With mains contactor, style 3-stage, rotor 3-phase [t-head1-pg]

Function [t-head3-pg]

Pushbutton I energizes mains contactor Q11: normally open contact Q11/14–13 transfers the voltage, Q11/44–43 energizes timing relay K1. The motor is connected to the supply with rotor resistors R1 + R2 + R3 in series. When the set starting time has elapsed, normally open contact K1/15–18 energizes step contactor Q14, which short-circuits starting stage R1 and via Q14/14–13 energizes timing relay K2. When the set starting time has elapsed, K2/15–18 energizes step contactor Q12, which short-circuits starting stage R2 and via Q12/14–13 energizes timing relay K3. When the set starting time has elapsed, K3/15–18 energizes final step contactor Q13, which is maintained via Q13/14–13. Step contactors Q14 and Q12 as well as timing relays K1, K2 and K3 are de-energized via Q13. Final step contactor Q13 short-circuits the rotor slip rings: the motor operates at the rated speed.

The motor is switched off either by pushbutton 0, or in the event of an overload, by normally closed contact 95–96 of the overload relay F2 or normally open contact 13–14 of the motor-protective circuit-breaker or circuit-breaker.

Step contactor Q13 and Q12 with their resistors R3, R2 and timing relays K3, K2 are omitted in single-stage or two-stage starting circuits. The rotor is then connected to the resistance terminals U, V, W2 or U, V, W1. The references for step contactors and timing relays in the wiring diagrams are then changed from Q13, Q12 to Q12, Q11 or to Q13, Q11 as appropriate.

When there are more than three stages, the additional step contactors, timing relays and resistors have appropriate increasing designations.