Isolated Signal Converter

8272-711, 8272-712

Installation and Operation Manual

General Precautions

Read this entire manual and all other publications pertaining to the work to be performed before installing, operating, or servicing this equipment. Practice all plant and safety instructions and precautions. Failure to follow instructions can cause personal injury and/or property damage.

Revisions

This publication may have been revised or updated since this copy was produced. To verify that you have the latest revision, check manual 26311 , Revision Status & Distribution Restrictions of Woodward Technical Publications, on the publications page of the Woodward website:

The latest version of most publications is available on the publications page. If your publication is not there, please contact your customer service representative to get the latest copy.

Proper Use

Any unauthorized modifications to or use of this equipment outside its specified mechanical, electrical, or other operating limits may cause personal injury and/or property damage, including damage to the equipment. Any such unauthorized modifications: (i) constitute "misuse" and/or "negligence" within the meaning of the product warranty thereby excluding warranty coverage for any resulting damage, and (ii) invalidate product certifications or listings.

Translated Publications

If the cover of this publication states "Translation of the Original Instructions" please note: The original source of this publication may have been updated since this translation was made. Be sure to check manual 26311 , Revision Status & Distribution Restrictions of Woodward Technical Publications, to verify whether this translation is up to date. Out-of-date translations are marked with . Always compare with the original for technical specifications and for proper and safe installation and operation procedures.

Description

Woodward Isolated Signal Converters are auxiliary devices used in prime-mover control to isolate and convert a control signal received from a process sensor, computer, or programmable device, changing that control signal into a signal compatible with Woodward electronic governor controls. The output of the Isolated Signal Converter is used to influence the speed or power reference of the prime mover control.

In most cases the control signals received will be 4–20 mA, although control signals such as 0–20 mA, 1–5 volts, 0–10 volts, or 0–15 volts can also be received. The unit will convert the control signal to a signal compatible with Woodward controls.

The signal converter can extend the range of the control signal by a 2:1 ratio. (A signal of 2 to 4 volts can be expanded to an output signal to the Woodward control of 1 to 5 volts.) This expansion of range allows full Woodward control over a more limited control-signal range. Working the other direction the signal converter is capable of compressing an input signal by a 50:1 ratio. This ratio makes the range adjustment in the reduced output direction much more critical than in the expanded output direction.

Although the range adjustment could accommodate a much larger signal the input control signal should not exceed 15 volts.

The signal converter provides adjustable high and low limits which can be used to limit the speed or load change controlled by the control signal input. The limits allow the connected Woodward control to lock at a low or high level should the control-signal input leave the band between the high- and low-limit settings.

An external reference feature on the signal converter lets the high and low limits follow the regulated power supplies from some controls. This feature is used on some full authority EPG and 2500 control systems which have fluctuating power supply voltages (see “Setting Up the Converter”).

High- and low-signal-select connections are available on the output of the signal converter. When a control circuit of the governor unit is connected to either the high or to the low output-select feature on the signal converter the output of the isolated signal converter will affect the governor control only when its signal is higher than the signal already on the control circuit for high select or lower than the signal already on the control circuit for the low select.

The Isolated Signal Converter is available in two models: 8272-712 which uses 90 to 150 Vdc or 88-132 Vac supply, or 8272-711 which uses 10 to 40 Vdc supply. Except for the supply voltage, the two units are identical.

The Signal Converter is enclosed in an aluminum housing. The assembly uses a Woodward conformal-coated printed circuit board with high-temperature, high quality components.

Installation

Refer to Figure 3 for mounting information. The control is designed for switch gear mounting and may be mounted in any position. Ambient temperature must be between –40 and +160 °F (–40 and +71 °C). Provide adequate ventilation for cooling and space for installation and servicing.

Control Adjustments

Outputs are controlled by four potentiometers. These potentiometers are labeled: 

 RANGE LEVEL LOW LIMIT HIGH LIMIT

RANGE determines the change in output signal for a given change in the input signal.

LEVEL sets the base output voltage that is affected by the input signal.

LOW LIMIT sets the low limit of the controlled parameter. (The signal converter will provide the minimum signal should the control-signal input drop below the limit setting.)

HIGH LIMIT sets the high limit of the controlled parameter. (The signal converter will provide the maximum signal should the control-signal input exceed the high limit setting.)

Control Selections

See “Setting Up the Converter” for connections required to various Woodward controls. See Figure 4 for a block diagram of signal converter functions. The signal converter can provide either a positive or negative output when required for applications that use a 0 to –5 or 0 to +5 voltage signal. (An example of this application is for Process Control functional mode. A voltage output of 0 to +5 will instruct the Differential-Process Import/Export Control to export power. A voltage output of 0 to –5 will instruct the Differential-Process Import/Export Control to import power. The polarity of the process or control signal input to the Signal Converter will affect the output polarity.) Reversing polarity on the output terminals will provide inverse operating signals. All wiring of the signal converter must be done in accordance with the plant wiring diagrams included in this manual.

Isolation

The switching power supply and the differential-input circuit provide isolation from circulating currents. Circulating currents normally arise when the control signal has a grounded common and a grounded power supply.

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