Both wound rotor and squirrel cage rotor are types of rotors used in induction motors. They differ in their construction and behavior, which in turn affects the performance of the motor in various applications. Here's how they differ:
Squirrel Cage Rotor:
Construction: A squirrel cage rotor is made of a cylindrical laminated core with evenly spaced slots. In each slot, conductive bars (usually made of aluminum or copper) are placed. These bars are short-circuited at both ends by end rings, creating a closed loop or "squirrel cage" structure.
Starting and Running Characteristics: Squirrel cage rotors are known for their simplicity and ruggedness. They provide good starting torque and are suitable for applications that require constant speed operation, such as fans, pumps, and many industrial machines.
Speed Regulation: Squirrel cage rotors have limited speed control capability. The speed of the motor is determined primarily by the frequency of the power supply and the number of poles in the motor.
Maintenance: These rotors have fewer moving parts, making them relatively low-maintenance compared to wound rotor designs.
Cost: Squirrel cage rotors are generally less expensive to manufacture than wound rotor designs due to their simpler construction.
Wound Rotor (Slip Ring Rotor):
Construction: A wound rotor consists of a laminated core similar to the squirrel cage rotor, but instead of short-circuited bars, it has a set of insulated wire windings placed in the rotor slots. These windings are connected to slip rings at the end of the rotor shaft.
Starting and Running Characteristics: Wound rotors offer greater control over the motor's performance. They allow for external resistance to be added to the rotor circuit through the slip rings, which affects the motor's starting torque, running speed, and even speed control (to some extent).
Speed Regulation: Wound rotor motors can provide better speed control compared to squirrel cage motors. By varying the resistance in the rotor circuit, the torque-speed characteristic of the motor can be adjusted to suit specific application requirements.
Applications: Wound rotor motors are often used in applications that require adjustable speed, such as crane drives, hoists, and certain types of heavy machinery.
Maintenance: Due to the presence of slip rings and brushes, wound rotor motors require more maintenance compared to squirrel cage motors. The brushes wear down over time and may need replacement.
In summary, the main differences between wound rotor and squirrel cage rotor lie in their construction, control capabilities, and application suitability. Squirrel cage rotors are simple, reliable, and suitable for constant speed applications, while wound rotors provide greater control over motor performance but require more maintenance and are often used in applications requiring adjustable speed.