 |
|
|
|
|
|
|
|
|
|
|
|
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
|
 |
 |
 |
 |
 |
|
High Voltage Motors - Product Construction
Frame and Enclosure
LS’s range includes fin-cooled frames manufactured from grey cast iron, spheroidal graphite iron or fabricated carbon steel. CacA and CacW box frame motors and larger motors employing unit construction on a base plate with pedestal-mounted bearings are all fabricated from carbon steel.
Stator Winding
LS’s standard stator winding insulation is the NORFAST Vacuum Pressure Impregnation Class F system using Class H materials. The insulation system is based on mica tape and employs a split resin impregnation technique that gives a low viscosity and highly reactive system, which ensures maximum penetration with minimum drain-out characteristics. Once fully impregnated, the system provides a consolidated winding which exceeds the requirements of NEMA MG. 1-20.18 (1998) for sealed windings.
Stator windings consist of coils all having the same level of turn insulation. Each coil is formed from pre-insulated rectangular copper conductor and insulated with mica tape. For higher voltages, the slot portion includes a resistive corona shield to reduce voltage stress on the edges of core laminations. An additional semi-conducting layer is applied at the slot ends for the purpose of grading surface voltage stress.
Once coils are assembled into the open slots of the core, the end windings are securely blocked and braced for excellent mechanical strength against electrical starts and short circuit. The whole assembly is consolidated through impregnation under vacuum. The wound stator is finally baked at high temperature, whilst being continuously rotated on rollers to cure and fully consolidate the insulation system.
Stator Core Pack
The stator core is assembled from varnish insulated laminations produced at the same time as rotor laminations on an automated lamination precision punching and notching line, thus ensuring the best electrical and mechanical compatibility for rotor/stator packs. Lamination packs with the endplates are assembled onto a mandrel and consolidated before welding/fixing to produce a high integrity core pack.
Rotor
The rotor core pack is shrunk onto the shaft assembly while clamped under pressure to ensure maximum integrity. Cage-type rotors have copper or copper alloy bars brazed to jointless short-circuiting endrings of material appropriate to the electrical and mechanical Motors are normally fitted with shaft mounted uni-directional fans to minimise energy losses. requirements. Alternatives include various copper alloy bars, non-standard bar profiles or slip-ring rotors, which are available for individual applications.
Shafts are normally manufactured from either normalised carbon steel bar or carbon steel forgings. Various shaft ends are available including parallel shaft end with keyway, tapered shaft end or integral flange.
All rotors are dynamically balanced to ISO 1940/1 (BS6861: Pt 1: 1987). All rotors have at least two-balance planes. On larger and higher speed rotors, a third balance plane may be utilised.
Motors are normally fitted with shaft mounted uni-directional fans to minimise energy losses.
Bearings
Bearings are dependent on application and machine type but typically rolling element bearings are endshield mounted and grease lubricated. Some high speed arrangements may utilise a circulating oil bath arrangement. Rolling element bearings are designed to have an L10 life greater than 40,000 hours. Where required, bearings are electrically insulated to prevent damage from circulating shaft currents.
Where appropriate to suit output, duty, ambient conditions or customer-requested, oil lubricated sleeve bearings may be specified either as self-contained or force lubricated. Depending on frame size, sleeve bearings may be either endshield mounted or pedestal mounted. All sleeve bearings are supplied with oil rings, sight glasses and insulation between the bearing shell and housing; the drive end bearing is supplied with a shorting strap for normal operation. On sleeve bearings for force lubrication the oil rings provide a run down facility in the event of oil supply failure.
Single bearing machines with solid couplings, forged integrally with the drive shaft, are available on request.
For vertical machines, LS has several bearing arrangements available to suit the application. These can range from angular contact rolling element bearings, which could be either grease lubricated or oil bath lubricated, to white metal and tilting pad bearing arrangements.
Cable Terminations
Various forms of cable terminations are available including fault rated, pressure-relieved terminal boxes.
A selection of available terminal boxes includes:
- Air insulated
- Phase insulated
- Phase segregated
- BEAMA/CEGB
- Elastomeric type bushings
- Terminal enclosures to house Lightning Arrestors, Surge Capacitors and Current Transformers are also available.
