MultiTek Speed Sensing Relay
Product Code M200-ST3
Normal running speed 1800 rpm
Number of teeth on flywheel 50
Magnetic pick up output voltage 10 volt pk-pk
The M200-ST3 is most commonly used to detect the speed of engines used in generating sets. The pick-up, situated close to the flywheel, produces a high frequency pulse train directly proportional to the number of teeth passing it. The frequency is converted by the ST3 into a mA signal directly proportional to the rotational speed of the flywheel.
The relay provides the user with the following adjustments, which allows the control of start up and normal running and protects against over and under speeds of the generator.
Adjustment of crank speed 10 to 50%
Adjustment of under speed 50 to 100% Adjustment of over speed 100 to 133 %
A mA output signal proportional to input frequency.
Typical start-up as follows -
When the speed of the motor reaches the crank's set- point, the crank relay energises, disengaging the crank starter. When the under speed set-point is reached, the under speed relay is energised and the motor is now in the normal running condition with all relays energised. Should an under or over speed condition occur the appropriate relay is de-energised. Two other safety features are incorporated; if the pick-up sensor input lead breaks the over speed relay will de-energise also the crank relay will only de-energise when the input frequency goes below 20% of the set-point. The mA output signal can be fed to digital or analogue meters scaled in speed, or to provide a control signal to a PLC etc.
Pulses 5V-75V peak to peak
Frequency 1000-10000 Hz (speed of rotation
RPM x number of teeth / 60)
Open circuit protection Over-speed relay de-energised
Rated value 0-1mA = 133% of nominal speed
Load resistance < lOk Ohm
Calibration Value 0.75mA = 100% of nominal speed
Range Crank 10 to 50%
Under 50 to 100%
Over 100 to 130%
Repeatability Better than 0.5% of full span
Hysteresis 2% (under, over) crank resets at
Operating time Typically 200 ms
DC Voltage 24 VDC ±20%
WEIGHT& CASE SIZE
Approx. 0.5kg. l00mm case
NOTE: The 3 relays in this product are single pole changeover.
M200-ST3 Speed sensing relay
1. Calibration at temperature other than 23º C
2. Set-points are factory set. Specify frequency of crank; under speed and over speed settings required.