KB Electronics KBMM-225D - Manual (Page 29)

WARNING! Do not disconnect and reconnect the motor armature with the AC line applied or cata-
strophic failure will result. See Section 13.2.
13.2 Armature Switching and Dynamic
Braking – If the armature is to be dis-
connected and reconnected with the AC
power applied, wire a relay (or contactor)
and a brake resistor (RB) in the armature
circuit. The Inhibit Circuit must be simul-
taneously activated when braking. Wire a
double pole double throw (DPDT)
mechanically ganged switch to the Inhibit
Terminals and the relay (or contactor)
coil, as shown in Figure 20. The resist-
ance and wattage of RB must be chosen
according to braking requirements.
When the switch is in the “Brake” posi-
tion, the relay is deenergized and allows
the motor voltage, via the N.C. contact, to be dissipated through RB and dynamically brake the motor.
Simultaneously, the Inhibit is activated and the control output is electronically “extinguished”, which elimi-
nates arcing.
When the switch is in the “Run” position, the N.C. contact opens, the N. O. contact closes, the Inhibit is
deactivated, and the motor begins to accelerate (according to the setting of the ACCEL Trimpot) to the Main
Speed Potentiometer setting.
WARNING! The Inhibit Circuit (Terminals “I1” and “I2”) is never to be used as a Safety
Disconnect since it is not fail-safe. Use only the AC line for this purpose.
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!
-
M
+
RB
Speed Control
Armature
N.O.
N.C.
Contactor Coil
AC Line Input
L1
L2
A+
A-
Motor
Relay or
Mechanically Ganged Switch
Double Pole Double Throw
I1 I2
Run
Brake
Run
Brake
FIGURE 20 – TYPICAL DYNAMIC BRAKE CIRCUIT CONNECTION