Wound-Rotor Induction Motor

Soft Start, Adjustable Speed

• Horizontal
• 100 - 15,000 hp, Up to 16,000 Volts

The wound-rotor induction motor, although more expensive than the squirrel cage motor, has some distinct application advantages. Historically it has been used for hard-to-start, high inertia fans, or where power system requirements demand a soft start. With a liquid rheostat, or a static secondary speed control, the wound-rotor is an important alternative drive where limited range adjustable speed is required.

Wound Rotor

• Versatile
• Adjustable Speed
• Soft Starts

Some applications require an induction motor with a provision for changing the impedance of the rotor winding for adjustable speed operation or soft start. The wound rotor winding is phase wound with the same number of poles as the stator so that it may be connected through its slip-rings to a variable external impedance such as the liquid rheostat or other speed control system.

The magnetic construction of the wound rotor is similar to the squirrel cage motor. However, the rotor winding is fully insulated to ground for all expected continuous and transient operating voltage levels and connected to have the same number of poles as the stator winding. Since they are subject to severe mechanical forces, the rotor winding end-turns are constrained with glass banding bonded with a high temperature, high strength, thermosetting resin.

The rotor winding is connected to the stationary control elements by collector rings mounted on the shaft. The collector rings are positioned externally to the rest of the motor, when possible, to prevent the brush dust from contaminating the rotor and stator windings.

Vibration Equipment

Seismic-type such as RobertshawTM measures overall vibration. 1-6 units are located on the frame.
Proximity-type such as Bentley NevadaTM measures the shaft vibration. 2-5 units are located on the bearing housing.
Acceleration-type such as MetrixTM measures bearing housing vibration. 1-6 units are located on the bearing housing.

Other Accessories

Whenever required, the following accessories may be supplied:

• Surge protection
• Tachometers (capacitors and lightning arresters) •
• Overspeed switches
• Current transformers
• Slide rails
• Pressure switch
• Sole-plates
• Space Heater