Section 8 Pwrcell Ats; Contactor Switching Mechanisms; Basic V-Type Contactor - Generac Power Systems PWRcell Reference Manual

PWRcell ATS
Section 8

Contactor Switching Mechanisms

The switching mechanism is physically responsible for
carrying the rated electrical current and shifting the
connection from one power source to another.
Contactors are constructed as a double-throw switch
where a single operator opens one set of power contacts
while closing a second set. In an open transition design,
a mechanical interlock is often employed to prevent
simultaneous closure of both contact sets.

Basic V-Type Contactor

The V-Type Contactor is available in 100 through 200
Amp ratings at 250 volts maximum with a 2-pole configu-
ration (single phase only).
See and
Figure 8-1 Figure
consists of a pair of movable LOAD contacts, a pair of
stationary UTILITY contacts, and a pair of stationary
STANDBY contacts. The LOAD contacts connect to the
UTILITY contacts by energizing a utility closing coil or to
the STANDBY contacts energizing the standby closing
coil. In addition, the LOAD contacts can be actuated to
either the UTILITY or STANDBY position by means of a
manual transfer handle. The closing coils actuate and
energize using source voltage from the side to which the
load is being transferred. For example, if the contactor is
in the UTILITY position, the standby closing coil will ener-
gize utilizing generator voltage.
STANDBY
LOAD
Figure 8-1. Load Connected to Utility Power Source
STANDBY
LOAD
Figure 8-2. Load Connected to Standby Power
Diagnostic Repair Manual
8-2. A basic 2-pole contactor
UTILITY
UTILITY
Source
Utility Closing Coil C1
See Figure 8-3. The utility closing coil (C1) utilizes recti-
fied Utility source power to actuate the LOAD contacts to
the UTILITY position. When energized, the coil will move
the LOAD contacts to an "over center" position.
A limit switch opens the circuit and the spring force will
complete the transfer back to UTILITY. The bridge
rectifier, which changes the Utility source, alternating
current (minimum of 190 VAC), to direct current (DC), is
sealed in the coil wrappings. If either the coil or the bridge
rectifier replacement becomes necessary, replace the
coil assembly.
A
B
C
D
E
F
Figure 8-3. The "V-Type" Transfer Mechanism
A. Utility Closing Coil C1
B. Bridge Rectifier
C. Limit Switch XA1
Standby Closing Coil C2
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The standby closing coil (C2) utilizes rectified standby
source power (minimum of 190 VAC) to actuate the load
contacts to their STANDBY position. Energizing the coil
moves the load contacts to an over-center position. A
limit switch opens the circuit and spring force completes
the transfer to STANDBY. If replacement of either the coil
or the bridge rectifier becomes necessary, replace the
coil assembly.
Limit Switches XA1 And XB1
Movement of the LOAD contacts mechanically actuates
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the limit switches. When the LOAD contacts connect to
the UTILITY contacts, limit switch (XA1) opens the Utility
circuit to C1 and limit switch (XB1) closes the standby

Section 8 PWRcell ATS

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D. Limit Switch XB1
E. Bridge Rectifier
F. Standby Closing Coil C2
45