JPS63310353A - Superconductive induction motor - Google Patents

Abstract

PURPOSE:To obtain an induction motor of high efficiency, by using a temperature characteristic of a superconductive material, in which starting is performed in a normal conducting state to suppress the starting current, and by lowering the temperature of a conductor in high speed to bring it into superconducting state. CONSTITUTION:A stator winding 2, a rotor end ring 4 and a bar 5 of a squirrel cage induction motor are made of a superconductive material. In starting the motor, it is in the normal conducting region. When the starting is finished and after it comes into a steady state, the stator winding 2, rotor end ring 4 and bar 5 are cooled so that it becomes superconducting state. As a result, as the primary and the secondary resistance will be zero ohm, the primary and secondary copper loss will be zero watt and the efficiency is improved. In starting the motor, since the starting is performed in the normal conducting state, no remarkable difference is found in the conventional induction motor and the starting current. Any one of the conductors among the stator winding 2, the end ring 4 and the bar 5 can be made of the superconductive material.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an induction motor using a superconducting material as a conductor, and is particularly suitable for reducing starting current compared to conventional induction motors and operating with high efficiency at high speeds. Regarding induction motors.

[Conventional technology]

Conventionally, there were no materials that could achieve superconductivity at high temperatures close to room temperature, so induction motors were constructed using normal conductive materials as conductors. However, with the recent development of superconducting materials, it is becoming increasingly possible to obtain superconductivity at high temperatures near room temperature. In this case, the transition from normal conductivity to superconductivity or from superconductivity to normal conductivity becomes relatively easy, and it becomes possible to transition the conductor from normal conductivity to superconductivity during operation.

A related publication is JP-A-60-261356.

[Problem that the invention seeks to solve]

The above conventional technology does not consider using superconducting materials for the conductor, and by passing current through the conductor,
There was a problem that copper loss occurred.

The purpose of the present invention is to use the temperature characteristics of the material used for the conductor to perform normal conduction during startup, suppress the startup current, and
The aim is to achieve highly efficient operation by lowering the temperature of the conductor and making it superconducting at high speeds.

[Means for solving problems]

The above object is achieved by utilizing the temperature characteristics of the superconducting material to transition the conductor from normal conductivity to superconductivity during operation of the induction motor.

[Effect]

An induction motor creates a magnetic field by passing current through a conductor.
Rotational force is generated by this magnetic field and the current induced in the rotor.

At this time, if the conductor is a normal conductor, copper loss will occur, but if the conductor is made of a superconducting material, the copper loss will be reduced to OW, making it possible to operate with high efficiency. However, if the conductor is always superconducting, an excessively large current will flow during startup compared to a conventional induction motor, and excessive electromagnetic force will be applied to each part of the winding, causing damage to the winding. Therefore, by making the conductor normal conductive during startup to suppress the startup current, and then transitioning the conductor from normal conductivity to superconductivity after startup, excessive current can be suppressed and highly efficient operation can be achieved.

〔Example〕

Figure 1 shows the qualitative temperature characteristics of superconducting materials, and Figure 2 shows the T-type equivalent circuit of an induction motor.

For superconducting materials, when the temperature is below Tz, the resistance value R during normal conduction
The resistance value rapidly decreases from ', and the resistance value completely reaches O at temperature T1.

The embodiments of the present invention utilize the temperature characteristics of the above-mentioned superconducting materials.

Figure 3 shows the schematic structure of a squirrel cage induction motor.

In this embodiment, the stator winding 2 and the rotor end ring 4/bar 5 in FIG. 3 are made of a superconducting material having the temperature characteristics shown in FIG. 1. With the above-mentioned configuration, at startup, the temperature of each part is higher than T2, and after the startup is completed and a steady state is reached, the stator winding 2, rotor end ring 4,
By cooling the bar 5 below Tl and setting the primary resistance rl and secondary resistance rz in Fig. 2 to 0Ω, the primary copper loss and secondary copper loss during the power flow shown in Fig. 4 become OW, and the efficiency is reduced. will improve. Since starting is carried out in a normally conductive state, there is not much difference in starting current from conventional induction motors.

In the above embodiment, both the stator-side and rotor-side conductors are made of superconducting material, but only one of the conductors may be made of superconducting material.

〔Effect of the invention〕

According to the present invention, since a superconducting material is used for the conductor, copper loss can be eliminated, which has the effect of improving efficiency.

[Brief explanation of the drawing]

Fig. 1 shows the general temperature characteristics of superconducting materials, Fig. 2 shows the T-type equivalent circuit of an induction motor, Fig. 3 shows the general structure of a squirrel cage induction motor, and Fig. 4 shows the power flow of the motor. DESCRIPTION OF SYMBOLS 1... Stator core, 2... Stator winding, 3... Rotor core, 4... Rotor end ring, 5... Rotor bar, rl... - next winding Resistance, xi...primary leakage reactance, r2...secondary resistance, XZ...secondary leakage reactance, rQ...iron loss resistance, xo...excitation reactance.

Claims (1)

[Claims] 1. In an induction motor consisting of a stator core and windings and a rotor core and windings (or bars and end rings), the conductor of at least one of the stator windings and rotor windings (or bars and end rings) is It is characterized by being constructed using a material that becomes superconducting at a temperature below , the starting current is kept low by keeping the conductor in a normal conductive state, and the conductor is in a superconducting state at high speeds to achieve high efficiency operation. Superconducting induction motor.