Every pump must be connected to two contactors (K1/K2 and K3/K4) with a mechanical interlock. Thermal relays or other motor protection devices must be

applied according to local regulation and/or individual demands.

•

RELAY 1 (R1) and RELAY 2 (R2) are the built-in relays in the frequency converter.

•

When all relays are de-energized, the first built in relay to be energized will cut in the contactor corresponding to the pump controlled by the relay. E.g.

RELAY 1 cuts in contactor K1, which becomes the lead pump.

•

K1 blocks for K2 via the mechanical interlock preventing mains to be connected to the output of the frequency converter (via K1).

•

Auxiliary break contact on K1 prevents K3 to cut in.

•

RELAY 2 controls contactor K4 for on/off control of the fixed speed pump.

•

At alternation both relays de-energizes and now RELAY 2 will be energized as the first relay.

102

AF-600 FP Design Guide

Table of Contents