SA-CSIR MS402 0.55kW 1×200-240V/50Hz

Grundfos SA-CSIR 0.55kW control box for use with 0.55kW Single Phase SP series borehole pumps.

SP Series MS402 motors have 2 sets of windings, the larger main winding and an auxiliary winding. The control box contains a capacitor and a relay, upon startup the relay holds the starting capacitor in circuit which creates an electrical phase shift. This phase shift provides extra torque until the motor spins quickly enough to overcome the inertia applied to the motor by the mass of the impeller stack and the reluctance of water flow. Once the motor is turning quickly enough the extra torque is no longer required and the start capacitor is removed from the circuit by the relay and the pump runs on the main winding.

Some of the larger single phase SP pumps also require a run capacitor, this is an additional capacitor which once the pump has started using the start capacitor, the start capacitor is taken out of circuit by the relay and at the same time the run capacitor is put into circuit. The pump then uses both the main and auxiliary windings to run using the run capacitor.