P9 ELECTRICAL WIRING-3 PHASE
6. 1 DIRECT ON LINE
Direct On Line (DOL) starting is the simplest, cheapest and most common starting method. It actually gives the
lowest temperature rise within the motor during startup of all the starting methods. But the drawback is starting
current can be 3-8 time of full load current. Therefore, it is not recommend for pump power higher than 5.5KW in
public low voltage mains 400V.
The typical common 3 phase pump Run / Stop starter is Direct-On-Line Starter that include:
1. Motor Circuit Breaker is a short circuit magnetic protection devices.
2. Control unit for Run and Stop operation and status monitoring.
3. Protection relay is an overload thermal protection device.
4. Single phase MCB for secondar y protection.
I
t is a typical wiring diagram without ground wire for reference only. All electrical rating of
individual device has to match with pump's current rating specification.
Direct-On-Line (DOL) Starter typical wiring.
DOL Starter can be applied to motor connect in Delta or WYE/Star connection.
MCB
Stop
Contactor
Run
Protection
Relay
Motor Circuit
Breaker
Low Voltage Delta Connection
High Voltage WYE/STAR Connection
