Superior Design

Ventilation and Cooling

A new design was developed to improve heat exchange with a low-pressure drop.

• A new internal fan was developed to match internal airflow requirements.
• For TEAAC enclosures a new external fan design was developed to match cooler characteristics and reduce noise.
• Heat is dissipated much more efficiently due to a redesign in the internal air flow circuit configuration which increases the heat exchange area and air flow.

Improved ventilation and cooling has been achieved with a new internal fan design. This allows the Pegasus MHV motor to match internal air flow requirements.

Low Vibration

A dramatic reduction in vibration due to design changes has been realized. The PegasusTM MHV exhibits a low vibration, low thermal vector and slow roll, meeting API-541 requirements. This was due to a major focus on design and process improvements.

Inverter Duty / Reliability

VFD applications are best served by these machines with strict adherence to NEMA MG1 part 31 and IEEE-522 figure 2 (or figure 1 if requested). They include an insulated bearing and shaft grounding brush which decreases the possibility of circulating shaft currents.

Meets API 541 4th Edition and API 547 for Petroleum & Chemical Applications

Vibration and total electrical/mechanical run out levels meet stringent API 541 4th Edition standards which translates to increased motor uptime and an improved overall reliability. A test system compatible with vibration sensoring methods, normally used in Oil & Gas applications, allow a high sampling rate acquisition for vibration recording and is capable of recording frequency spectrums and polar plots. Use of a dual frequency heat run test minimizes erroneous vibration compared to a motor coupled to a dynamometer.

Reduction of High Harmonics

Using the latest engineering simulation tools and modern modal testing equipment made it possible for GE to design a stator which reduced the possibility of operating close to high amplification regions. Flexible or rigid shaft construction may be used based on specific application requirements and design criteria. This is critical when a motor is mounted to a compressor or pump skid.

Stator Construction

Stator laminations are precision punched from high quality, low loss electrical sheet steel with a thermally stable insulating film. Most ratings are of rectangular frame construction, utilizing packaged cores. The magnetic core consists of laminations compressed for mechanical strength and completely wound before the core package is inserted into the frame. This construction permits free access to the coil end-turns during manufacture and simplifies insertion of the winding and bracing systems. This visual accessibility also helps to ensure increased quality in manufacturing.

Redesigned stator frames using powerful engineering tools such as FEA, which significantly reduce overall vibration levels.

The stator assembly was configured for increased air flow which improved heat transfer and led to a more compact design.

Insulation Construction

More than 30 years of successful field experience proves the reliability of the insulation system. In addition to providing the necessary electrical insulation, this system meets all the stringent mechanical and thermal requirements found in modern applications. pegasusTM MHV products use an epoxy solventless resin vacuum-pressure- impregnation (VPI) process to unite superior insulation materials into a complete insulation system assuring long life. For line voltages of 5000 Volts and above, a semi-conducting armor is applied to the slot portion and graded beyond the core to provide corona protection. The binding agent used in this case is GE's third generation epoxy resin, selected and tested to IEEE-429 and IEEE-1043. The coils receive a protective armor of heavy glass tape for protection against mechanical shock and abrasion.

GE's Custom Polyseal insulation system is also available upon request. Custom Polyseal is a sealed winding insulation system which meets NEMA MG1 1.27.2 and passes the test criteria for 12.62 and 20.18. It is designed to meet severe operation conditions and have resistance to moisture penetration, oil, chemicals and salt water.

Rotor Construction

The “squirrel cage” induction motor is a rugged yet simple combination of shaft, magnetic circuit and electric winding. The magnetic circuit consists of punched thin steel discs assembled to form a laminated magnetic core mounted on the shaft. The laminations are coated with a temperature stable insulating film to reduce magnetic losses yet maintain dimensional stability in the face of severe thermal and mechanical stresses. The rotor winding consists of a number of uninsulated metal bars in the outer surface of the magnetic core parallel to the shaft and short circuited by metal rings at both ends.

Standard Rotor Features:

• Aluminum bar rotor is standard.
• Copper bar rotor is available to meet API 541 4th Edition and is standard on 2-pole 8213 frame and larger motors.
• A 2 pole machine includes a 5 plane "step" balancing standard - when flexible shaft is utilized, this assures best vibration for increased performance and life.
• 4140 shaft steel material on 2 pole machines. Other speeds may use 1045 shaft steel.

Fabricated aluminum rotor construction is typically included. Copper bar rotor construction is available to meet API 541 4th Edition.

Bearings

Self-aligning spherical seat sleeve bearings per DIN 31693. These bearings employ construction features and sealing systems designed to keep the oil in and the dirt out. Seal additions are also available to meet IP-55 requirements (dust and water jet proof).

• The babbit-lined bearing shell is supported by a rugged housing and employs an oil ring that carries the oil from the reservoir up to the bearing.
• Flood lube systems are employed on 2-pole designs above 2750 HP. The bearings are insulated to eliminate damaging shaft currents.
• Sight holes and split construction allow easy inspection and replacement, without uncoupling the drive load.
• Antifriction bearings are available for smaller ratings.

The endshield and internal ventilation circuit was modified to improve air circulation. This translates to a cooler operating bearing.