User manual

55 of 148
3.5 Speed Sensing
The speed sensing menu allows you to select the source to use for sensing the
rotational speed of the engine. There are three options to choose from:
1. J1939 Input – If the engine/generator comes equipped with an engine
control module (ECM) that supports the J1939 protocol then the GSC400
can obtain the engine speed from the ECM.
2. Magnetic Pickup – If the engine/generator is equipped with a magnetic
pickup sensor then the sensor can be connected to the SPEED 1 and
SPEED 2 spade terminals on the GSC400.
3. Generator Output – The GSC400 can also determine the engine speed
indirectly from the generator frequency. The voltage source of the
generator must be connected to the SPEED 1 and SPEED 2 terminals.
Over-speed warnings and failures as well as under-speed warnings and
failures can be set from the menu in units of RPM. The warnings and failures
apply to all three options above.
3.5.1 Rated Speed
The rated speed is the speed (in revolutions per minute, RPM) the engine runs
at when producing power. For example some generators run at 1800RPM while
others run at 3600RPM.
3.5.2 Rated Frequency
If using Generator Output:
The rated frequency is the frequency of the generator (usually either 50Hz or
60Hz).
If using magnetic pickup:
For a magnetic input the rated frequency is determined by the number of teeth on
the flywheel and is calculated by:
Rated frequency (Hz) = (Number of teeth x Rated Speed) / 60
Where:
Number of teeth – number of teeth on the flywheel the magnetic pickup
sensor is attached.
Rated Speed – the speed at which the generator produces power in RPM
(revolutions per minute).