Typical Dynamic Brake Circuit Connection - Baldor BC142 Installation And Operation Manual

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.
When the switch is in the "Brake" posi-
tion, the relay is deenergized and allows
the motor voltage, through the N.C. con-
tact, to be dissipated through RB and
dynamically brake the motor. Simultaneously, the Inhibit is activated and the control output is electronically
"extinguished", which eliminates 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 (I1, I2) is never to be used as a Safety Disconnect since it is not
!
fail-safe. Use only the AC line for this purpose.
FIGURE 20 – TYPICAL DYNAMIC BRAKE CIRCUIT CONNECTION
Speed Control
L1
AC Line Input
L2
I1
N.O.
A+
N.C.
RB
A-
I2
Double Pole Double Throw
Run
Mechanically Ganged Switch
Brake
Run
Brake Relay or
Contactor Coil
+
Motor
M
Armature
-
29