(r-bar) is the per unit armature circuit resistance using counter
emf as a base.
The number of times per minute the shaft of the motor (machine)
rotates. This is a function of design
and the power supply.
The standard type of stator winding used in motor under 1,000
volts. The coils are random would with
round wire as opposed to flat form would coils.
WINDING RTD
A resistance device used to measure temperature change in the motor windings to detect a possible over heating condition. These detectors are embedded into the winding slot and their resistance varies with temperature.
BEARING RTD
A probe used to measure bearing temperature to detect an overheating
condition. The RTD’s resistance varies
with the temperature of the bearings.
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 reaches is peak.
Reflective waves can occur in variable-speed motor applications
when the drive and motor are place a considerable distance apart.
The combination of long lead (cable) lengths and the fast switching semiconductors
in the drive can cause voltage spikes at the motor’s terminals.
These spikes can cause the motor’s insulation to deteriorate.
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.
The characteristic of a magnetic material which resists the
flow of magnetic lines of force through it.
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 slop under load. Reluctance motors
have lower efficiencies, power factors and torque than their permanent magnet
counterparts.
The degree of obstacle presented by a material to the flow
of electric current is known as resistance and is measure to Ohms.
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 fractional horsepower motors
for fans and blowers.
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 necessary, the armature
circuit is reversed. In some cases,
it is advantageous to reverse the field connections of shunt motors, since the
controls have to handle much less current, especially on large motors, than
do armature-circuit contactors. An AC
motor is reversed by reversing the connections of one let on three-phase power
or by reversing the leads on single phase.
A special bearing system with cylindrical rollers capable of
handling belted applications too large for standard ball bearings.
The force created by the stator once power is applied to it
that causes the rotor to turn.
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 together, and act as a conductor for the induced magnetic field.
The squirrel cage is made by casting molten aluminum into the slots cut
into each lamination.