Paralleling: When two or more DC motors are required to operate in parallel – that is, to drive a common load while sharing the load equally among all motors – they should have speed-torque characteristics which are identical. The greater the speed droop with load, the easier it becomes to parallel motors successfully. It follows that series motors will operate in parallel easier than any other type. Compound motors, which also have drooping speed characteristics (high regulation), will generally parallel without special circuits or equalization. It may be difficult to operate shunt or stabilized-shunt motors in parallel because of their nearly constant speed characteristics. Modifications to the motor control must sometimes be made before these motors will parallel within satisfactory limits.

Part Winding Start Motor: Is arranged for starting by first energizing part of the primary winding and subsequently energizing the remainder of this winding in one or more steps. The purpose is to reduce the initial value of the starting current drawn or the starting torque developed by the motor. A standard part winding start induction motor is arranged so that one-half of its primary winding can be energized initially and subsequently the raining half can be energized, both halves then carry the same current.

Peak Torque (Tpk) (lb-in.): The maximum torque a brushless motor can deliver for short periods of time. Operating PacTorq motors above the maximum torque value can cause demagnetization of the rare-earth magnets. This is an irreversible effect that will alter the motor characteristics and degrade performance. This is also known as peak current. Not to be confused with system peak torque, which is often determined by amplifier peak current limitations, where peak current is typically two times continuous current.

Permanent Magnet Synchronous (PMR) (Hysteresis Synchronous): A motor with magnets bedded into the rotor assembly, which enable the rotor to align itself with the rotating magnetic field of the stator. These motors have zero slip (constant speed with load) and provide higher torque, efficiency and draw less current than comparable reluctance synchronous motors.

Phase Evaluation: Method of determining position by detecting the phase between alternating voltages having a slight variation in frequency.

Phase Grating Scale: Scale with step grating which diffracts the transmitted or reflected light into 2 or more orders.

Plug Reversal: Reconnecting a motor's winding in reverse to apply a reverse braking torque to its normal direction of rotation while running. Although it is an effective dynamic braking means in many applications, plugging produces more heat than other methods and should be used with caution.

Polarization Text: A ratio of one-minute meggar test to ten-minute meggar test. Used to detect contaminants in winding insulation done typically on high voltage V.P.I. motors, which are tested by water immersion.

Poles: 1. Refers to the number of magnetic poles arranged on the rotor of the brushless motor. Unlike an AC motor, the number of poles has no direct relationship to the base speed of the motor. 2. In an AC motor, refers to the number of magnetic poles in the stator winding. The number of poles determines the motor's speed. In a DC motor, refers to the number of magnetic poles in the motor. They create the magnetic field in which the armature operates (speed is not determined by the number of poles).

Polyphase Motor: Two- or three-phase induction motors have their windings, one for each phase, evenly divided by the same number of electrical degrees. Reversal of the two-phase motor is accomplished by reversing the current through either winding. Reversal of a three-phase motor is accomplished by interchanging any two of its connections to the line. Polyphase motors are used where a polyphase (three-phase) power supply is available and is limited primarily to industrial applications. Starting and reversing torque characteristics of polyphase motors are exceptionally good. This is due to the fact that the different windings are identical and, unlike the capacitor motor, the currents are balanced. They have an ideal phase relation, which results in a true rotating field over the full range of operation from locked rotor to full speed.

Position Error: Position error is the difference between the theoretically correct shaft position and its position as indicated by the encoder cycle count.

Power: 1. The rate at which work is done. In motion control, power is equal to torque multiplied by speed. 2.The rate of doing work or expending energy. It may be written as: Power (watts) = force x distance/time.

Power Code: Identifies the type of power supply providing power to a DC motor. Frequency, voltage, and type of rectifier configuration.

Power Factor : A measurement of the time phase difference between the voltage and current in an AC circuit. It is represented by the cosine of the angle of this phase difference. For an angle of 0 degrees, the power factor is 100% and the volt/amperes of the circuit are equal to the watts (this is the ideal and an unrealistic situation). Power factor is the ratio of Real Power-KW to total KVA or the ratio of actual power (watts) to apparent power (volt amperes).

Primary Winding: The winding of a motor, transformer or other electrical device which is connected to the power source.

Protective Relay: The principal function of a relay is to protect service from interruption, or to prevent or limit damage to apparatus.PTC - Positive Temperature Coefficient : A positive temperature coefficient thermistor is used to detect and protect a motor winding from exceeding its maximum temperature rating. Resistance of the device increases with an increase in temperature.

Pull-In Torque: The maximum constant torque, which a synchronous motor will accelerate into synchronism at, rated voltage and frequency.

Pullout Torque: The maximum friction load, at a particular inertial load, that can be applied to the shaft of a synchronous motor (running at constant speed) and not cause it to lose synchronism.

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 pull-up torque is the minimum torque developed during the process of achieving rated speed.

Pulse Rate: The frequency of the step pulses applied to a step motor driver. The pulse rate, multiplied by the resolution of the motor/driver combination (in steps per revolution), yields the rotational speed in revolutions per second.

Pulse Width Modulation (PWM): 1. A PWM controller (amplifier) switches DC supply voltage on and off at fixed frequencies. The length of the on/off interval or voltage waveform is variable. 2. Pulse width modulation (PWM), describes a switch-mode (as opposed to linear) control technique used in amplifiers and drivers to control motor voltage and current. PWM offers greatly improved efficiency compared to linear techniques.

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