the space around the motor. Most motors are designed to operate in an ambient not over 40 degrees C


Sleeve: Preferred where low noise is important as on fan and blower motors. Unless otherwise stated, sleeve bearing motors can be mounted in any position, including shaft-up or shaft-down.

Ball: Used where high shaft load (radial or axial thrust load) capacity is required or where periodic lubrication is impractical.

Blower Wheel Types:

Single Inlet,Galvanized Steel – Typical applications include fan coil units, room air conditioners, draft inducers, power burners, flue exhaust, furnaces, heaters, condensers and small appliances.

Double Inlet,Aluminum with Steel Hubs – Designed to accomodate higher horsepower and temperature requirements.

Double Inlet,Direct Drive Galvanized – Designed to accomodate higher horsepower and temperature requirements. With Two Inlets.

Double Inlet, Two Hubs, Belt Drive, Galvanized Steel – Designed to accomodate higher horsepower and temperature requirements. With Two Inlets and Two Hubs.

BTU: British Thermal Unit. The quantity of heat needed to raise the temperature of one pound of water one degree Fahrenheit at sea level; approximately the amount of heat given off by burning one wooden match.

Bubble Point: A term used with new refrigerant blends to indicate the refrigerant pressure / temperature relationship at the outlet of the condenser (i.e., liquid pressure). Used when measuring for subcooling on refrigerant blends with temperature glide.

Canadian Standards Association: Sets safety standards for motors and other electrical equipment used in Canada. Most all motors in this catalog meet CSA standards and the CSA logo is displayed on the nameplate.

CFM: Cubic Feet Per Minute. A standard air flow quantification used to describe air flow across coils and through ducted fan systems.

Change of State: The change of a substance from one form to another, resulting from the addition or removal of heat. Changes of state due to the addition of heat:liquid to gas (evaporation), solid to gas (sublimation). Changes of state due to the removal of heat: liquid to solid (freezing), gas to liquid (condensation)

Condensing: The change of state from a gas to a liquid. Heat is rejected during this process.

Dew Point: A term used with new refrigerant blends to indicate the refrigerant pressure/temperature relationship at the outlet of the evaporator (i.e., vapor pressure). Used when measuring for superheat on refrigerant blends with temperature glide.

Direct Current (DC): Type of power supply available from batteries, generators (not alternators) or a rectified source used for special-purpose applications.

Efficiency: A measurement of how effectively a motor turns electrical energy into mechanical energy.

Enclosure: The term used to describe the motor housing. Common Types are:

Open: Ventilation openings in end shields and /or shell to permit passage of cooling air over and around the windings. Location of openings not restricted. for use indoors, in fairly clean locations.

Dripproof: Ventilation openings in end shields and shell placed so drops of liquid falling within an angle of 15 degrees from vertical will not affect performance. Normally used indoors, in fairly clean, dry locations.

Totally Enclosed: No openings in the motor housing (but not air-tight). Used in locations which are dirty, oily etc. Two types are:

Totally enclosed fan cooled: Includes an integral fan to blow cooling air over the motor

Totally enclosed non-ventilated: Not equipped with a fan for external cooling. Depends on covection air for cooling.

Explosion-proof: A special enclosed motor designed to withstand an internal explosion of specified gases or vapors, and not allow the internal flame or explosion to escape. Usually available as non-ventilated (EPNC) in smaller ratings (below 1/3 HP) and fan-cooled (EPFC) in larger ratings. Explosion-proof motors are labeled to meet UL and NEC requirements.

Evaporation: The change of state from liquid into a gas. Heat is absorbed during this process.

Frame or Frame Size: Refers to NEMA standardized motor mountings and shaft dimensions.

Full Load Amperes: Line current (amperage) drawn by a motor when opening at rated load and voltage on motor nameplate. Important for proper wire size selection and motor stater heater selection.

Heat Pump: compression cycle system used to supply heat or cooling to a temperature-controlled space.

Heat Pump Balance Point: The outdoor temperature at which heating capacity of a heat pump in a particular installation is equal to the heat loss of the conditioned area.

Hertz: Frequency, in cycles per second, of AC power; usually 60Hz. in USA, 50 Hz overseas.

High Side: Parts of a refrigeration system which are under condensing or high pressure. Typically from the compressor piston discharge valves to the termostatic expansion valve (TXV).

Horsepower: Output power rating of the motor.

Insulation: In motors, classified by maximum allowable operating temperature: Class A = 105 C, Class B = 130 C, Class F = 155 C, Class H = 180 C.

Latent Heat: Heat energy absorbed in the change of state of a substance (melting, evaporization, fusion) without a change in temperature.

Liquid Line: The tube or pipe that carried liquid refrigerant from the condenser (king valve) to the refrigerant control mechanism (TXV).

