Patent GB-164114-A (GB)
Title: Improvements in or relating to dynamo-electric machines
IPC: H02K9/197
Filed: 1920-03-01
Abstract: 164,114. Field, A. B., and Metropolitan- Vickers Electrical Co., Ltd. March 1, 1920. Armatures and field magnets, cooling; coils and conductors; casings; carcase structures; enveloping in special media.-The stator space of a dynamo-electric machine is separated from the rotor space bv a fibrous cylindrical sheath and is cooled by a circulation of insulating liquid while the rotor is cooled by an independent forced circulation of liquid such as water through ducts in the rotor, means being provided to relieve the pressure in the rotor casing due to expansion of the liquid through temperature rise, such as that caused by a short-circuit. The sheath may contain magnetic material and means may be provided for evacuating the air from around the rotor. The rotor is enclosed by a casing 3 and end bells 5, Fig. 2, and oil which enters the annular spaces 13 passes into the spaces 14, circulates around the coil overhangs 8, and flows through the axial and radial ducts 12, 15 in the stator to a central discharge space 16 open to atmosphere at 35 and having an outlet at 17. The circulation is effected bv a pump 37, Fig. 1, through the casing 3 and a cooler 38, the cooling medium of which flows through pip,es 39, 40. Loaded valves 33 at the top of the spaces 14 are so set as to allow the oil to pass to the receiver 16 through pipes 34 when the pressure reaches a predetermined limit, and explosion doors 28 cpen, by fracture or otherwise, to direct the oil to free exits 30 in the event of heavy short-circuits. Bypasses 36 around the valves relieve the oil vapour which arises during normal warming up. The sheath 9 in the air gap is preferably made of paper or canvas impregnated with a cured phenolic condensation product and is secured by a double stuffing-box 25, 26, the inner member of which 26<a> closes the rotor tunnel and contains an airtight stuffing-box 27 for the rotor shaft. The space 45 is preferably scavenged with water at a lower pressure than that of the oil so that any oil leakage is limited to an outward direction and is washed away. The sheath may contain magnetic material, such as cotton-covered iron wire of rectangular section, optionally limited to. the region opposite the core, and the sheath may be protected against damage consequent upon faults in the stator coils 7 by setting these back in their slots and filling the slot mouths with inert material. The rotor cooling water enters through a pipe 19 separated at 23 from the axial bore 21, and flows through the bore to radial ducts at the left-hand of the rotor, longitudinal ducts 18 and radial ducts 24 behind the separator 23, whence it passes out at 22. The inner stuffing-box 26 of the sheath may be flooded with water at a higher pressure than that in the space 45 and the entry of air in the rotor space prevented. For reducing rotor windage losses, the rotor space may be kept at a partial vacuum through a pips 44, Fig. 1, connected to an air pump or ejector operated by low-pressure steam from the turbine driving the machine, or, through a non-return valve, to a stage of the turbine near the condenser. Refererce has been directed by the Comptroller to Specification 165,046.