Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1977-07-15
1979-04-17
Budd, Mark O.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 62, H02K 524
Patent
active
041503139
ABSTRACT:
An electric motor includes a motor frame and a fan driven by the motor disposed adjacent one end of and inside the motor frame. The fan draws air in through an inlet opening formed in the motor frame at the end of the frame opposite the fan. The air flows over and cools internal components of the motor and is exhausted by the fan in a radially outward direction through an outlet opening in the motor frame. A silencer for the motor includes an acoustical panel which at least partially surrounds the motor frame, is spaced from the frame, and is disposed to intercept air flowing radially from the outlet opening in the frame. The acoustical panel extends from the fan end of the motor frame partway along the length of the frame so as to direct air exhausted from the fan along the frame between the frame and the panel. The panel includes a layer of air-permeable sound absorbing material and air-impermeable sheet disposed adjacent to the sound absorbing material on the side of the material opposite the motor frame. A perforated sheet is disposed between the sound absorbing material and the motor frame. In a direct current electric motor that operates at any one of several speeds, the noise which is produced by the motor and which is emitted from the motor with the air that passes through the outlet opening in the motor frame may be characterized by a dominant pure tone that varies with the rotational speed of the fan and motor. In such a motor, the perforated sheet and the air-impermeable sheet of the acoustical panel are preferably spaced relative to each other and to the motor frame such that the two sheets define at least part of a resonant cavity tuned to the dominant pure tone produced by the air exhausted from the fan at the maximum rotational speed of the motor. By so tuning the resonant cavity, the sound absorbing material of the acoustical panel can effectively be utilized to attenuate the noise generated at other rotational speeds of the fan and motor.
REFERENCES:
patent: 2179341 (1939-11-01), Muller
patent: 2508144 (1950-05-01), Carville
patent: 2522675 (1950-09-01), Hoover
patent: 2697179 (1954-12-01), Wendel
patent: 2881337 (1959-04-01), Wall
patent: 3575524 (1971-04-01), Adjian
patent: 3980912 (1976-09-01), Panza
Budd Mark O.
Lord Corporation
Salada Maurice R.
Wright James W.
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