Technology / Motors Glossary

Pull-Up Torque: The minimum torque developed by an AC motor during the period of acceleration from zero to the speed at which breakdown occurs. For motors which do not have a definite breakdown torque, the . . . View Full Definition

Random Wound: The standard type of stator winding used in motors under 1,000 volts. The coils are random wound with round wire as opposed to flat form wound coils.

Reactance (Inductive): The characteristic of a coil, when connected to alternating current, which causes the current to lag the voltage in time phase. The current wave reaches its peak later than the voltage wave . . . View Full Definition

Relay: A device that is operative by a variation in the conditions of one electric circuit to effect the operation of other devices in the same or another electric circuit.

Reluctance: The characteristic of a magnetic material which resists the flow of magnetic lines of force through it.

Reluctance Synchronous Motor: A synchronous motor with a special rotor design which directly lines the rotor up with the rotating magnetic field of the stator, allowing for no slip under load. The reluctance motors have . . . View Full Definition

Resilient Mounting: A suspension system or cushioned mounting designed to reduce the transmission of normal motor noise and vibration to the mounting surface. This type of mounting is typically used in fraction . . . View Full Definition

Resistance: The degree of obstacle presented by a material to the flow of electric current is known as resistance and is measured in ohms.

Reversing: Unless otherwise specified, a general-purpose DC motor is reversible. A DC motor can be reversed by changing the polarity of the field or the armature, but not both. When rapid reversing is . . . View Full Definition

Revolutions Per Minute (RPM): The number of times per minute the shaft of the motor (machine) rotates. This is a function of design and the power supply.

Roller Bearing: A special bearing system with cylindrical rollers capable of handling belted applications, too large for standard ball bearings.

Rotating Magnetic Field: The force created by the stator once power is applied to it that causes the rotor to turn.

Rotor: The rotating member of an induction motor made up of stacked laminations. A shaft running through the center and a squirrel cage made in most cases of aluminum which holds the laminations to . . . View Full Definition

Routine: A routine test is a basic test done in the factory to the requirements of NEMA MG1, paragraph 12.51 and IEEE-112-1978 and includes the following measurements: no load current/watts: winding . . . View Full Definition

Screens: Are protection which can be placed over openings in the fan cover on a fan-cooled motor or ventilation openings of a protected motor to help keep out large particles and/or animals, but not . . . View Full Definition

Secondary Winding: Winding which is not connected to the power source, but which carries current induced in it through its magnetic linkage with the primary winding.

Series Dc Motors: Where high starting torques are required for a DC motor, the series motor is used. The load must be solidly connected to the motor and never decrease to zero to prevent excessive motor speed . . . View Full Definition

Service Factor: 1. When used on a motor nameplate, a number which indicates how much above the nameplate rating a motor can be loaded without causing serious degradation, (i.e., a 1.15 S-F can produce 15% g . . . View Full Definition

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