DE1942651A1 - Device for commutating the field coils of electric motors with electronic switches - Google Patents

Description

Lenco AG, Burgdorf (Switzerland)

Device for commutating the field coils of electric motors with electronic switches

The invention relates to a device for commutating the field coils of electric motors with electronic switches, which are controlled by high-frequency signals that are dependent on the rotor position.

In a known device of this type, the transmission takes place the high-frequency control signals from a common oscillator to the electronic switches via a high-frequency transformer with a central primary winding and secondary windings individually assigned to the switches. Included the magnetic coupling is established by an element rotating with the motor of the electric motor (e.g. a distributor finger made of ferrite) of the secondary windings changed cyclically with the primary winding. The disadvantage of this solution is that to achieve sufficiently high control signals a relatively high power must be expended and transmitted.

In another known device of this kind each electronic switch is assigned to a control-signal oscillator on and off by a dependent of the rotor rotation change of the damping of the resonant circuit or the feedback

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and is turned off. To operate this device is Although only a relatively small amount of power is required, the circuit is rather large without the effort involved.

Incidentally, both of the aforementioned embodiments have the disadvantage that the devices have relatively high interference signals in the Generate harmonic range.

The invention now shows a way, as the mentioned disadvantages of the known devices for high frequency control of Let electric motors improve. The device according to the invention is characterized in that the control signals for the electronic switches of these individually assigned, tuned to the frequency of a common high frequency © szillätors Resonant circuits are derived and that the resonant circuit coils in the area of influence of a rotating with the rotor, cyclically changing the inductance of the oscillating circuit coils Organ lie.

In the drawing, exemplary embodiments of the invention are shown, namely shows:

1 shows a basic circuit for the control signal generation j Fig. 2 and 3 an eohematiaoh illustrated arrangement for Inductance, change in oscillating circuit coils, in cross section and in view;

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Pig. 4 is a diagram showing the course of the voltage on Resonant circuit emerges as a function of the frequency and the detuning; ·

Pig · 5 Circuit of a high-frequency oscillator suitable for operating the devicej

Fig. 6, and 7 two different circuit options of the inventive device.

1 to 3, the principle of control signal generation is first explained in more detail using an example.

According to FIG. 1, a parallel resonant circuit consisting of the coil L and the capacitor 0 is connected via a series resistor R connected to a high-frequency oscillator, in the present case to a multivibrator M. The output signal of the The high-frequency oscillator can have any curve shape, but its frequency should be independent of fluctuations the supply voltage.

According to FIGS. 2 and 3, the resonant circuit coil L is equipped with a magnetic core K and is arranged in the area of influence of a magnetic yoke J fixed on the rotor shaft W of the electric motor to be controlled. Particularly advantageous is a segment-like configuration of the yoke J of FIG. 3 of the yoke 2 has proven "The central angle oC SiOH directed both to the number of the to be influenced, in the circle

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around the rotor shaft W arranged Sehwingkreisspulen or after Number of field coils of the electric motor to be commutated as well as the type of control of the electronic switches used for commutation

In Pig. 4 is the fixed base frequency of the multivibrator M (Pig. 1) denoted by fo. The oscillating circuit L, C is tuned to this frequency when the magnetic circuit of the Resonant circuit coil L is closed by yoke J «The inductance and the quality factor of the resonant circuit coil have in this state its maximum. When turning the yoke J im

to the
This state persists in the range of an angle of rotation corresponding to IZentriwinkel dl. However, as soon as the yoke J moves away from the coil core K, the inductance and the quality factor of the resonant circuit coil I decrease sharply. As a result, the oscillating circuit L, G is detuned; its new resonance frequency is denoted by f1 · If the oscillator frequency remains the same, the voltage on the resonant circuit therefore drops by the amount ^ U. This voltage jump is very steep and, depending on the quality and the arrangement of the resonant circuit coil, amounts to about 2Odb. This allows the control circuit of a switching transistor to be influenced very precisely.

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As a frequency-stable high-frequency oscillator, e.g. the Pig multivibrator. 5 application, the circuit of which is essentially known. Its frequency lets through Adjust the trim resistance T within narrow limits. The capacitor 01 increases the frequency stability at Supply voltage fluctuations. The output of the multivibrator is labeled A.

