User guide

Glossary-2
inertial load - A load (such as flywheel or fan) that tends to cause the motor shaft to
continue to rotate after power has been removed (stored kinetic energy). If this
continued rotation cannot be tolerated, some mechanical or electrical braking means
must be applied. This application might require a special motor due to the energy
required to accelerate the inertia. Inertia is measured in either lb-ft
2
or oz-in
2
.
input parameter - You can change the value of the parameter through the
OIM
.
LCD - Liquid Crystal Display.
LED - Light Emitting Diode.
motor - A device that converts electrical energy to mechanical energy to turn a shaft.
motor electrical time constant - The ratio of electrical inductance (L
a
) to armature
resistance (R
a
).
motor identification -
• Frame designation (actual frame size in which the motor is built)
• Horsepower, speed, design and enclosure
• Voltage, frequency and number of phases of power supply
• Class of insulation and time rating
•Application
motor nameplate - The plate on the outside of a motor that describes the motor,
HP
,
voltage,
RPM
, efficiency, design, enclosure, etc.
motor thermostat - Unit applied directly to the motor’s windings that senses winding
temperature and might automatically break the circuit in an overheating situation.
non-retentive - Changes to the parameter value are not saved when power is
removed.
output parameter - Provides output information. Value cannot be changed through
the
OIM
.
power (P) in kW - The measure of the rate of work. One kilowatt (kW) is equivalent to
lifting 98 kg to a height of one meter in one second. The kW rating of a motor is
expressed as a function of torque and
RPM
. For motors, you can use this approximate
formula:
where:
• P = horsepower
• T= Torque (in Nm)
• RPM = revolutions per minute
Inertia Reflected to the Shaft of the Motor Load Inertia
Load RPM
Motor RPM
------------------------------


2
×=
PT
RPM
9550
-------------×=