This hydrostatic transmission controller is designed to be used where both the pump and the motor are equipped with an electrical displacement control that is varied to obtain the required operating speed range. The output signal to the pump displacement controller is bipolar, for reversing applications.
The controller is an extremely accurate bipolar linear current amplifier. When it is operated in the open loop mode, it is capable of maintaining the preset output within 1% as the input voltage, ambient temperature and load impedance are varied over the specified range.
The controller is supplied as a single, industrial grade modular circuit board assembly. The circuit board is solder masked and conformal coated. All models include a regulated bipolar reference supply as well as the devices required to set the pump and motor null position, gain and maximum output. In addition, a phase control adjustment is included to set the motor crossover point. The motor output may be arranged to either increase or decrease the displacement control valve signal with an increase in the input command signal. Models are available to operate directly from the 115 VAC or 230 VAC power line or a bipolar 18 to 30 volt DC power supply. The output is capable of supplying a maximum of 200 ma. of current to the pump and motor displacement control valves.
A number of optional features are offered. These include linear acceleration and deceleration control, in both directions, as well as built in dither generator modules for both the pump and the motor. The dither generators are supplied with controls to set both the amplitude and frequency of the dither signal to the servovalve coils.
The controller will accept a bipolar, analog input signal to produce the required output speed and direction of rotation. This command signal can be obtained from the internal reference with a potentiometer or generated externally. Bipolar input signals of 5 or 10 volts are standard. For unidirectional applications the controller will accept and follow a 4 to 20 ma. current input. For closed loop operation, a scaling circuit with adjustable gain has been included so that commonly available analog, velocity transducers can be interfaced with a minimum of external parts.
All of the external power and signal connections are made to a single barrier type terminal block supplied with #6-32 wire clamping screws. The options and operating modes are selected with multiple position pin headers, thus the controller can be configured for a number of applications without the need to solder or remove any components.
Applications: Hydrostatic transmissions with variable pump and motor electrical displacement controllers with coil currents to 200 ma.