
16
20 - Wheel System, Traction
Circuit Description
Drive Power
Main battery power is always present at the drive controller from the battery (fused at 30 amps), however,
the drive controller contains an internal main relay to inhibit main power when the KSI circuit is inactive
When the KSI input receives battery-positive voltage, the controller pre-charges its internal DC Bus
capacitor bank at 1 5 amps for 0 5 seconds, before it closes its own internal main relay This is referred to as
the precharge function, and is used to reduce arching at the relay contacts In short, it permits the capacitor
voltage to slowly approach battery voltage before full battery power is connected to the internal capacitors
The significance of this discussion is that if there is an unexpected drain (faulty load or short circuit) on
the DC Bus of the controller before the KSI circuit is energized, it will prevent the precharge function from
properly charging the capacitor bank, and the controller will issue a precharge error code
Throttle and Speed Limit
Both the speed limit and throttle potentiometers receive a 5-volt bias voltage from the Curtis 1228 drive
controller This results in the wiper voltages from both potentiometers to have a 0 to 5 volt range The Curtis
drive controller interprets these voltages as the machine drive commands
Brake Output (Scrub Enable)
When the drive controller is commanded to move, it activates its “brake release” function by bringing
the Brake(-) output to battery-negative voltage This results in both positive and negative voltages being
available to the various scrub circuits Previously the scrub circuits were disabled, because both sides of the
circuits were at the same battery-positive voltage, and no current could flow.
Refer to the
on page 33 for a further description of the circuits affected by the
Brake output
Speed Pot
100K Ohm
RED/GRN
YEL/BLK
B
LK
R
ED
PNK/BLU
BLU
WHT
ORN
YEL
PNK
S1
Key Switch
P1
CURTIS 1228
POT HI
3
THR POT
4
KSI
5
POT LO
13
BRAKE-
6
B+
B-
M
1
M
2
M
1
M
2
SPD POT
18
BRAKE+
14
R1
Throttle Pot
5K Ohm
R2
M
M1
MOTOR, DRIVE
-
+
36 VDC
+
-
VIO
B-
Solution Solenoid
Detergent Pump
Brush Motor Relay
Hour Meter