JPH0469093A - Motor current controller - Google Patents

Abstract

PURPOSE:To decrease the effect of offset drift by winding coils, through which currents corresponding to current command values are passed, in opposite directions around the same magnetic core, detecting deviations of excitation current values from the current command values with Hall elements arranged in the gaps of the magnetic core, and controlling the excitation currents by feedback based on the deviations. CONSTITUTION:Current command values VINA and VINB are transmitted to current exchangers 101 and 102, converted into currents IINA and IINB, and passed through coils 111 and 112. Excitation currents IOUTA and IOUTB are passed through coils 31 and 32 Hall elements 41 and 42 detect deviations of the excitation current values from the current command values based on magnetic fields generated in magnetic cores 21 and 22 and supply the deviations VDIFA and VDIFB to a drive circuit 9. The drive circuit 9 transmits excitation voltages VA', VB', and VC' proportional to the values of the deviation signals VDIFA and VDIFB and the excitation voltages supply the excitation currents IOUTA, IOUTB, and IOUTC to the coils of each of the phases of a motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a motor current control device that performs feedback control of an excitation current supplied to a motor coil.

<Prior Art> Conventionally, as such a motor current control device, there is one shown in FIG. 2, for example.

In the figure, 1 is a motor, and in the example, it is a three-phase motor,
2. and 22 are gaps 21. and 212 are provided on the magnetic core, and 31 and 32 are wound around the magnetic cores 21 and 22, and the motor 1
excitation of the coil, 4. and 42
is gap 21. and 5. a Hall element disposed within 212 for magnetically detecting the magnitude of the excitation current; and 52 are Hall interface sections (hereinafter, the interface will be abbreviated as I/F) that receive detection signals from the Hall elements and generate a current proportional to the excitation current.

6, and 62 are the hall I/F section 5. and an amplifier that amplifies the output of 52;7. and 72 are current command values VINA and VINB given to the first and second phase coils, and amplifiers 61 and 6.
2 is a subtracter that takes the deviation of the output value; 8 is a subtracter 7. and 7□
This is an adder that calculates the current command value of the third phase coil by adding the deviations obtained by inverting their signs. The current command values given to the first-phase and second-phase coils are values of sine wave signals whose phases differ by 120° from each other.

9 is a drive circuit, and subtracter 7. 72 and the adder 8 to generate an excitation voltage according to the current command value determined by the adder 8
An excitation current is supplied to 1 and 32.

The drive circuit 9 is constructed by combining a PWM circuit, a photocoupler, and a bridge circuit, and its specific construction is shown in FIG. 3, for example.

In such a control device, the current command value of the sine wave signal and
The excitation current supplied to the motor 1 is feedback-controlled based on the deviation of the detected value of the Hall element.

<Problems to be Solved by the Invention> However, in such a control device, an offset also occurs in the excitation current due to temperature drift of the offset of the Hall element. This offset causes torque ripple in the motor, deteriorating control characteristics and generating noise.

The present invention has been made to solve these problems, and it is an object of the present invention to realize a motor current control device in which the influence of offset drift of a Hall element used to detect excitation current is reduced.

Means for Solving the Problems> The present invention provides a motor current control device that performs feedback control of excitation B and current supplied to the coils of a motor. a first coil through which a current flows; a second coil which is wound around this magnetic core and whose winding direction is opposite to that of the first coil, through which a current according to a flow command value flows; a Hall element arranged to detect a deviation between the excitation current value and the current command value; and a drive that generates an excitation voltage according to the detected deviation of the Hall element and supplies an excitation current to the first coil. A motor current control device characterized by comprising a circuit.

In the present invention, a coil through which an excitation current flows and a coil through which a current according to a current command value flows are wound around the same magnetic core with the winding directions reversed, and the current command is determined by a Hall element placed in the gap between the magnetic cores. Detects the deviation between the value and the value of the excitation current,
The excitation current is feedback-controlled based on this deviation.

<Example> Hereinafter, the present invention will be explained using the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention. Components in FIG. 1 that are the same as those in FIG. 2 are given the same reference numerals.

In Figure 1, 10. and 102 are current converters that convert current command values VINA and VINB given by voltage signals into current signals l2NA and IINB proportional to the voltage values; 11. and 1
12 is wound around magnetic cores 21 and 22 and receives a current signal IXNA.
This is a coil excited by I□NB. coil 11
The winding directions of coils 1, 112 and 31, 32 are opposite to each other.

