STAR TRIANGLE MATCH

This type of starting consists of supplying the motor with a reduced voltage through the connections in the motor wires. Power is supplied via a single voltage and the key makes connections to the motor terminals, reducing the starting current during starting. After a stipulated time and adjusted on the switch, the nominal voltage comes into effect. This switch provides a reduction in starting current of approximately 33% of its direct starting value. It is used almost exclusively for starting machines at no load (without load) and is suitable for machines with starting torque up to 1/3 of the nominal torque. 

The load's resistant torque must not exceed the motor's starting torque, nor must the current at the moment of commutation reach very high values. The high resistant torque causes the motor to accelerate up to 85% of the nominal rotation during star starting, when commutation occurs. At this point, the current, which was approximately equal to the nominal, goes to 320%, which does not bring any advantage, as at the start the current was 190%. 

In star connection, the motor accelerates up to 95% of the nominal speed and at this point the current is at 50%. Then switching occurs and the current rises to 170%, that is, practically equal to the star starting current. Engine speed generally stabilizes between 75% and 85% of rated speed. The transition from the star connection (highest voltage) to the delta connection (service voltage) is controlled by a timer installed in the switch, which works with a delay of 30 to 100 ms (thousandths of seconds) in order to avoid a short circuit. between phases, as the contactors cannot be closed simultaneously.