Working principle and starting method of slip ring motor

Working Principle of Slip Ring Motor

A slip ring motor is a rotating electrical machine whose operating principle is based on electromagnetic induction and electrodynamics.

The slip ring motor consists of two parts: the stator and the rotor. The stator is composed of several coils and an iron core, while the rotor is composed of brushes, shafts, and rotor coils. When current passes through the stator coil, a rotating magnetic field is generated in the stator. The direction and size of the rotating magnetic field depend on the structure of the stator coil and the direction and size of the current.

The rotor coil is connected to the brush, which is connected to the external power supply. When the current passes through the rotor coil, the rotor coil is in the magnetic field of the stator and is affected by the electromagnetic induction force, thus starting to rotate. As the rotor rotates, the brush also rotates with it and constantly changes the contact point of the rotor coil, so that the current can continue to pass through the rotor coil, thus making the rotor continue to rotate.

The characteristic of slip ring motor is that the brushes and coils on the rotor can rotate, so that the current wire of the rotor coil can be prevented from winding around the shaft, so that the motor can run continuously. At the same time, because the contact point between the brush and the coil is constantly changing, the direction of the current in the rotor coil can be constantly changed, thereby generating an electromotive force on the rotor, thereby offsetting the back electromotive force, so that the motor can work at a higher efficiency.

It should be noted that since there are moving parts on the rotor of the slip ring motor, regular maintenance and care are required to ensure the normal operation of the motor.

Starting method of slip ring motor

The method of starting a slip ring motor depends on its type and power rating. Here are some common methods of starting a slip ring motor:

1. Direct starting: For small slip ring motors, the direct starting method can be used, that is, the motor is directly connected to the power supply and the start and stop of the motor are controlled by the switch.

2. Star-delta starting: For small and medium-sized three-phase slip ring motors, the star-delta starting method can be used. When starting, the motor is first turned on at a low speed, using a star winding connection, and then the motor is switched from a star winding to a delta winding connection to accelerate the motor to the rated speed.

3. Transformer start: For large slip ring motors, transformer start is usually used. Transformer start will reduce the voltage and current through the transformer in the initial stage to reduce the load when the motor starts. After starting, the motor will run at rated voltage and frequency.

4. Additional starting devices: For some slip ring motors with high power or that require precise control, additional starting devices may be required, such as soft starters or frequency converters, etc. These devices can control the starting current and acceleration of the motor to reduce the load and damage during starting.

Regardless of the starting method, attention should be paid to the safety of the motor and its surroundings to avoid accidents or damage when the motor is started. At the same time, the motor should be accelerated gradually when starting to avoid excessive load at the initial stage.