Standards

Repair information for electrical machinery.

Purpose
The purpose of this document is to outline the minimum standards and materials used in each step of apparatus rewinding and repairs.

Records Kept
A record of each machine received for repair is established on the date, and a job card and number is allocated.  The record includes Customer, motor name plate data (if available), condition of appliance on arrival, remarks and repairs made, bearing sizes, any miscellaneous parts used, extra repairs requires, resistance recorded, test run results recorded, also primary cause of failure determined, if possible.

Cleaning
All parts are steam cleaned and grease, dirt, oil etc is removed.  If motor windings are steam cleaned they are then dried in oven to remove moisture.  Parts (cast iron only) that are dipped in caustic hot tank are totally cleaned and then a layer of primer paint is applied.  Motors that require rewinding are placed in the hot tank (cast iron only), and upon removal of windings the stator is given a steam clean to remove any residue and then dried out in oven and primed before insertion of insulation.

Rewinding
Winding data is accurately taken and recorded and can be compared to EASA data bank or data taken from similar machine.  Stripping of windings are removed in such a manner that reduces chance of lamination damage, cast iron motors can be placed in caustic hot tank which dissolves varnish and enamel from wire leading to easy removal or a light heating process (gas burner) is used to remove wire.  Stators are cleaned of all foreign materials, particles of dirt, grease or oil before insulation is placed in slots.  Upon motors being rewound they are slightly warmed and then totally immersed in varnish tank to ensure full penetration of varnish into windings, and then baked to harden.  Motors are then cleaned of excess varnish, and parts cleaned and assembled with new bearings being fitted.

Testing
Motors are insulation tested, resistances taken and recorded, test run on star delta started no load and readings recorded.

Exterior Finish
All rewound and overhauled motors are externally cleaned and painted to either customer’s choice or close to original motor colour.

Materials Used

  • Copper Wire – Polyester Imide PEI-2 – Class ‘H’ (180 deg. C)
  • Slot insulation - Pyrolam 5-5-5. 3-3-3, 2-2-2 – Class ‘F’ (155 deg. C)
  • Phase insulation – Varnished Glass Fabric – Class ‘B’ (130 deg. C)
  • Phase insulation – Pyrolam 5-5-5, 3-3-3, 2-2-2 – Class ‘F’
  • Wire Sleeving – Vidaflex SEP – Class ‘H’
  • Tapes – Plain glass & Polyglass – Class ‘H’
  • Varnish – Isonal 31-398 – Class ‘F’
  • Lead Cable – Silicon Rubber Glass Braid
  • Heat shrink used over large motor connections
  • Paints – Enamel – Various colours
  • Bearings – SKF or NTN
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