Curtis 1204 Manual page 24

PM motor
Fig. 16
wiring to provide
freewheeling, using
4 × SPST contactors.
Although this
configuration is widely
used, we do not
recommend it.
Preferred PM
Fig. 17
motor wiring to allow
freewheeling, using
2 × SPDT direction
contactors with a third
contactor (SPST).
A resistor can be added
across the third
contactor to provide
dynamic braking
instead of freewheeling.
Curtis PMC 1204/1205 Manual
violent the effect of the sudden braking will be. If violent braking is not
acceptable for your application, use one of the wiring schemes described
below to allow the motor to freewheel in neutral or whenever the pedal is
released. However, note that sudden braking will still occur if the
opposite direction is selected and the pedal is re-applied while the
vehicle is still moving.
A partial solution is to arrange four single-pole, single-throw (4×SPST)
contactors to open the motor circuit whenever the pedal is released. This
arrangement, shown in Figure 16, causes the vehicle to freewheel in
neutral or whenever the pedal is released. The drawback to this scheme is
that if one of the contactors sticks closed, the controller's output is
shorted and the controller may be damaged. For this reason, we do not
recommend the 4×SPST arrangement — although it is widely used.
(See Fig. 15 for overall wiring)
F R
PM
F
R
POWER WIRING
A better approach — and the one we recommend — is shown in
Figure 17. The motor is reversed by the two single-pole, double-throw
(2×SPDT) contactors. A third contactor (SPST) opens the motor circuit
in neutral or when the pedal is released, allowing the motor to freewheel.
DYNAMIC BRAKING
RESISTOR (optional)
FREEWHEEL or DB
F
R
PM
F R
M-
POWER WIRING
controller B+
M- -
(See Fig. 15
for overall wiring)
controller B+
-
+
F R
CONTROL WIRING
+
F R
CONTROL WIRING
WIRING
18