LEESON NEMA 4X SCR Control: 174903.00 (Obsolete) - Manual (Page 13)

The Common of the SPDT switch is connected to
control pot HI and is switched between Speedpot
Hi and the Inhibit pin (P2). To inhibit (stop motor),
speedpot HI is closed to the Inhibit pin. To restart,
the switch is returned to Speedpot Hi. NOTE: The
control will stop fast and soft start through a fixed
acceleration range.
Two pot operation is done using two 10K
ohm speed potentiometers in parallel (both
HI's to P1-3, both LO's to P1-1). The
WIPER is switched using a SPDT switch.
TWO SPEED OPERATION
A DPDT switch is used to inhibit the control and to connect the
DBR. Typical values for the DBR (dynamic brake resistor) are 5
ohms for 120V, 10 ohms for 240V (both 35W to 50W). Note that
motor horsepower, inertia, and cycle time effect sizing of the DBR.
NOTE: This modification cannot be used with the -17B option.
DYNAMIC BRAKING
The customer supplied SPST switch is connected
in series between the speedpot HI (P1-3) and the
Inhibit pin (P2). To inhibit, speedpot HI is closed to
the Inhibit pin. To restart, the switch is returned to
open. NOTE: The control will stop and start fast,
accel is bypassed.
INHIBIT (USED INDEPENDENTLY) INHIBIT (USED WITH SPEEDPOT)
-2
-1
-3
P1
SPST
SPEEDPOT
INHIBIT
(P2)
WIPER
LO
HI
-2
-1
-3
P1
SPDT
SPEEDPOT
WIPER
LO
HI
Improves speed regulation to ±1/2% of base speed. Contol
goes to full output when input goes to zero, above and
beyond MAX trimpot setting
TACHOMETER FEEDBACK
Allows control output to follow tachometer voltage.
TACHOMETER FOLLOWER
-2
-1
P1
W
LO
HI
MOTOR
DYNAMIC
BRAKE
RESISTOR
-2
-1
-3
W
HI
LO
W
HI
LO P1
HI
SPDT
TWO 10K SPEEDPOTS
TACHOMETER
P2 INHIBIT
P1-4 -ARM
+
-
6 VDC at BASE SPEED (3 VDC at
1000 RPM for 1800 RPM MOTOR)
TACHOMETER
P1-2 POT WIPER
P1-1 POT LO
+
-
12 VDC at FULL SPEED
NOTE: NEED 1% OR LESS - TACH OUTPUT RIPPLE
NOTE: Permits starting and stopping of motor without breaking AC lines. In the event of SCR failure or false
triggering, the Inhibit circuit will not stop motor.
-4
DPDT
-3
P2
INHIBIT
INHIBIT
(P2)
-5
CONTROL MODIFICATIONS
12