As a result, the coils 111 and 112 become the coil 3+,
Generates magnetic flux that cancels out the generated magnetic flux of 32.

The operation of the device configured in this way will be explained.

The $ flow command values VINA and VINB are sent to the current converter 10.
+ , given to 102, current II NA , II N
Convert to B and send to coil 11+, l12, coil 3+
, 32, excitation currents l0tlTA and l0UTEI flow through them.

The Hall elements 4+, 42 detect the deviation between the excitation current value and the command current value based on the magnetic field generated by the magnetic cores 2+, 22, and the deviations v, XFA, v, IFB are sent to the drive circuit 9.
give to

The drive circuit 9 outputs excitation voltages VA', Va', and Vc proportional to the values of the deviation signals VDIFA and VDIFB, and these excitation voltages cause excitation currents I OUT A and I O
U T B + I OUT C is applied to the coils of each phase of the motor 1 .

Here, focusing only on the first phase, the magnetic core 2. gap 21. The magnetic flux density BA is given by the following equation.

BA= (μ/l)
・ IOU D A) μ: Gap 21
Permeability of 1! :Magnetic core 2. Magnetic path length N2: Coil 11. As a result, the deviation signal VD:[FA becomes as follows.

VorFA=fi-BA+ΔV 1′　X　　(N2　・　IINA Nl　°　IO[JTA] +ΔV N1: Number of turns of coil 31 Δv: Offset of deviation signal A: Gain of Hall element 1'-1・(μ/l) The output VA' of the drive circuit 9 is given by the following equation.

VA ′”G-Vo 11: A = G・i′X (N2・Ix Nh-N,
-10UTA) 10V) G: Gain of drive circuit 9 Therefore, excitation current l0UTA is given by the following equation.

1ouv A = VA ′,”z = (G/Z) ・ (1′ X (N2 ・
lx NAN+ ・l0UTA) +Δ
V)...■ Z: Coil 3. Solving the impedance 0 equation for l0UTA yields the following.

In equation (2), if N, -1'-G>Z, IINAVINA, then the following equation holds true.

1ouvA=(N2/N+)-a-VzNA・・■a・+(1/N,・A′)・ΔV
... ■a: Gain of current converter 101 In the equation (2), the influence of ΔV can be reduced by increasing N and N2.

On the other hand, in the control device shown in FIG. 2, the excitation current 10UT given to the coil of the motor is given by the following equation.

Iouv = (1/b-N-11) ・VI N+(
1/N -A,) ・Δ■...■N: Coil 3.
Number of turns VI N: Current command value b: Amplifier 6+, gain of 62, -(μ/I) A2: Hall I/F section 5+, gain of 52 In the formula, by increasing the number of turns N, ΔV However, N is limited by the saturation magnetic flux of the Hall element.Therefore, the influence of 8V cannot be reduced.

The same applies to the second phase coil.

According to the present invention, since the excitation current is given by the formula (2), by increasing the number of turns of the coil, the offset 8V
term can be removed. This makes it possible to eliminate the influence of temperature drift on the offset of the Hall element.

In addition, when the term of offset ΔV is removed from formula (■), the proportional constants between the excitation current l0UTA and the current command value VINA are only N 2 / N + and a, so it is not affected by the gain fluctuation of the Hall element. , thereby obtaining a sinusoidal excitation current with stable amplitude.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a diagram showing an example of the structure of a conventional motor current control device, and Fig. 3 is a specific block diagram of a part of the device shown in Fig. 2. It is. 1...Motor, 2+, 22...Magnetic core, 21121
2... Gap, 3+, 32.11+, 112・
...Coil, 4+, 42...Hall element, 9...
Drive circuit, 10+...Current converter.

Claims (1)

[Claims] A motor current control device that performs feedback control of an excitation current supplied to a motor coil, comprising: a magnetic core provided with a gap; a first coil wound around the magnetic core through which an excitation current flows; , a second coil which is wound around the magnetic core and has a winding direction opposite to that of the first coil, through which a current according to the current command value flows; and a second coil which is disposed within the gap and has an excitation current value. and a Hall element that detects a deviation between the current command value and a drive circuit that generates an excitation voltage according to the detected deviation of the Hall element and supplies an excitation current to the first coil. Motor current control device.