Product Manual

PMAC (Permanent Magnet AC): Motors that use magnets imbedded
in the rotors and is a synchronous motor, meaning that the rotor spins
at the same speed as the motor’s internal rotating magnetic field. This
offers greater efficiency and better dynamic performance.
Polarity: As applied to electric circuits, polarity indicates which terminal
is positive and which is negative. As applied to magnets, it indicates
which pole is north and which pole is south.
Poles: Magnetic devices set up inside the motor by the placement and
connection of the windings. Divide the number of poles into 7200 to
determine the motor’s normal speed. For example, 7200 divided by 2
poles equals 3600 RPM.
Power Factor: The ratio of “apparent power” (expressed in kVA) and
true or “real power” (expressed in kW).
Power Factor =
Real Power
Apparent Power
Apparent power is calculated by a formula involving the “real power,”
that which is supplied by the power system to actually turn the motor,
and “reactive power,” which is used strictly to develop a magnetic field
within the motor. Electric utilities prefer power factors as close to 100% as
possible, and sometimes charge penalties for power factors below
90%. Power factor is often improved or “corrected” using capacitors.
Power factor does not necessarily relate to motor efficiency, but is a
component of total energy consumption.
Prime Mover: In industry, the prime mover is most often an electric
motor. Occasionally engines, hydraulic or air motors are used. Special
application considerations are called for when other than an electric
motor is the prime mover.
Pull Out Torque: Also called breakdown torque or maximum torque,
this is the maximum torque a motor can deliver without stalling.
Pull Up Torque: The minimum torque delivered by a motor between
zero and the rated RPM, equal to the maximum load a motor can
accelerate to rated RPM.
Pulse Width Modulation: Abbreviated PWM, the most common
frequency synthesizing system in AC drives; also used in some DC drives
for voltage control.
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