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Manual 55008
The Woodward centering box is used to center the magnet in the actuator
transducer relative to the control land of the pilot valve plunger. When the
magnet is centered with respect to the transducer coils, the control land of the
pilot valve plunger is also centered with the control port in the pilot valve bushing.
This centering box is used to center the proportional type of electric-hydraulic
actuator on a test stand. If the proper relationship of the magnet to the pilot valve
plunger control land is not correct, the speed of the prime mover may drift and be
slow to recover from load changes.
Equipment Provided by Woodward
Centering Box
Connector Cable
The centering box contains all of the parts required for the setting of the pilot
valve plunger to the center of the actuator control port. These parts are:
Digital Current Meter
Current Supply
Power Supply for the Centering Box
Control Switches
The discussion of each part follows with each part shown in Figure 2 or 3.
Digital Current Meter
The digital current meter is connected for reading the current being supplied to
the actuator. This meter is auto-ranging and can read a current greater than the
maximum current of the current supply. On the low range of the meter, the
current is read out to one tenth of a ma and on the high range to one ma.
Current Supply
The current supply on the centering box is a constant current source set up to be
controlled by the two adjustments on the front panel and a fixed reference. The
current supply is designed to deliver current into the 35 ohm coil resistance of the
actuator transducer. The supply consists of the current adjust circuit, current
control amplifier and the current driver shown in Figure 2. The supply uses the
115 Vac input and the voltages from the power supply to generate the currents
required for setting up an actuator. The fixed reference causes the current supply
to deliver 400 mA to the actuator coils when the current select and center normal
switches are in the center position.
Woodward
Actuator Centering Box
Tool Number 94911
Introduction
General Description
Actuator Centering Box
1
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