Metron Fire Pump Controllers conform to the latest requirements of Chapter 7, National Fire Protection Association Pamphlet 20, Standard for Centrifugal Fire Pumps as adopted by Underwriters Laboratories and Factory Mutual. They are withstand rated and listed by Underwriters' Laboratories and approved by Factory Mutual Research Corporation.
Sizes range from 15 to 700 horsepower, 200 to 600 volts, 60 Hz. These controllers are for use on Reduced Voltage type installations.
Only the highest quality components, all UL listed or UL recognized, are used throughout to assure the best possible reliability. The cabinet is fabricated of heavy gauge reinforced steel with drip-proof hood. All field wiring and service connections may be made from the front, allowing the controller to be mounted flush against a wall.
The controller is completely wired, assembled, and tested at the factory before shipment, and ready for immediate installation.
Wye-Delta motors have all six leads brought out to the motor terminal box. These leads are connected by the contoller first in the Wye configuration which draws only 33% of normal starting current and develops 33% of normal starting torque. After a short time delay, the controller then connects the motor winding in a Delta configuration, applying full voltage and drawing full load running current and developing full running torque.
With the M430 open transistion types, there is a very short period of time where no voltage is applied to the motor during transition from Wye to Delta connections. This condition can cause current surges or disturbances fed back into the main power source. The magnitude of the surges is proportional to the phase difference between the voltage generated by the running motor and the power source. These transients can in some instances affect other equipment which are sensitive to current surges.
The M435 closed transition types provide a smoother transition from Wye to Delta by keeping the motor continuously energized during the transition period. This is accomplished by means of resistors which are connected in the circuit during the momentary period of transition from Wye to Delta.
Metron Wye-Delta Controllers incorporate a mechanical as well as electrical interlock to prevent the Wye connecting contactor from being energized at the same time as the Delta contactor.
An emergency start lever to close starting contactor independent of automatic control circuits. When used, this lever will bypass the reduced current start feature and start the motor with full inrush current drawn from the power source.