6 shows an exemplary embodiment of the commutation device for a direct current motor with three field coils F, which are connected at one end to the positive pole of the supply current source and whose other ends are designated u, ν and w. A switching transistor TS each connects this end u, ν or w of the relevant field coil F each with the negative pole of the supply current source.In the drawing, for the sake of simplicity, only one switching transistor IS is shown

One with the number of field coils? Corresponding number of parallel resonant circuits L ₁ C is via a series resistor E 1IMi in each case in a common preliminary stage with the transistor TV at the output A of the multivibrator according to FIG. 5 connected. At point χ of one oscillating circuit L, C, the high-frequency control signal can be taken, which is fed directly to the base of the floating transistor TS via a rectifier with the diode D and the Ctlättuogakondensator 02 in the form of a relatively high control current. In an analogous way they are

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Points y and ζ of the other parallel swing circles each with one of the switching transistors assigned to the remaining field coils F disturb connected (not shown)

Under certain circumstances the pre-stage (transistor TV) can be omitted also be connected to the negative line (Pig. 6). In the embodiment according to Pig. 6 the star point of the field coil group does not match that of the parallel resonant circuits so that an additional line to the motor is required.

In the embodiment according to FIG. 7, the parallel resonant circuits I, C are designed with high resistance and are connected to output A of the common multivibrator without a preliminary stage. Operation works and is preferably a silicon transistor · This amplifies the rectified control signal at the same time · Cx is the smoothing capacitor. Received that ·. Signal controls the finally Sohalttransistor TS rapidly y points by · Zwisohen and ▼ or · ζ and w is each the same as in Fig. 7 as circuit arrangement shown χ between the points and u '

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The gate part of the circuit arrangement according to FIG. 7 lies in the low control currents and the fact that the star points of the field coils and the parallel oscillating circuits are common. Am An electric motor with three field coils, for example, requires seven connecting conductors to the control electronics.

The commutation devices described also have the gate part that the low control currents are purely sinusoidal and thus completely free of harmonics, which is why no interference can occur in the higher frequency range. This is also one reason why the high-frequency oscillator does not necessarily need to generate a sinusoidal signal. The low costly voltage, which is, for example, about 2 T _ff in the case of resonance and about 0.2 T _ff in the case of tuning, means a further part of the proposed solution. The circuit st eolinis before effort is comparatively low

It goes without saying that instead of parallel oscillating circuits series resonant circuits can also be provided.

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Claims (9)

1942851 Pat exempt 1) Device for commutating the field coils of electrical motors with electronic switches that are controlled by high-frequency signals dependent on the rotor position, characterized in that the control signals for the electronic switches are derived from these individually assigned resonant circuits tuned to the frequency of a common high-frequency oscillator ψ and that the resonant circuit coils are in the area of influence of a with the rotor rotating, the inductance of the oscillating circuit coils are cyclically changing organ. 2. Apparatus according to claim 1, characterized in that each electronic switch has a parallel or Series resonant circuit is assigned, which has a series resistor connected to the common high-frequency oscillator! is closed. 3 «device according to claim 1, characterized in that that the high frequency oscillator is a multivibrator. 0 0 9 8 3 6/1031 • AD OWQiNAL 4 · Device according to claim 3, characterized in that the control electrodes of two amplifiers connected ala multivibrator elements for frequency stabilization via a capacitor are connected to each other. 5. Apparatus according to claim 1, characterized in that the resonant circuit coils with or without a ferromagnetic core are equipped and are in the area of influence of a ferromagnetic yoke rotating with the rotor 6. Apparatus according to claim 5, characterized in that the yoke is formed like a segment. 7 »Device according to claim 2, characterized in that each oscillating circuit has a rectifier with the base of a Switching transistor is connected. 8. The device according to claim l _t, characterized in that a transistor operating in C mode is used for rectification in an emitter circuit. 9. Apparatus according to claim 8, characterized in that a silicon transistor is used for rectification. BATH ORIGINAL - 9 - 009836/1031 Wed Blank page