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Synchronous Motors

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TECO-Westinghouse Motor Company synchronous motors and generators provide superior value in terms of proven reliability, low maintenance performance and long life in any application. Our synchronous machines offer numerous benefits including:

  • Constant-speed operation
  • High efficiency ratings
  • Low inrush currents
  • Leading power factor (for corrective KVA capability)

These features make them the optimal choice for many industrial drive applications.

Power factor improvement is one of the most attractive considerations in selecting a synchronous machine. Synchronous motors operate at leading power factors and are available with rated power factors ranging from unity to leading. Thus they can produce substantial savings by supplying kvar's to counteract lagging power caused by other inductive loads.

Features:

Applications

For Unequalled Dielectric Strength and Voltage Endurance

TECO-Westinghouse Motor Company synchronous machines are customized to the specific requirements of each application. Because of their unique features, high operation efficiencies, and adaptability to all working environments, synchronous motors and generators are the logical choice for a multitude of industries. These include pulp and paper processing, electric utility, marine, water and wastewater treatment, chemical and petrochemical, steel, mining, cement, and air separation...

Synchronous machines can be found wherever there is a demand for highly efficient, cost-effective, dependable machines. They are frequently used for rolling, ball and sag mills, chippers, mixers, pulp refiners, pumps, fans, and compressor (reprocating and centrifical) drives.

They can be furnished with adjustable frequency drives (PWM, LCI, and Cyclo-converter) for soft starters or speed regulation.

With all of the advancements made in adjustable frequency drive technology, the variable speed synchronous motor is a logical choice for applications requiring high torque at low speed with a high-speed range.

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High Efficiency Design

TECO-Westinghouse Motor Company synchronous machines feature high efficiency designs in which great care is taken to minimize losses. Various design features are manually selected to ensure maximum operating efficiencies and trouble-free operations:

  • Airgap, slot openings and slot ratios are selected to reduce pole face losses due to flux pulsations.
  • Low loss, core-plated, non-aging silicon steel stator punching of various dimensions are selected to reduce core losses.
  • The stator copper is stranded to minimize eddy current losses.
  • The number of stator slots, slot width, slot depth and stator core depth are dimensioned to reduce magnetic noise.
  • Pole punchings are designed for reduced pole leakage flux and field excitation to reduce field copper losses.
  • Blowers are carefully selected to reduce windage loss and provide maximum cooling. This helps reduce the overall machine size.
  • Stator end-plates are designed to ensure a tight and rigid core assembly, to minimize noise due to core distortion and to transmit torque to the frame bulkhead.
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Split-Sleeve Bearing System

The bearing system has been designed and engineered for continuous, reliable performance and easy maintenance. Sleeve-type bearings and oil rings are split to provide accessibility for visual inspection and maintenance. A void-free centrifugally cast babbitt is bonded to thick-walled bearing shell designed with spherical seating surfaces. Carefully balanced bronze oil rings and oil accumulating grooves in babbit-lined oil ring guides provide a liberal supply of lubricant to the bearing.

The bearing unit includes a four part bearing seal system designed to prevent unwanted leaks. The seal system consists of an inner and outer floating labyrinth oil seal and an inner and outer air seal. These seals work together to contain oil in the bearings while keeping dirt and contaminates out.

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Copper Rotor Construction

TWMC high-speed synchronous machines feature a time tested and proven rotor construction design. For high torque transmission throughout its variable speed range, the rugged construction of these premium rotors are without equal.

The rotor construction starts with a high strength alloy steel shaft forging that is precision machined, ground and finished to our exact tolerances. Next the rotor spider is constructed from massive steel laminations and machined to mate with the shaft to form the rotor core assembly. Dovetail slots are then milled into the spider to accept the dovetailed pole pieces that are secured in place by tapered keys. Dovetail pole construction (pictured below) ensures a secure attachment to the shaft and spider.

Rotor poles are stacked from thin laminations bolted together to form the pole pieces. Field coils are edge-bent and strap wound, then insulated with a custom-designed thermosetting turn insulation system before being installed onto the rotor poles. Coils are staggered to allow for efficient heat transfer and are solidly braced at the final assembly stage.

Amortisseur windings use copper/copper alloy damper bars and segments. A shaped copper interconnect between adjacent poles alleviates thermal stresses which occur during starting.

