JPS6047829B2 - Magnetic flux detection method for rotating electrical machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic flux detection method for a rotating electrical machine that derives an actual value of a secondary current of the rotating electrical machine without using a contact mechanism such as a slip ring with a rotating body.

As a means of dynamically operating an AC rotating electrical machine, there is a so-called vector control method, which uses magnetic field orientation control based on the actual values of the spatial position and magnitude of the main magnetic flux in the air gap.

For this purpose, it is ideal to detect the secondary current of the rotating electric machine, that is, the magnetic flux caused by it, without contact. Here, the present invention attempts to provide a method in which a desired magnetic field can be detected by arranging two magnetic field detection elements on the air gap surface of the stator.

The principle of the present invention is as follows. For example, as shown in FIG. 1, when a current is passed through the conductor 1 toward the surface of the paper, magnetic flux is generated, which is represented by a dotted line and has the direction of the arrow.

Therefore, it can be seen that, on the same line, the phases of the magnetic flux components in the y-axis direction differ by 1800 electrical degrees at points A and B, which are equidistant from the center of the conductor 1 on the X-axis in FIG.

FIG. 2 is an explanatory diagram of one embodiment of the present invention.

For example, consider the stator air plane of a squirrel cage induction motor with a rotor with skewed conductors. Now, Figure 2 is a partially developed view of the rotor projected onto the stator gap plane, where 3 is the conductor, 4 is the short-circuit ring, θ is the skew angle (mechanical angle), and is the rotor core thickness. is the slot pitch of the rotor projected onto the stator gap plane, m is its center line, a is the axis of the rotor, Al
,A. is the position of the object with respect to the centerline m separated by a distance 1. Therefore, the point at which the permeance of the lotus tin rods becomes the same can be derived by considering the skew angle θ.

When the conductors of the squirrel cage rotor are skewed, the secondary current flowing through the conductors is divided into an axial component and a circumferential component.

If we observe the magnetic field generated by these on the stator gap plane at two points A1 and A2, which are spaced apart by a distance l on the same axis a direction line (equation 1) and symmetrical with respect to the center m of the core thickness, we can see that the axis The magnetic fluxes produced by the currents in the directional components have the same phase, but the phases of the magnetic fluxes produced by the currents in the circumferential direction differ by 1800 electrical degrees.
Furthermore, when looking at the rotating magnetic fields, they are in the same phase. Therefore, by installing a magnetic field detector and subtracting the detection outputs of the two, that is, finding the difference, only the amount of magnetic field created by the circumferential component of the current flowing through the conductor remains, and in the end, it becomes the secondary current. It is possible to take out a proportionate amount. Here, as points of salient poles having the same permeance, there is also the intersection of the center line m and the axis a.

FIG. 3 shows a cross-sectional view of another embodiment of the invention.

5 is a motor stator, 6 is a rotor, 7 is a frame, 8 is a coil end, and 10 and 11 are magnetic field detectors.

In other words, in this other embodiment, the stator 5 and rotor 6 of the electric motor are
Instead of installing a magnetic flux detection element on the air gap surface, magnetic field detectors 10 and 11 are installed on the stator core so as to be able to detect magnetic field components parallel to the cross section including the rotor axis. .

However, the magnetic field detector 1 is installed on the inner peripheral surface of the stator 5, which faces the rotor 6 through an air gap, at a distance of 1 for which equation (1) holds.
It is clear that 0 and 11 may be installed. The secondary current of conventional motors is derived by calculation, excluding the windings, but if the temperature of the rotor changes, the resistance value will change, and the actual value of the current will differ from the calculated value.

This means that when performing control, the command value and actual value are different, making it impossible to perform good control. According to the present invention, the actual value of the current can be obtained without contact, regardless of the surrounding environment such as a temperature change in the circuit constant of the rotor, and the operation of the rotating electric machine can be properly controlled.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between conductor current and magnetic flux, FIG. 2 is an explanatory diagram of one embodiment of the present invention, and FIG. 3 is a diagram of the configuration of another embodiment of the present invention. 1...Conductor, 2...Magnetic flux, 3...
...Rotating electric machine secondary conductor, 4...Short-circuit ring, 5...
...Stator, 6...Rotor, set the center line of the core in the stacking thickness direction Ml7...Frame, 8...
... Coil end, 10/11 ... Magnetic field detector, a ... Rotating electric machine rotating shaft.

Claims (1)

[Claims] 1 In the stator gap plane of a motor equipped with a rotor with skewed conductors, l = (t_2/2)cotθ t_2 is symmetrical with respect to the center of the core thickness and for a mutual distance l, Magnetic field detectors were installed at two points such that the slot pitch of the rotor projected onto the stator air gap surface, and θ was the skew angle (mechanical angle), and the difference between the detection outputs of these magnetic field detectors was determined. A magnetic flux detection method for a rotating electrical machine, characterized by: