Dynamoelectric machine having coil windings and core encapsulated with resin-filler composition

A dynamoelectric machine comprising a stator assembly including coil windings and a core encapsulated with a heat-dissipating, electro-insulative housing, a rotor assembly including a shaft centrally disposed thereto, and a bearing assembly, disposed to the stator assembly, for rotatably supporting the shaft, wherein the housing is made of a cured resin-filler composition comprising:

• (I) a liquid unsaturated polyester resin containing a polymerizable vinyl monomer and a curing catalyst, which has a viscosity of from 50 to 50,000 centipoises at room temperature;
• (II) an inorganic, electro-insulative filler consisting essentially of,
• (a) a calcium carbonate powder, which passes a 325 mesh sieve,
• (b) a mineral particulate which passes a 12 mesh sieve and is retained on a 150 mesh sieve, and
• (c) a chopped glass fiber having a length larger than 200 .mu.m and a diameter less than 50 .mu.m;
• and
• (III) a clay powder which passes a 325 mesh sieve, wherein the ratios by weight of the respective ingredients are as follows:
• (a)/(b) = 0.3 to 4, (c)/total weight of the composition = 0.05 to 0.25,
• (I)/total weight of the composition = 0.1 to 0.4,
• (II)/total weight of the composition = 0.45 to 0.85, and
• (III)/total weight of the composition = 0.05 to 0.15.

A dynamoelectric machine comprising a stator assembly including coil windings and a core encapsulated with a heat-dissipating, electro-insulative housing, a rotor assembly including a shaft centrally disposed thereto, and a bearing assembly, disposed to the stator assembly, for rotatably supporting the shaft, in which interstices between the coil windings and cavities are rigidly and voidlessly filled with a cured article and the outer surface of the housing is exposed to the atmosphere so as to dissipate heat generated by operation of the dynamoelectric machine, wherein the cured article has a coefficient of linear thermal expansion less than 3 .times. 10.sup.-5 cm/cm/.degree. C. and is made of a resin-filler composition comprising:

• (I) a liquid unsaturated polyester resin composition containing an ethylenically unsaturated compound monomer and a curing catalyst, which has a viscosity of from 50,000 to 50 centipoises at 25.degree. C.;
• (ii) an inorganic, electro-insulative filler consisting essentially of,
• (a) a calcium carbonate powder which passes a 325 mesh sieve,
• (b) an inorganic mineral particulate, at least 95% of which passes a 12 mesh sieve and is retained on a 200 mesh sieve, and
• (c) a glass fiber having a length larger than 200 .mu.m and a diameter less than 150 .mu.m;
• and
• (III) a clay powder which passes a 325 mesh sieve, wherein the ratios by weight of the respective ingredients are as follows:
• (a)/(b) = 0.3 to 4, (c)/total weight of the composition system = 0.05 to 0.25,
• (I)/total weight of the composition system = 0.1 to 0.4
• (II)/total weight of the composition system = 0.45 to 0.85, and
• (III)/total weight of the composition system = 0.05 to 0.15