Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1989-04-04
1991-03-19
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Rotary
310197, 310212, 310216, 310265, H02K 122, H02K 1702, H02K 100
Patent
active
050013807
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to electrical engineering, and more particularly to electric asynchronous motors with a solid electromagnetic rotor. The present invention can be most successfully used in electric drives designed to control pipeline valves or other apparatus, where it is required to provide a high starting torque of the motor and the minimum dynamic overloads in the actuator, as the motor is braked.
PRIOR ART
Currently, an extensive use of asynchronous motors is caused by their being simple in construction and reliable in operation. The serious drawbacks of asynchronous motors, however, reside either in their low starting torque or in a high nominal rotational speed of the rotor. These disadvantages both result in certain negative effects in the actuator that is to be controlled by the asynchronous motor. The low starting torque of the motor fails to ensure a reliable removal of the stop member from the valve seal, while the high nominal rotational speed of the rotor leads to significant dynamic overloads occurring in the actuator as a result of a hard braking of the motor. Consequently, the development of asynchronous motors designed to control the valves aims to increase the starting torque and reduce the nominal rotational speed of the rotor.
Known in the art are asynchronous motors comprising a stator and a rotor formed by a solid ferromagnetic cylinder ("Elektrichestvo", No. 2, 1926, (Moscow), K. L. Shenfer "Rotor asinkhronnogo dvigatelya v vide massivnogo zheleznogo tsilindra", pp. 86-90).
Such motors feature a small starting torque resulting from a high value of the starting resistor of the rotor, which is due to a low electrical conductivity of the rotor material. Therefore, the use of such motors in the drives for controlling the apparatus that requires a large starting torque, such as the stop valves of the pipelines, results in degradation of mass-and-size performance of the driving means.
Also known is an asynchronous motor comprising a stator, a rotor including a core and a screen rigidly attached thereto and composed of an iron-containing alloy of high electrical conductivity ("Elektrotekhnika", No. 3, 1970, (Moscow), V. S. Mogilnikov, A. N. Strelnikov "Perspektivy uluchshenia kharakteristik asinkhronnykh dvigatelei s massivnym rotorom").
The provision of a screen in said rotor, which is made of an iron-containing alloy of high electrical conductivity, brings about an increase in the starting torque of the motor. This increased starting torque of the motor, however, results in a higher nominal rotational speed of the rotor, i.e. the speed developed under steady-state conditions of motor operation. Since the closure of the stop valves is accompanied by a hard braking of the motor with its rotor moving at a high speed, large dynamic overloads are produced in the stop valves, whereby the reliability of valve operation is impaired.
DISCLOSURE OF THE INVENTION
The principal object of the invention is to provide an asynchronous motor including a rotor with its screen so designed that, while maintaining a sufficiently high starting torque of the motor, the nominal rotational speed of the rotor is caused to be reduced with the consequent decrease of dynamic overloads in the actuator, as the rotor is braked, thus ensuring a more reliable operation of the valves.
With this principal object in view there is provided an asynchronous motor comprising a stator, a rotor including a core and a screen rigidly mounted thereon and composed of an iron-containing alloy of high electrical conductivity, wherein, according to the invention, the screen exhibits a multilayer structure, each succeeding layer in the direction towards the rotor axis being made with a decreasing electrical conductivity.
The multilayer structure of the rotor screen with the electrical conductivity of each layer decreasing towards the rotor axis brings about an increased rotor resistance as compared to the single-layer screen of the same thickness as the multilayer one. The nominal moment at the rotor is
REFERENCES:
patent: 4409506 (1983-10-01), Ito et al.
"Elektricheskie mashiny", by Ju. A. Kulik, Vysshaya Shkola (Moscow), 1966, pg. 243.
Elektrichestvo, No. 2, 1926, (Moscow), Shenfer, "Rotor asinkhronnogo dvigatelya v vide massivnogo zheleznogo tsilindra", pp. 86-90.
Elektrotekhnika, No. 3, 1970, (Moscow), by V. S. Mogilnikov et al., "Perspektivy uluchshenia kharakteristik asinkhronnykh dvigatelei s massivnym rotorom", pp. 13-16.
Klotsvog Grigory N.
Plotnikov Andrei D.
Popov Nikolai P.
Talyshinsky Israfil T.
Tretyakov Evgeny A.
LaBelle C.
Stephan Steven L.
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