What is Slip Ring Induction Motor and Its Advantages
An induction motor is an electric device that converts electrical energy into mechanical energy, with its self-starting attribute making it particularly well-suited for industrial applications. Among the types of 3-phase induction motors is the slip ring induction motor, which belongs to the wound rotor motor category. This motor type offers several advantages, such as low initial current, high starting torque, and improved power factor, making it ideal for high-torque applications like cranes and elevators.
The rotor windings of the slip ring induction motor contain a greater number of windings, inducing higher voltage and lower current compared to the squirrel-cage rotor. These windings are linked to external resistance through slip rings, enabling torque and speed of the motor to be controlled.
Why Slip Rings are used?
Induction motors require slip to generate torque, which is the disparity between the flux speed and rotor speed. Slip rings facilitate power and electrical signal transmission from a fixed to a rotating component. Slip rings are electromechanical devices that enable the transfer of power and electrical signals between stationary and rotating components.
Slip rings are alternatively known as rotary electrical interfaces, electric rotary joints, swivels, or collector rings. In certain applications, slip rings necessitate high bandwidth to transmit data. By enhancing system operation and eliminating wires that hang from motor joints, slip rings elevate the efficiency and performance of a motor.
Advantages & Disadvantages of Slip Ring Motors
The slip ring induction motor has several advantages and disadvantages. Some advantages include its ability to provide high and exceptional starting torque to support high inertia loads, low starting current due to external resistance, and capability to handle full load current that is 6 to 7 times higher. However, the slip ring induction motor also has some disadvantages, including higher maintenance costs due to brushes and slip rings compared to squirrel cage motor, intricate construction, high copper loss, low efficiency and low power factor, and being more expensive than 3 phase squirrel cage induction motor.
Slip ring induction motors are commonly used in applications where high torque and low starting current are required, such as elevators, compressors, cranes, conveyors, hoists, and other similar applications.