Electrical connections
Refer to the control wiring diagram in this manual for wiring details.
All shielded cable must be twisted conductor pairs. Do not attempt to tin the braided shield.
All analog signal lines should be shielded to prevent picking up stray signals from adjacent
equipment. Connect the shields to the point specified on the control wiring diagram. Wire
exposed beyond the shield should be as short as possible, not exceeding 50 mm (2 inches).
The other end of the shields MUST be left open and insulated from any other conductor. If
both ends of a shield are connected, the result may be worse than if the shield is not used.
DO NOT run shielded signal wires along with other wires carrying high voltage or high
current. See Woodward application note 50532,
Interference Control in Electronic
Governing Systems
, for more information.
Power Requirement
The 721 control requires the following power supply input voltages, with 18 watts as the
nominal power consumption at rated voltage:
• 18-40 Vdc (24 Vdc or 32 Vdc nominal)
Discrete input voltages provide on/off command signals (like RUN/STOP or IDLE/START) to
the electronic control. Each discrete input requires 10 mA at its 24 Vdc nominal voltage
rating (for 24 volt switching logic).
CAUTION
To prevent damage to the control, do not power this control from any
sources with an output voltage exceeding 41 Vdc.
Run the power leads directly from the power source to the control.
DO NOT POWER OTHER DEVICES WITH LEADS COMMON TO THE CONTROL.
Do NOT turn off control power as part of a normal shutdown procedure. Leave the control
powered except for service of the system and extended periods of disuse. Use the “Close to
Run, Open to Shutdown” contact in the control wiring diagram to shut down the engine
normally.
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