Motor control circuits
Direct-On-Line Starting Circuit with Protection and Indicator Lamps
What is DOL starting with protection and indicator lamps?
It is a direct-on-line starter with a phase monitoring relay and indicator lamps added. The phase monitoring relay detects supply faults such as phase loss and wrong phase sequence; the indicator lamps on the panel door show that the motor is running and which fault has occurred.
Where is it used?
It is used in pump, fan, compressor and conveyor panels, especially in rural areas and on weak supplies. Phase loss is one of the most common reasons three-phase motors burn out; the phase monitoring relay stops the motor in that case. The indicator lamps also shorten troubleshooting time.
Power circuit and control circuit
The power circuit has the circuit breaker, contactor, overload relay and motor, plus the measuring terminals of the phase monitoring relay. The control circuit uses the phase monitoring relay's contacts, the overload relay's normally open and normally closed contacts and indicator lamps of different colours. It is a good example of how the two contacts of an overload relay are used separately.
What to watch out for
The phase monitoring relay's voltage and delay settings are made for the supply. Indicator lamp colours follow the standards: usually green for running, red for fault and amber for warning.
Parts used
- Motor 3~
- M1
- Indicator lamp
- H1, H2, H3
Run it in the simulator.
This circuit is ready in the CoilPath library. Open it, press the buttons and follow the current. It also comes with a wiring view and a panel layout.