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High Quality Stator Laminations

Stator laminations are accurately die-cut from thin, non-aging, high grade precoated silicon steel, which has been insulated on both sides to minimize core losses. The stator core is built up from these silicon steel segmental punchings and held under pressure between two endplates by through bolts that are tightly torqued and tack welded. Additionally, a set of core bars is welded to the stator core and to the endplates to insure tightness, torsional stiffness, and adequate transmission of airgap torque to the motor foundation. The result is a permanently tight and concentric core with uniform airgap. An exclusive TECO-Westinghouse punching design prevents the laminations from becoming dislodged.

Thermalastic Epoxy Insulation

The stator insulation system for our synchronous machines is Thermalastic Epoxy Insulation. This is a premium insulation system, developed by Westinghouse and proven in more than thirty years of outstanding performance on thousands of Westinghouse motors and generators. Thermalastic is under continuous development to maintain its position as the world’s finest. The outstanding record of Thermalastic can be attributed to the fact that it is a mica-based insulation system. Mica has long been recognized as the most reliable insulating material due to its superior dielectric and voltage endurance capabilities.

Careful manufacturing procedures, including rigorous testing at critical points in the process, assure a distinctly superior insulation system. First, mica insulation is applied to the formwound stator coils. The coils are then installed in the slots and the completely wound stator is post-impregnated with epoxy resin in a vacuum pressure tank. Next, it is transferred to a baking oven for resin polymerization. The cycle is repeated for double protection. The result is a stator insulation system free of corona-generating voids, able to withstand prolonged voltage stresses, moisture, abrasion, dirt, thermal cycling, and frequent starting surges.

Various types of Thermalastic insulation are used depending on the physical size and voltage rating of the machines. On machines over 7000 volts, slot sections of the insulated coil are wrapped with a semi-conducting tape which, in conjunction with a corona-suppressing semi-conducting coating applied at the ends of the straight portion, protects the stator from corona damage. For very large diameter machines, Thermalastic insulation is applied to individual coils. Each coil is vacuum-pressure impregnated with solventless resin and cured before being wound into stator core slots. An additional resilient elastometric outer coating is available for applications in which the insulation is subjected to abrasive atmospheres.

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Brushless Excitation

Brushless excitation with the TECO-Westinghouse exclusive PULSE/SYN control is available for all synchronous motors and generators for fixed speed and line start applications. It is well suited for installations such as refineries and chemical process plants requiring low maintenance and elimination of sparking.

The TECO-Westinghouse brushless excitation system consists of a field discharge resistor, diodes, SCR’s a gating module and a synchronizing module. The discharge resistor is shunted across the motor field during starting. At the proper slip and phase angle, the resistor is removed automatically from the field circuit and DC current is applied to the field to pull the motor into synchronism.

The key to the Pulse/ SYN system is the synchronizing module. This module has two separate functions. The first function is phase angle synchronization. The module monitors rotor speed (by frequency of induced field voltage) and rotor phase angle (by phase angle of induced voltage). When the speed and phase angle are such as to cause minimum disturbance to the supply system the field voltage is applied and the motor "pulls-in" to synchronization.

The second function of the synchronizing module is to handle the occurrence of "post-synchronization." This is when the motor synchronizes by reluctance before the field voltage is applied. The module monitors the rotor speed and excitations voltage. When the frequency of induced field voltage is zero for a predetermined time and excitation voltage is available, the field voltage is applied to the motor field. This action places the rotor in proper phase position and synchronization.

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Motor Testing

TECO-Westinghouse Motor Company synchronous motors and generators are tested to ensure compliance with specific performance requirements. Standard commercial tests per NEMA MG1 Part 21 include a check of winding resistances, mechanical vibration, insulation resistance, reading of field current, (stator and exciter), through visual and mechanical checks, bearing temperature rise, and airgap measurement. When required, testing procedures include noise tests per IEEE 85, as well as a complete engineering performance test per IEEE 115 to determine machine efficiency, temperature rises, starting characteristic, and other performances.

Brush Excitation

TECO-Westinghouse synchronous motor are also available with brush rigging and collector rings. The complete assembly is designed for long life and is easily accessible for inspection and routine maintenance. Made of steel or other suitable materials, the collector rings are shrunk onto a steel mandrel over a Micarta insulation sleeve. The assembly is held in place on the motor shaft by a tight press fit. To ensure permanent concentricity, collector ring surfaces are machine finished and polished after assembly on the rotor shaft. The brush rigging consists of cast-brass brushholders mounted on insulated steel rods, which are supported from the bearing pedestal. The number of brushes for a particular sized and rating depends on the field current, and sufficient brushes are supplied to limit the current density to a low value for trouble-free operation. Brushes are of the electrographitic type and are specially selected for each application.