SI9200102A - Electronic commutationed motor regulated with dc impulses - Google Patents

Abstract

An electronically commutated motor which is controlled by DC pulses is constructed in such a manner that it can be controlled by a cost-effective and simple electronic commutator which produces rectangular waveform control pulses by means of which the individual phases of the motor are switched on and off. This property of the motor is achieved by means of a special design of the salient poles 4, 4', 4'' for the individual phases, the centre angle tau of these salient poles 4, 4', 4'' being identical to one another, and also being identical for the magnetic poles 3 of the rotor 2. During operation of the motor, only one pole 4, 4', 4'' is always active, that is to say is excited via the excitation winding (energising winding) 6, 6', 6'', while in contrast the other pole which is associated with the same phase is passive and can be composed of a plurality of other salient poles or of passive pole segments 7, 7', 7'' whose planes of symmetry are directed radially from the stator 1 in the direction of the rotor 2. The common width of this passive pole is in this case a multiple of the centre angle. <IMAGE>

Description

Electronically switched motor controlled by DC pulses

The invention belongs to the field of construction of electrical machines with electronic switching and is classified in class H 02K 29/00 by MKP.

Electronically switched machines are synchronous machines equipped with magnetic sensors that sense the rotor position and control individual stator winding phases, so that those stator windings are always excited, which, given the current rotor position, cause maximum momentum on the moto shaft.

The induced voltage of a known synchronous machine is alternating, and its time course is usually sine. Therefore, the electronic commutator must generate alternating voltage with a sine-wave path in order to be able to supply electrical power to the phase windings of the electronically switched machine. The basic functions of the electronic commutator are to determine the rotor position, to generate alternating voltage, that is, to rotate at such a frequency that corresponds to the current speed of rotation of the rotor, and to distribute electricity to individual phase windings depending on the current rotor position. Additional features of the electronic commutator include limitation and control of electric current, regulation of engine speed, motor protection and more.

In order to achieve good machine efficiency, the electronic commutator must be well adapted to the characteristics of the motor, since any difference between the shape, that is, the timing of the induced moto voltage and the shape of the supply voltage generated by the electronic commutator, changes to a loss.

The technical problem of electronically commutated motors, which are becoming increasingly popular due to their high specific power and long life, is an engine design that will make it possible to use a simple and inexpensive electronic commutator while maintaining good engine efficiency.

The solution to the technical problem will be described in more detail below and shown in the drawings showing:

FIG. 1 is a cross-section through a single-phase synchronous machine with a flow diagram of the induced voltage of a rectangular shape; 2 is a cross-sectional view through a single-phase embodiment of the synchronous machine according to the invention with a flow diagram of the induced rectangular voltage of FIG. 3 is a cross-sectional view through a three-phase embodiment of the synchronous machine according to the invention; 4 is a single-phase circuit diagram of an electronic commutator of the invention.

The simplest electronic switch that can be built contains - for powering each phase, the rotor position sensor, electronic phase switch on and off, current limiter and surge limiter that occurs when the phase is switched off.

Such a simplest electronic commutator can generate rectangular electrical current pulses for each phase. In order to control the motor with a defined direction of rotation with this commutator, the motor must be designed in such a way that the rectangular voltage is induced (that the time of the induced voltage is rectangular), that the motor is designed in two- or multiphase design and that the motor is faultless operate with half-wave power.

A single-phase embodiment of a synchronous machine whose induced voltage is of rectangular shape is shown schematically in FIG. 1. Such a machine has a stator 1 on which an excitation coil 6 is mounted, while two permanent magnets 3 of alternating polarity are mounted on the rotor 2. It is known that the conditions for attaining the rectangular shape of the induced voltage are as follows: the density of the magnetic field in the air gap must be constant, the poles must be expressed, and the width of the pole must be equal to the half division t. As can be seen from Figure 1, however, under these conditions, only two poles 4 can be fitted to the machine, that is, one half pair. Or in other words: the machine can only be manufactured in a single-phase version. In order to produce a machine with a defined direction of rotation, that is, in order to produce a multiphase machine with pronounced poles, it is essential to obtain space at the circumference of stator 1. Therefore, let us investigate what happens if the width of the stator pole is a multiple of half division.

