General Description Of Product

The PRIMELINE® induction generator is a rotating induction machine whose electrical performance has been designed to optimize its performance as a generator. The drip-proof frame construction used throughout is as follows:

NEMA Two Bearing Units:
250 to 320 frame – rolled steel frame with cast iron end brackets.
360 to 508 frame – all cast iron construction.

Single Bearing Units:
360 frame – all cast iron construction.
430 & 570 frame – rolled steel frame with cast iron end brackets.

430 and 570 frame single bearing units are in the same mounting dimension as Marathon’s MAGNAPLUS® and MAGNAMAX® synchronous offering to provide customers with interchangeability and allow for one common rail design.

All rotors are of rugged construction. Regreasable double shielded ball bearings are used throughout. A torsionally engineered SAE engine coupling system is available for a portion of the product which is used in engine driven applications.

The listings described in the product literature are basic standard ratings. There will always be applications that will require specific design. Contact factory for your special requirements.

Generator Basics

The induction generator is similar to any other generator, as it is a device that converts mechanical energy into electrical energy.

An induction generator consists of a rotating element or rotor and a stationary element or stator. The rotor consists of an aluminum or copper ‘squirrel cage’ within the rotor laminations. The stator consists of insulated copper windings within the stator laminations. Neither an exciter nor voltage regulator is used or required.

An induction machine (motor or generator) connected to the line power source (excitation) is capable of operating in either mode. If the shaft is allowed to rotate at a speed below synchronous, the machine will attempt to operate as a motor. The rotating magnetic field vector caused by the three phase stator windings will deliver real and reactive power to the rotor as it sweeps around the squirrel cage. If the shaft is forced to rotate at a speed higher than synchronous, a change takes place within the machine. The stator magnetic field vector will continue to deliver reactive power, but now accepts real power induced from the rotor (generator mode). Now the squirrel cage is sweeping the field vector, causing a flux reversal. At synchronous speed, the line supplies reactive power and machine losses, but no torque or power is generated.

There is a practical upper limit to the speed at which an induction generator can be operated above synchronous and still generate real power efficiently. This speed is typically 2 to 5 percent above synchronous, but below breakaway torque. Above the breakaway torque speed, the real power generated decays quickly to a low value.

The induction generator and induction motor are in theory similar, but the PRIMELINE® induction generator has significant differences from standard motors: