In this post, I will briefly show the star delta control diagram with timer. Use simulation software to make it easier for readers to understand the star delta starter circuit.
When do we use star delta starter circuit?
The star-delta starter circuit usually uses to reduce the starting current for medium to large-capacity motors. The starting current of the large motor will affect the power supply and other equipment. When three phase motor starts in star mode, the starting current is less than three times compared with delta mode. When the motor speed reaches 75% of the rated speed, it will switch to delta mode
The circuit uses a timer to automatically convert the motor’s operating mode from star to delta mode. This circuit will work more accurately than manual star delta starter circuit diagram.
Star delta control circuit diagram with timer
Star delta connection with timer
The circuit diagram is drawn as pictured above. The dynamic circuit uses three contactors. The control circuit uses two push buttons to control the running and stopping of the motor.
When we press the ON button, the motor will operate in star mode. At this time, the timer starts counting time. When the timer reaches the preset time, the timer contacts will change their state, causing the circuit to go into delta mode.
When we press the OFF button, this circuit will return to its original state.
a. Star mode
When we press the ON button, the dynamic contacts of contactor K and contactor K2 are closed, and the motor starts in star mode. Timer will determine how long the motor operates in star mode. Depending on the power and rated speed of the motor, we need to adjust this time. When the motor switches to delta mode, the motor speed should reach 75% of the rated speed.
Motor is working in star mode
b. Delta mode
When Timer T counts to the preset value, the timer T contact changes state. In the dynamic circuit, the contact of contactor K and K1 is closed, which means the motor work in delta mode. In delta mode, the motor operates properly with the rated power and speed.
Motor is work in delta mode
Simulation Video about star delta control diagram with timer
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