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Murphy - Keystart 9620 series installation instructions 00-02-0657 revision A 22
nd
September 2008 p4/4
Keystart model 9621 includes a speed sensing input and automatic
shutdown protection for engine overspeed faults. Before use, model
9621’s speed input must be correctly configured (using circuit-board
links J2 and J3) and calibrated (using potentiometers VR2 and VR3).
Selection of speed signal source: links J2 and J3
Links J2 and J3 allow configuration of the speed sensing input
(terminals 13 and 14) for either generator AC (the factory default
setting) or magnetic pickup signals. Use small pliers to add or
remove the links as required:
J2 and J3
links
Terminal 13 and 14 configuration
ON Generator AC, 70 - 270 VAC rms, 50 or 60 Hz nominal.
OFF Magnetic pickup, 10 – 60 VAC peak, 2000 to 6500 Hz
nominal.
Speed calibration
Speed calibration is a two stage process:
1) Nominal speed calibration: potentiometer VR2
The factory default setting is for generator AC speed sensing, with
standard models for 50 or 60Hz nominal calibration. To recalibrate
for other systems:
• Select the speed sensing method (generator AC or magnetic
pickup) using links J2 and J3 as detailed above.
• Turn VR2 fully clockwise (sets calibration for maximum nominal
frequency).
• Connect a 0 – 1mA, 75 Ohm meter between pin 11 and battery
negative, as detailed in ‘electrical connection’ above.
• Start and run the engine to nominal (normal running) speed.
• Turn VR2 anti-clockwise (decreasing the calibration frequency)
until the ammeter rises to read 0.75mA.
2) Overspeed setting: potentiometer VR3
VR3 allows adjustment of the overspeed trip point, between
approximately 100 and 130% of the nominal AC or magnetic pickup
frequency (as set using VR2). The VR3 factory default setting is
110% (of either 50 or 60Hz). To adjust the overspeed trip level:
• Turn VR3 fully clockwise (to maximum, approx. 130% of nominal)
• Start and run the engine. Increase engine speed to the required
overspeed/over-frequency trip level.
• Turn VR3 slowly anti-clockwise (decreasing the overspeed trip
level) until the Keystart shuts down the engine and indicates
‘overspeed’.
Where the engine speed cannot be22 September 2008 adjusted,
or if the speed signal cannot be simulated (e.g. with an adjustable
signal generator), an approximate overspeed setting must be made
(e.g. potentiometer mid-span = approximately 115% of VR2 nominal).
Maintenance and Warranty
The Keystart series contains no user-serviceable parts. Maintenance
is therefore limited to the following preventative checks:
• Check that all electrical connections are secure.
• Check that the Keystart is securely clamped in the front of
panel aperture, and kept free from ingress of water or build
up of excessive dust/dirt. The front face label and casing may
be wiped with a clean, damp cloth. Do not use cleaning solvents.
Each Keystart is supplied with a two year warranty on materials
and workmanship. In the event of a fault or technical query, please
contact your Murphy representative for technical support.
SPEED SENSING AND CALIBRATION
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E-mail: sales@fwmurphy.com
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textual matter and illustrations, is copyright protected by Frank W Murphy Ltd., with all rights reserved. © 2008 Frank W Murphy Ltd.