Low Side: The portion of a refrigeration system which is at evaporating pressure. Typically, from the thermostatic expansion valve (TXV) to compressor piston suction valves.

Motor Types: Classified by operating characteristics and or type of power required, the AC induction motor is the most common type. Speed remains relatively constant as load changes. There are several kinds of AC induction motors.

For single-phase operation:

Shaded pole: Low starting torque, low cost. Usually used in direct-drive fans and blowers.

Permanent split capacitor: Performance and applications similar to shaded pole but more efficient, with lower line current and higher horsepower rating.

Split-phase start, induction run (or split phase): Moderate starting torque, high breakdown torque. Used on easy-starting equipment, such as belt-driven fans and blowers, grinders, centrifugal pumps, etc.

Capacitor start: High starting and breakdown torque, medium starting current. Used on hard-starting applications; compressors, positive displacement pumps, farm equipment, etc.

Capacitor start, capacitor run: Performance and applications similar to capacitor-start, induction-run, except higher efficiency. Generally used in higher single-phase HP ratings or energy saver designs.

Three-phase: Operate on 3-phase power only. Higher starting and breakdown torque, high efficiency, medium starting current, rugged design, long life. For all types of industrial uses.

National Electrical Code: A code for safeguarding persons and property from the hazards arising from the use of electricity. Sponsored by the National Fire Protection Association. Used by insurance inspectors and by many government bodies regulating building codes, etc.

NEMA: This organization establishes certain voluntary industry standards relating to motors; such as operating characteristics, terminology, basic dimensions, ratings and testing.

Refrigerant: Substance used in a refrigerating system. It absorbs heat in the evaporator by a change of state from a liquid to a gas. It releases its heat in the condenser as the substance returns from the gaseous state to a liquid state.

RH: Relitive Humidity. The percentage of moisture in the air as compared to the amount of moisture in fully-saturated air (i.e., 100% humidity)at the same pressure and temperature conditions.

Sensible Heat: Heat energy which causes a change in the temperature of an object. Sensible heat can be felt.

Subcooling: The difference between the measured liquid line temperature of a refrigerant and it’s condensing temperature at the same pressure.

Superheat: The difference between the measured suction line temperature of a refrigerant vapor and its normal boiling temperature at the same pressure.

Temperature Glide: A term used with the new refrigerant blends to give the range of condensing or evaporating temperatures when the pressure remains constant.

Temperature Rise: The amount by which a motor, operating under rated conditions, is hotter than its sur­rounding ambient temperature.

Thermal Protection: A protective device, built into the motor, used to sense excessive (overload) temperature rise and/or current. These devices disconnect the motor from its power source or operate through a control circuit.

Basic types:

Automatic-Reset: After motor cools, this line-interrupting protector automatically restores power. Should not be used where unexpected restarting would be hazardous.

Manual-Reset: This line interrupting protector has an external button which must be pushed to restore power to motor. Use where unexpected restarting would be hazardous, as on saws, conveyors, compres­sors, etc.

Resistance Temperature Detectors: Preci­sion-calibrated resistors mounted in the motor, used in conjunction with instrument supplied by customer to detect high temperatures.

Thermostat: Protector, which is temperature sensing only, is mounted on the stator winding. Two leads from the device must be connected to a control circuit which initiates corrective action.

Torque: Twisting or turning force produced by motor.

Starting Torque: The amount of turning force produced by a motor as it begins to turn from standstill and accelerate. (Sometimes called locked rotor torque.)

Full-Load Torque: This is the amount of torque produced by a motor when it is running at rated full-load speed at rated horsepower

TXV: Thermostatic Expansion Valve. A control valve that measures and maintains a constant superheat in the evaporator. It responds to a combination of three forces: evaporator pressure, spring tension, and bulb pressure.

UL(Underwriters Laboratories Inc.): An independent testing organization that sets safety standards for motors and other electrical equipment.

V-Belt Types:

Classical V-Belts – Special belts for integral horsepower drives. They are manufactured with high quality components using the ORV (Optibelt Rotary Vulcanization) process.

Light Duty V-Belts – Special belts for fractional drives with smaller diameter sheaves with loads and service requirements within the capacity of single belts.

Molded Cogged Raw Edge V-Belts – Can be used in place of conventional wrapped belts on drives having unusual features such as extreamly small sheave diameters, high belt speeds and unusual power transmission requirements.

Wedge Belts – The use of superior materials and the compact design has made these belts economical and efficient. They can transmit two to three times more hp/kW than classical V-Belts with the same top width. Drives with power ratings up to 2600 hp are not unusual.

Voltage: Voltage is a unit of electromotive force which applied to conductors will produce current in the conductors.

Watts: A unit of electrical power equal to: Current * Voltage 746 watts = 1 horsepower (HP)