Magnetic Polarity: It is a fundamental principle of a winding that adjacent poles must be wound to give opposite magnetic polarity. This does not mean that the coils actually have to be wound in this direction before being placed into the stator. It does mean that the winding must be connected so that, if the current proceeds through one pole in a clockwise direction, it must proceed through the next pole in a counterclockwise direction. This principle is used to determine the correctness of connection diagrams.

Measuring System: Consists of an encoder and associated electronics incorporating interpolation, counter, readout and/or data interface.

Mechanical Time Constant (Seconds): In a simple first order system, the time required for the motor's speed to attain 63.2% of its final value for a fixed voltage level. Can be calculated from: where: J is inertia in lb-in./s2 R is resistance in ohms KT is torque constant in lb-in./amp. 8.87 is a conversion factor tM is calculated in seconds.

Medium Motors: Motors in NA 143T to 449T frames.

Meggar Test: A measure of an insulation system's resistance. This is usually measured in megohms and tested by passing a high voltage at low current through the motor windings and measuring the resistance of the various insulation systems.

Microstepping: An electronic technique for increasing a step motor's position resolution and velocity smoothness by appropriately scaling the phase currents. Microstepping is also a technique used to reduce or eliminate the effects of system resonance at low speeds.

Midrange Instability: A phenomenon in which a step motor can fall out of synchronism due to a loss of torque at midrange speeds. The torque loss is due to the interaction of the motor's electrical characteristics and the driver's electronics. Some drivers have circuitry to eliminate or reduce the effects of midrange instability.

Modular Angle Encoder: Angle encoder, consisting essentially of disk and scanning unit assemblies (rotor and stator) which are integrated into a machine or a rotary table.

Moire Principle: Photoelectric scanning method to produce periodic signals using two fine gratings which are closely positioned to each other and have approximately parallel and equally spaced lines.

Motor: A device that takes electrical energy and converts it into mechanical energy to turn a shaft.

MTBF: Mean time between failure, a measurement of reliability.

Multi-Speed Motors: A motor wound in such a way that varying connections at the starter can change the speed to a predetermined speed. The most common multi-speed motor is a two-speed although three- and four-speeds are sometimes available. Multi-speed motors can be wound with two sets of windings or one winding. They are also available with constant torque, variable torque or constant horsepower. Skin temperature identification numbers.

Multiplication: Multiplication is any technique to derive an output resolution greater than the base line count of the encoder. This can be internal or external.

Multiturn Rotary Encoder: Absolute rotary encoder which determines the angular position of the shaft and the number of shaft rotations.


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