Electric motor heat protection circuit - has temp.-sensitive switch in series with electronic relay forming part of parallel circuit including switch contact

摘要

The circuit consists of a p.t.c. resistor in series with a Schmidt switching stage and a current sensitive switching element connected to a control voltage source. A parallel circuit consisting of a self-holding contact of the switch and a break contact of an electronic relay, is inserted between the p.t.c. resistor and the switching stage. The relay is connected to the control voltage source in series with a temp. -sensitive switch which becomes conducting below a predetermined temperature of the plant. It breaks the circuit above this temp.