MOTOR CONTROLLERS
Electrical Distribution Systems
Figure 11 Magnetic Contactor Assembly
Motor Controller Types and Operation
Within the two basic categories of motor controllers, there are three major types of AC across-
the-line controllers in use today. There are low-voltage protection (LVP), low-voltage release
(LVR), and low-voltage release effect (LVRE) controllers.
The main purpose of an LVP controller is
Figure 12 LVP Controller
to de-energize the motor in a low voltage
condition and keep it from re-starting
automatically upon return of normal voltage
(Figure 12).
LVP Controller Operation:
1.
Push the START button, which
energizes contactor coil M, closing
the M and Ma contacts. When the
START button is released, the
circuit
will
remain
complete,
because the Ma contact remains
closed, shunting the open start
switch.
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