Figure 2 schematically shows a single-phase synchronous machine consisting of stator 1 and rotor 2. Four permanent magnets of 3 alternating polarity are mounted on rotor 2. Stator 1 is provided with two poles 4 and 5. The upper pole 4 has a rotor pole width t, while the lower pole 5 has a pole width 3t. We equip the upper pole 4 with an excitation winding 6 and call it the active pole, while pole 5 is not excited and it is called the passive pole. If the machine according to Fig. 2 is connected to a voltage, it is found that it behaves similarly to the machine according to Fig. 1. The time course of the induced voltage of the machine according to Fig. 2 is equal to the time course of the induced voltage of the machine according to Fig. 1. Both runs of the induced voltage are rectangular. Alternatively, windings of other phases can be installed in the space occupied by the passive pole, which is excited when winding 6 is not excited.

The most appropriate number of phases of the machine according to the invention is selected according to the requirement that the machine must be operated with half-wave excitation. For three-wave excitation, a three-phase system is preferred, in which the second and third phases represent the negative first-phase waves.

3 is a three-phase embodiment of the machine according to the invention. The machine consists of a stator 1 and a rotor 2 and, of course, other standard engine parts, such as a housing, bearings, a shaft and other known machine elements, are not shown. Four permanent magnets of 3 alternating polarity are mounted on rotor 2. Stator 1 is equipped with three pronounced poles 4, 4 ', 4, which have a pole width τ (equal to half division) and are equipped with windings 6, 6', 6. Stator 1 therefore has three active poles. If a single active pole 4 of width t is excited, then the rest of the stator 1 of width (2ir-r) represents an active passive 4 having a pole width of 3t and consisting of several partial half segments 4 ', 4, 7. 7 ', 7. We have obtained a three-phase motor, which will have the following characteristics in that the motor will function smoothly if the individual phase windings are fed in sequence by direct current pulses of electricity, with the direction of rotation being divided by the order of excitation of the individual phases. The induced voltage in the individual phase windings, however, has a rectangular time course.

In order to control the electronic commutator, magnetic sensors 8, 8 ', 8 must also be installed in the motor above the rotor and rotated by an angle of β equal to 90 degrees of the electric angle from the pole of the pole that the individual sensor controls.

This gives us a machine whose electronic control is as easy as possible. The circuit of this control can be seen in Figure 4.

The magnetic sensor MS switches on the transistor T _{p the} transistor turns on the transistor T ₂ . Both transistors act as switches to minimize losses. The maximum current (motor starting current) of transistor T ₂ can be limited by limiting the voltage of the base of transistor T ₂ . This task is performed by Zener diode Z. Diode D _x raises the emitter potential of transistor T _p to close it completely when needed. Diodes D ₂ and D ₃ present electrical connection to the previous phase at terminal I and the next phase at terminal II with the task of switching off the previous phase without switching on the magnetic sensor signal when the particular phase is switched on. This eliminates the concealment of switching on two phases.

To eliminate the overvoltage peaks that occur when the individual phase is switched off, equip individual poles with auxiliary winding 9, 9 ', 9 and connect it to the voltage counter with winding 6, 6', 6 by means of diode D ₄ , as shown in wiring diagrams Fig. 4. When phase winding 6 is switched off, voltage is also induced in the auxiliary winding 9. The energy accumulated in the pole inductance is returned to the grid by the auxiliary winding 9, 9 ', 9 and diode D ₄ , while the induced voltage in the negative pole is not sufficient to drive the short-circuit current after the auxiliary winding 9, 9 ', 9.

Claims (4)

Electronically commutated, single-impulse-controlled motor, characterized in that at least four magnetic poles (3) are fixed at the periphery of the rotor (2) and protrude from the stator (1) radially against the rotor (2) by at least three expressed poles ( 4, 4 ', 4) and in symmetry between the expressed poles (4, 4', 4) of at least three passive pole segments (7, 7 ', 7), with the magnetic poles (3) having the same center angle (r) , which is at the same time the same for all the expressed poles (4, 4 ', 4) and on all the expressed poles (4, 4,', 4) both phase windings (6,6 ', 6) and auxiliary windings are installed (9.9 ', 9). Motor according to claim 1, characterized in that the magnetic poles (3) are permanent magnets. Motor according to claim 1, characterized in that the magnetic poles (3) are electromagnetic. Motor according to claim 1, characterized in that the magnetic sensors (8,8 ', 8) are fixed in rotational direction at one end of the poles (4, 4', 4).