electric slipring

Slip ring motors, also known as wound rotor motors, are unique electric motors that possess distinct operating principles. Understanding how slip ring motors work is essential to comprehend their functionality and applications. This article provides a step-by-step guide to explain the working of a slip ring motor.

Explanation of Slip Ring Motor

Definition and Construction

Before delving into the working principle, it is important to understand the basic components of slip ring motors. They consist of a stator with fixed windings and a rotor with windings connected to external electrical circuits through slip rings. The stator windings generate a rotating magnetic field, while the rotor windings receive electrical energy through the slip rings.

Working Principle of Slip Ring Motor

Step 1: Power Supply to Stator Windings

The working of a slip ring motor begins with the power supply to the stator windings. When electrical power is supplied to the stator windings, they create a rotating magnetic field. This rotating magnetic field is crucial for motor operation and sets the stage for further steps.

Step 2: Initial Rotor Positioning

Initially, the rotor windings are short-circuited through the slip rings. This short-circuiting is achieved by connecting the slip rings using external resistance, typically in the form of resistors. The short-circuiting ensures that the rotor windings are energized and ready for operation.

Step 3: Starting the Motor

To start the slip ring motor, the slip rings are initially connected to the resistors, allowing a reduced voltage to reach the rotor windings. This limited voltage causes a low starting current and a relatively high starting torque. The reduced voltage helps in overcoming the inertia of the motor and initiating rotation. The high starting torque enables the slip ring motor to handle heavy loads during startup.

Step 4: Transition to Normal Operation

As the slip ring motor gains speed and stability, the external resistors are gradually removed from the rotor circuit, reducing the resistance. This transition from high resistance to low resistance allows the motor to reach its full speed and operate at normal conditions. The reduction in resistance enables the rotor windings to receive the full voltage from the power supply, ensuring optimal motor performance.

Functioning of Slip Rings and Brushes

Slip Rings

Slip rings play a crucial role in the functioning of slip ring motors. They are conductive rings mounted on the rotor shaft. The slip rings enable the transfer of electrical energy from the stationary part (stator) to the rotating part (rotor) of the motor. By maintaining continuous electrical contact, the slip rings allow the flow of electrical energy to the rotor windings, ensuring the motor’s operation.


Brushes are essential components that maintain continuous electrical contact with the slip rings. Typically made of carbon or graphite, brushes are mounted on the stationary part of the motor and make contact with the slip rings. The brushes ensure a constant connection between the stationary and rotating parts, allowing for the efficient transfer of electrical energy. They also help in reducing friction and ensuring a reliable electrical connection.

Slip ring motors work based on the principles of electromagnetic induction and external resistance. Understanding the step-by-step process of slip ring motor operation, from power supply to the stator windings to the functioning of slip rings and brushes, provides insights into their functionality. Slip ring motors offer high starting torque, adjustable speed control, and the ability to handle heavy loads, making them suitable for various industrial applications. This knowledge enhances comprehension of slip ring motors and their applications in various industrial settings. By understanding the working of slip ring motors, engineers and industry professionals can utilize them effectively to meet specific industrial requirements.