Slip Ring Induction Motor Rotor Current

In a version of the ac induction motor referred to as a wound rotor motor slip rings are used not for transferring power but for inserting resistance into the rotor windings.

Slip ring induction motor rotor current.

The motor which employing the wound rotor is known as a slip ring induction motor or phase wound motor. A wound rotor induction motor has a stator like a squirrel cage induction motor but a rotor with insulated windings brought out via slip rings and brushes. Slip rings i m provides some advantages like provides high starting torque low starting current and it improves the power factor. It is controlled by varying the rotor current of the motor.

Adjusting the resistance allows control of the speed torque characteristic of the motor. Because of various advantages like low initial current high starting torque and improved power factor it is used in applications that require high torque cranes and elevators. The slip ring induction motor has two distinctly separate parts one is the stator and other is the rotor. Wound type rotor or slip ring type rotor this type of rotor is also made up of laminated cold rolled grain oriented silicon steel to reduce eddy current loss and hysteresis loss.

However no power is applied to the slip rings. The stator circuit is rated as same in the squirrel cage motor but the rotor is rated in frame voltage or short circuit current. Definition of slip ring motor. The function of a three phase slip ring induction motor is shown in the figure below.

A wound rotor motor uses three slip rings typically made of copper or a copper alloy mounted to but insulated from the motor shaft. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below. To achieve this the rotor ac current is converted by means of a three phase. As a slip ring induction motor starts the external resistance value is increased fig 11.

As rotor current is directly proportional to the speed and torque of three phase ring type. By the uses of slip ring in an induction motor we can easily control the speed of induction motor by adding an external resistance to the rotor. It consists laminated cylindrical core which has a semi closed slot at the outer periphery and carries three phase insulated winding. The rotor winding is distributed as well short pitched to get a sinusoidal emf output.

Slip ring induction motor is one of the types of 3 phase induction motor and is a wound rotor motor type.