DOL Starter panel - Star-delta Starter Panel

DOL Starter panel - Star-delta Starter Panel

Direct on-Line start is probably the simplest and traditional type of start and it is to connect the motor directly to the power supply performing therefore a full-voltage start-up.It is often abbreviated with the acronym DOL.

DOL (Direct on Line) start is the simplest and most cost-effective system for starting pumps and motors and it is traditionally the most widely used. The induced current is the rotor is high. This results on a peak current on the network which can be 5 to 8 times the nominal current.

They are suitable for startup of small submersible pumps, deep well pumps or booster sets with surface pumps. DOL control panels need a direct connection to the power supply network, which implies:

  • Start at full voltage and constant frequency
  • High starting torque
  • Very short acceleration times.

Star-delta Starter Panel

Star Delta starting is the best known and perhaps the most widely used low voltage starting method. It is used to start the pump's motor with lower levels of mechanical stress and with current limitation during start-up; it does this with the aid of a timed system which switches the control contractors installed inside the panel.

Star-delta starting reduces starting current and torque to values of 33% (1/3) of those measured during direct starting. During start-up, the currents flowing through components are lower than the motor's related current.