Direct starting of three-phase motors

 

Direct starting of three-phase motors

Manual starters are in fact disconnectors or magnetothermal circuit breakers.

They consist of a box containing one, two or three power contacts, depending on whether the power supply is single-phase or three-phase.

The box also contains a thermal protection relay, the role of which is to protect the motor against overcurrent, which can be caused by overloading the motor, and against short-circuits by fuses or a magnetic or electronic protection relay.

The starter disconnector shown in figure a) above is of the rotary handle type. Similar in appearance to a residential single-pole switch, this type of starter must be accompanied by a thermal relay to protect the motor. It can be recessed into a wall or even surface mounted.

This starter is used to control single-phase or three-phase low power motors. It is ideally suited for controlling fractional power motors operating fans, pumps, small machine tools, etc.

The manual starter with a thermal-magnetic circuit breaker, shown in figure b) above, can be used to control motors with a power ranging from 0.37 kW up to 110 kW for a maximum voltage of 690 V. It is found on machine tools (drills, lathes, woodworking machines, etc.), pumps, fans, etc. It has three power contacts, which makes it suitable for controlling three-phase motors. A thermal and magnetic relay also protects the motor.

Connection:

The following figure shows the connection diagram of a manual starter for three-phase supply.

The power source is connected to the starter at the points identified by the letter "L"; the engine is connected to the starter at the points identified by the letter "T".

 

Direct starting of three-phase motors

Manual starters are in fact disconnectors or magnetothermal circuit breakers.

They consist of a box containing one, two or three power contacts, depending on whether the power supply is single-phase or three-phase.

The box also contains a thermal protection relay, the role of which is to protect the motor against overcurrent, which can be caused by overloading the motor, and against short-circuits by fuses or a magnetic or electronic protection relay.

The starter disconnector shown in figure a) above is of the rotary handle type. Similar in appearance to a residential single-pole switch, this type of starter must be accompanied by a thermal relay to protect the motor. It can be recessed into a wall or even surface mounted.

This starter is used to control single-phase or three-phase low power motors. It is ideally suited for controlling fractional power motors operating fans, pumps, small machine tools, etc.

The manual starter with a thermal-magnetic circuit breaker, shown in figure b) above, can be used to control motors with a power ranging from 0.37 kW up to 110 kW for a maximum voltage of 690 V. It is found on machine tools (drills, lathes, woodworking machines, etc.), pumps, fans, etc. It has three power contacts, which makes it suitable for controlling three-phase motors. A thermal and magnetic relay also protects the motor.

Connection:

The following figure shows the connection diagram of a manual starter for three-phase supply.

The power source is connected to the starter at the points identified by the letter "L"; the engine is connected to the starter at the points identified by the letter "T".