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What is the purpose of the holding contact across the Start button in a DOL motor starting circuit?

What is the purpose of the holding contact across the Start button in a DOL motor starting circuit?

Below given contactor is of 4-pole type. It contains three NO (normally open) contacts that connect the motor to supply lines, and the fourth contact is “hold on contact” (auxiliary contact) which energizes the contactor coil after the start button is released.

How many contacts are used in DOL starter?

The three NO contacts are used to connect the induction motor to supply lines whereas the auxiliary contact is used to boost the contactor coil when the start button is opened. If any error takes place, then holds on contactor gets deactivated.

What is DOL circuit?

The Direct On Line Motor Starter (DOL) consist a MCCB or Circuit Breaker, Contactor and an overload relay for protection. Electromagnetic contactor which can be opened by the thermal overload relay under fault conditions.

What is the function of a holding circuit?

The main function of a sample-and-hold (S/H) circuit is to take samples of its input signal and hold these samples in its output for some period of time.

How do you wire a 3 phase DOL starter?

Three Phase DOL Starter Wiring Diagram:

  1. L1 is connected to the R phase through MCCB.
  2. L2 is connected to the Y phase through MCCB.
  3. L3 is connected to the B phase through MCCB.
  4. Point 1 is connected to R-phase while point-2 is connected to overload relay T1 point.

How do you control a DOL starter?

The DOL Starter is started by simply pressing the Start Push button and stopped by pressing Stop push button. This method has easy way of controlling the device. If the push button is pressed, the contactor gets energised and gets closed.

What is the purpose of holding contact?

The holding contact in the relay circuit are used to provide the current path to the relay coil as the start button is released. The holding contact is in parallel with the start and in the same way the stop wire is in series to break the relay circuit and then stop the motor.

What is holding circuit?

The holding circuit interlock is a normally open auxiliary contact on magnetic starters or contactors. Used in three wire control schemes with momentary inputs.

Why is DOL starter used up 5 hp?

The direct on line (DOL) starter method of an induction motor is simple and economical. In this method, the starter is connected directly to supply voltage. By this method, small motors up to 5 kW rating are started to avoid the supply voltage fluctuation.

How are holding contacts connected?