Specifications

flow from the battery can cause personal injury or property damage.
All checks, adjustments, and repairs in the drive unit compartment are done with the compartment
cover removed. Remove the drive unit compartment cover for access to the electrical components.
WARNING
The capacitor in the transistor controller can hold an electrical charge after the battery has
been disconnected. To prevent electrical shock and personal injury, discharge the capacitor
before inspection or repairing any component in the drive unit compartment. Wear safety
glasses. Make certain the battery has been disconnected. DO NOT use a screwdriver to
discharge the traction motor controller.
CAUTION
To avoid controller damage, always disconnect the battery before disconnecting any cables
from the controller. Discharge the capacitor, and never put power to the controller with any
power wire disconnected. Never short any controller terminal or motor terminal to the battery.
Make sure to use proper procedure when servicing the controller.
The following steps must be followed to discharge the capacitors before any checks or repairs are
performed on the controller or any part of the electrical system.
1. Block the wheels so that the truck will not roll or block the truck so that the wheels are off the floor.
See How to Put Lift Truck on Blocks.
2. Turn the key switch to the OFF position and disconnect the battery.
3. Discharge the capacitors in the controller by connecting a 200-ohm, 2-watt resistor across the
controller’s B+ and B− terminals using two insulated jumper wires. See Figure 1.
NOTE: DO NOT use any other method of discharging the capacitors. Remove the 200-ohm, 2-watt
resistor before reconnecting the battery.
1. POSITIVE CONNECTION
2. NEGATIVE CONNECTION
3. JUMPER WIRES
4. 200-OHM, 2-WATT RESISTOR
Figure 1. Discharging the Capacitors
Description
CURTIS PMC 1297 TRANSISTOR MOTOR CONTROLLER
The Curtis controller is a solid state DC motor controller utilizing SEM technology. It can control the
traction motor, brake, and hydraulic system. The controller receives inputs from the control handle by
serial communication, and direct inputs from other switches depending on model. These may include
the following:
• Key switch
• Control handle arm position switch
• High-speed switch
The controller directly controls the traction motor, lift pump motor, main contactor, and the brake (on
some models). The motor controller controls the speed of the traction motor and the hydraulic lift pump
motor operation. The controller software provides self diagnostics which are accessed by means of a
Curtis handset.
PRINCIPLES OF OPERATION
The Curtis 1297 SEM Traction Motor Controller uses a sophisticated microprocessor to control the
logic and operation of the controller, eliminating the need for forward and reverse contactors. The SEM
motor controller operates on the principle of controlling the motor field circuit and the motor armature
circuit independently. The controller has many programmable features, including maximum speed,
acceleration rate, neutral braking, and braking current limit. The SEM controller includes a full range of
features as well as diagnostic and setup capability for reliable operation.
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