Superior Construction

Stator Frame And Magnetic Core

• Strong
• Accessible
• Long and Trouble Free Life

Designed to provide optimum physical protection and good accessibility for inspection. The heavy duty stator frame and end-shields are made of fabricated steel or cast-iron ribbed-construction to maintain alignment. Stator laminations are precision punched from high quality, low loss electrical sheet steel and coated with a thermally stable insulating film. Most ratings are of rectangular frame construction, utilizing packaged cores. The magnetic core consists of laminations highly 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.

Coil Insulation

Special care is taken at the coil lead termination during taping to assure the filling of all voids at this critical point.

Once assembled, the coils are inserted into the stator slots and the end connections are brazed and taped. GE’s Coil Lock bracing system supports the coils and makes the entire structure more rigid.

Insulation System

• High Dielectric Strength
• Stable
• Contaminant Resistant

This insulation system helps to ensure long life and reliability and meets the stringent mechanical and thermal requirements of todays applications. One material alone does not have all the properties needed. Therefore an epoxy solventless resin vacuum-pressure-impregnation (VPI) process is used to unite superior insulation materials into a complete insulation system creating a reduced voids structure and assuring long life and reliability. The insulation begins with the strand insulation materials selected for the individual machine design on the basis of expected surge levels, operating temperature and system compatibility. The turn insulation materials range from several types of enamel insulation, or double polyglass insulation to micaceous tape covering each turn or conductor group.

Insulation System Quality Assurance

Many tests are made during the manufacture of the windings to assure that each machine meets the high standards set for quality materials and manufacturing processes. High potential tests are conducted at various stages of manufacturing. Following insertion of the coils into the stator slots, each coil is subjected to an impulse test of the turn insulation. Finally, prior to shipment, the standard IEC high-potential test of twice rated voltage plus 1000 volts is applied to the completed stator. When required, a sealed winding conformance test is provided as an option.

Balancing

After assembly, all rotors are dynamically balanced to the API 541 balancing grade to achieve quiet running and long bearing life. API 541 balancing grade is less than one-third of the ISO 2.5 balancing grade usually adopted by the industry. Step balancing techniques according to API 541 are applied to all 4-pole spider shaft designs and all 2-pole machines. All 2-pole flexible rotor designs have a central rotor balancing plane according API 541. The balancing machines are capable of balancing even the largest rotors prior to assembly. The completed motor is run at no-load rated voltage and frequency for a final check to make certain vibration is within the required limits. This sophisticated vibration monitoring system meets API Standard requirements.