Momentary Fast-Slow-Off Start-Stop Circuit - Honeywell AUTOMATIC CONTROL SI Edition Engineering Manual

ELECTRIC CONTROL FUNDAMENTALS
MOMENTARY FAST-SLOW-OFF
START-STOP CIRCUIT
Figure 37 illustrates a momentary, two-speed, start-stop
circuit with separate windings for fast and slow motor speeds.
Pressing the FAST button closes a circuit energizing starter
solenoid F for the fast windings. Pressing the SLOW button
closes a circuit energizing starter solenoid S for the slow
windings. The holding circuits and the push-button contacts
are mechanically interlocked to prevent energizing both sets of
FUSED
DISCONNECT
L1
L2
L3
TRANSFORMER
STARTER
S
F
F
F
S
F
F
S
F
F
FAST
STOP
SLOW
Fig. 37. Momentary Fast-Slow-Off Start-Stop Circuit.
windings at the same time. Pressing the STOP button opens
both holding circuits and stops the motor.
Where a mechanical interlock does not exist between the
holding circuits and push-button contacts, the fast speed start
circuit must be opened before energizing the slow speed circuit
because of the N.C. slow auxiliary contact wired in series with
the fast speed solenoid. A similar situation exists when changing
from slow to fast.
OL
T1
OL
T4
F
OL
T3
F
OL
T5
OL
T2
OL
T6
F S OL
F
(FAST AND SLOW
OVERLOADS IN
SERIES)
S
F
S
ENGINEERING MANUAL OF AUTOMATIC CONTROL
116
T4
T1
MOTOR
T3
WINDINGS
T2
T5
T6
C2540