JPS6264233A - Squirrel-cage rotor - Google Patents

Abstract

PURPOSE:To obtain a squirrel-cage rotor with a good torque characteristic by providing an insulating layer between the rotor core and its conductor. CONSTITUTION:A coating layer 3 of Fe3O4 is provided on the inner surface of a slot 1a of a rotor core 1 and interposed between a rotor conductor 2 and the rotor core 1. The resistance of this Fe3O4 is so much higher that it is possible to afford the leak protection against the current which flows along the rotor conductor 2. Thus a squirrel-cage rotor of an induction motor is obtained which does not incur much stray load loss but shows good velocity torque characteristic.

Description

[Detailed description of the invention] [I branch field to which the invention pertains] The present invention relates to a squirrel cage rotor for an ej411L motive.

[Prior art and its problems]

In general, the @411 type squirrel cage rotor is shaped like a disk, with a hole in the center for fitting the shaft, and a slot made of aluminum or aluminum alloy along the circumference. The side cross section of the manufactured squirrel cage rotor is shown in Figure 2.
A conductor made of aluminum or the like is cast into the slot la.

By the way, since the conventional rotor core 1 is formed by press punching, the insulating coating layer is exposed on both sides. Therefore, the current flowing in the rotor conductor leaks through the iron core to adjacent conductors and the rotating shaft. As a result, the eddy current loss and stray load loss of the rotor increase, and the torque τ of the induction motor increases as shown by the solid line in Fig. 3.
As shown in curve 7, the rotational speed V temporarily decreases during the increase,
This causes deterioration of the characteristics by increasing the amount again.

As a countermeasure against this problem, there are methods such as immersing the rotor core in an insulating paint made of organic resin and drying and hardening the paint adhering to the inside of the slot, or applying water glass to the inner surface of the slot and baking it.

However, the insulating film layer produced by this method has the disadvantage that it cannot withstand the low heat resistance temperature (680' to 750'C, which is the casting temperature of aluminum, aluminum, etc.), and it is difficult to improve the torque characteristics of induction motors. This has not yet been achieved.

[Purpose of the invention]

An object of the present invention is to provide a squirrel cage rotor with good torque characteristics by providing an insulating layer between a rotor core and its conductors to eliminate leakage current.

[Key points of the invention]

The present invention provides a squirrel-cage rotor in which rotor conductors are cast into slots in a rotor core in which a plurality of electrical iron plates are laminated, in which a Fe3O4 film layer is formed between the slots and the trochanter conductors. This was done by focusing on the fact that the Fe5C)4 (magnetite) coating layer produced in the slots of the rotor core through steam treatment has high electrical resistance and can withstand the casting of aluminum and other materials.

An embodiment of the present invention will be described in detail based on FIG. In FIG. 1, F
A coating layer 3 of e3O4 is provided and interposed between it and the rotor conductor 2. Since the electrical resistance of this Fe3O4 is extremely high, leakage of current flowing through the rotor conductor 2 can be prevented. It has been previously known that when superheated steam is applied to iron heated to around 570℃, Fe3O4 is produced on its surface, which is dense, has strong adhesion to the base material (iron), and has excellent heat resistance and rust resistance. known from. In this way, when a Fe3O4 film layer is generated in the slot by steam treatment, the water vapor penetrates into the gaps between the laminated punched boards, and also penetrates into the gaps between the interlayer insulation layers that were peeled off when the punched boards were formed. It also has the effect of forming a film layer of Fear 4 to fill the gaps between the laminated layers, preventing the intrusion of molten aluminum, ram, etc., and preventing a decrease in resistance between the punched plate layers, and increasing the speed of the induction motor (v -) The τ characteristic improves as shown by the broken line in the third garden.

The conditions for this steam treatment are such that the iron core is heated to 560° to 600° C. and the steam treatment is carried out at 1 atm for 15 to (a) minutes, and the treatment is simple. It has also been experimentally confirmed that this has the secondary effect of releasing the strain generated during press punching and improving the magnetic properties of the electric iron plate.

〔Effect of the invention〕

As described above, according to the present invention, cracks can be removed between the rotor conductor and the inner surface of the core slot using a simple and inexpensive method such as steam treatment! By forming a film of Fe5 (J4) as a green layer, it is possible to prevent leakage Za between the rotor conductor and the rotor core, resulting in an induction motor with low stray load loss and good speed-torque characteristics. There are advantages that a squirrel cage rotor can provide.

[Brief explanation of drawings]

FIG. 1 is a sectional view near the slots of a squirrel-cage rotor showing an embodiment of the present invention, FIG. 2 is a sectional view near the slots of a squirrel-cage rotor showing a conventional example, and FIG. This is the speed-torque curve of the squirrel cage rotor shown in Figure 2. DESCRIPTION OF SYMBOLS 1... Rotor core, la... Slot, 2... Rotor conductor, 3... Fe3O4 film layer. Figure 1 Figure 2 @ Figure 3

Claims (1)

[Claims] 1) In a squirrel-cage rotor in which rotor conductors are cast into slots in a rotor core made up of a plurality of laminated electrical iron plates,
A squirrel cage rotor, characterized in that a film layer of Fe_3O_4 is formed between the slot and the rotor conductor.