3 Point starter

Hello guys, Today we are discussing 3 point starter in brief, including the overview, construction, working, advantage, disadvantages, conclusion, etc.

The 3-point starter is an electrical device used for the motor starting. It operates in automatic and manually in both condition with also provide safety features like fault, overload condition, etc.

3-Point Starters:-

It is an electrical device used in starting condition of the motor. Basically is manually operated to reduce the starting current in the motor winding. I have connected the resistance in series that help controlling the power supply directly connected to the motor terminal. When the motor starts the rotation then we can increase the power supply then the motor reaches full speed in rotation. this is used for both domestic and industrial commercial purposes in the market.

3 point starter circuit diagram

3 Point Starters Diagram

Construction:-

The 3-point starter is basically very simplistic in the construction purpose because the whole construction can be divided into the three parts as mentioned below:-

  1.  (L) Line Terminal (Connected directly to positive supply).
  2. (A) Armature Terminal (Connected to the windings). 
  3. (F) Field Terminal (Connected to the field windings).

The handle moves sequence-wise to shift towards the run direction in with decreases the series-connected resistance. In the last position, the lever is attached to the electromagnet magnetic coil for the holding position. The lever is also connected to the spring through the sense of the overload current in the motor. when OLR (Over Load Relay) senses the overcurrent it trips the supply by using the cut of the collection of the electromagnetic relay.

Working of the 3-point starters:-

When the handle moves toward the stud attract the holding coils. the supply started to flow through the resistance in series in motor windings and the motor started the rotate. then we can change the handle position connected with another resistance the motor speed increase. So sequential manual change till the final position of the handle.

In the final position of the handle, no resistance directly supplies flow toward the motor windings. So the motor rotated at the full speed.

In a condition of overload, high current flow in the windings of the motor is sensed by the overload relay mount in a 3-point stater. if any unwanted current is sensed by the coil, the No volt coil (NVC) de-energized immediately, and the handle reaches the initial position by using a force spring. then no supply flow inside the motor. No Volt Coil or Under Voltage is basically for the protection of the under voltage electrical supply inside the machine and also prevented unwanted electrical threats.

 

three point starter construction drawbacks limitation disadvantages

Advantages of the 3-Point starter:-

  • Provide safety from the overload current
  • It has safety features to protect from the high initial starting current.
  • Low cost with minimum space required.
  • Easy to operate.

Disadvantages of 3-Point starter:-

  • In having considerable variation of power flowing through it by field rheostat.
  • This starter is not suitable for the large field current.
  • for increase, the speed from above rated speed required field resistance increase with decreased field current.

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