JPH07308093A - Driving apparatus for variable-reluctance motor - Google Patents

Abstract

PURPOSE:To provide a variable-reluctance motor,that does not use a current sensor and thus makes possible the simplification of constitution and cost reduction, and that is further capable of high speed response. CONSTITUTION:When current passes through the exciting windings 15 of a variable-reluctance motor, it is detected by a resistor 14 for current detection. Then the detector voltage Va corresponding to the level of the current is output to the inverted input terminal of a comparator 19a. The comparator 19a compares the detection voltage Va with a reference voltage Vo, and outputs a detection signal S corresponding to the result of the comparison to a control circuit 21 through a photocoupler 20. The control circuit 21 controls current passing through the exciting windings : by adjusting the time to turn on a first IGBT 13 according the detection signal or doing the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for detecting a current flowing through an excitation winding in a drive device of a variable reluctance motor.

[0002]

2. Description of the Related Art Conventionally, when driving a three-phase or four-phase variable reluctance motor, the excitation winding of each phase is controlled independently. FIG. 2 is a block diagram showing an example of a driving device of this type of variable relaxation motor, in which 1 is an excitation winding of the motor, and 2a and 2b are insulation gate bipolar transistors (IG).
BT), 3a and 3b are switching element drive circuits. Here, when both the IGBTs 2a and 2b are turned on by the switching element drive circuits 3a and 3b, an energization path is formed from the positive side power source line 4a of the DC power source 4 through the excitation winding 1 to the negative side power source line 4b. As a result, a current I flows through the excitation winding 1.

The control circuit 5 is for controlling ON / OFF of the IGBTs 2a, 2b via the switching element drive circuits 3a, 3b, and by turning off the IGBT 2a, a circulating flow path from the exciting winding 1 to the circulating diode 6a. Is formed and the IGBT 2b is turned off to form a circulation flow path from the excitation winding 1 to the circulation diode 6b, and a current I ′ is passed through the excitation winding 1. The current sensor 7 is the coil 7
a, an iron core 7b, a Hall element 7c, and a detection circuit 7d (including a constant current circuit, an offset adjustment circuit, and an amplification circuit), and when a current flows through the coil 7a,
The iron core 7b is excited, and the Hall element 7c to the detection circuit 7d
The hall voltage is output to the detection circuit 7d and the detection voltage V
a is output.

The comparator 8 is a power source + V for the control circuit 5.
And 0V as a power source, the reference voltage Vo obtained by dividing the power source + V and 0V of the control circuit 5 is compared with the detection voltage Va from the detection circuit 7d, and the current detection signal S indicating the comparison result is compared. Output to the control circuit 5. Then, the control circuit 5 determines the IGBT 2 based on the current detection signal S.
The current flowing through the excitation winding 1 is controlled by controlling ON / OFF of a and 2b.

[0005]

However, the above-mentioned conventional device has the following problems because the current flowing through the exciting winding 1 is detected by the current sensor 7. The first is that the cost of the entire apparatus is increased because the configuration of the current sensor 7 is complicated and expensive. Secondly, it takes about 10 to 15 μs from the detection of the current by the current sensor 7 to the output of the current detection signal S, so that the quick response cannot be obtained. Therefore, when the motor is ground-faulted, it takes a considerable time from when the current sensor 7 detects the overcurrent to when the IGBTs 2a and 2b are turned off, and as a result, the IGBTs 2a and 2b may not be protected. . Therefore, it is considered that an overcurrent detection circuit 9 including a resistor and a comparator is provided, the overcurrent detection circuit 9 detects an overcurrent flowing through the negative power supply line 4b, and the IGBTs 2a and 2b are turned off based on the detection result. Has been. However, in this case, the cost of the device is further increased by the addition of the overcurrent detection circuit 9.

The present invention has been made in view of the above circumstances, and an object thereof is to eliminate the current sensor, thereby simplifying the structure and reducing the cost, and further, capable of high-speed response. A drive device for a motor is provided.

[0007]

A drive device for a variable reluctance motor according to the present invention is provided with a switching element provided in an energization path for supplying a DC power supply to an excitation winding of the variable reluctance motor and the energization path. The present invention is characterized in that the current detection resistor and the current detection means for detecting the current flowing through the exciting winding based on the voltage between the terminals of the current detection resistor are provided (claim 1).

In this case, the current detecting means is composed of a comparator circuit, and a switching element, a current detecting resistor and an exciting winding are connected in series in this order between the positive side power source line and the negative side power source line of the DC power source. Then, connecting the comparator circuit to a connection point between the current detection resistor and the excitation winding, and a switching element drive circuit for driving the switching element on and off, and a connection point between the switching element and the current detection resistor. And a freewheeling diode connected between the negative side power supply line of the DC power supply and the comparator circuit and the switching element drive circuit may be configured to be driven by a common power supply. 2). In addition, the reference voltage of the comparator circuit
It may be made from a power source for turning off the switching element (claim 3).

[0009]

According to the means described in claim 1, since the expensive current sensor having a complicated structure is eliminated and the current flowing through the exciting winding is detected by the current detecting resistor, the cost of the entire apparatus is reduced. Moreover, since the time from the detection of the current by the current detection resistor to the output of the detection voltage is accelerated,
The current detection resistor can also serve as the overcurrent detection circuit, which also contributes to cost reduction. Claim 2
According to the described means, since the comparator circuit and the switching element drive circuit are driven by the common power source, it is not necessary to separately provide a power source dedicated to the comparator circuit, and the cost can be further reduced. According to the means of claim 3,
Since the reference voltage of the comparator circuit is generated from the power supply for turning off the switching element, it is not necessary to separately provide a power supply for generating the reference voltage among the power supplies of the comparator circuit, and the cost can be further reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In this embodiment, the DC power supply 11 obtained by rectifying the AC power supply is smoothed by the smoothing capacitor 12 to drive the 3-phase or 4-phase variable relaxation motor. The device for performing the operation is provided in each of the excitation windings of each phase. That is, between the positive side power supply line 11a and the negative side power supply line 11b of the DC power supply 11,
First IGBT 13, current detecting resistor 14 and exciting winding 1
5 and the second IGBT 16 are connected in series in this order,
The first switching element drive circuit 17 is connected to the gate terminal and the emitter terminal of the first IGBT 13, and the second switching element drive circuit 18 is connected to the gate terminal and the emitter terminal of the second IGBT 16.

The current detecting resistor 14 detects the current flowing through the exciting winding 15, and is composed of a low resistance (= 0.1Ω) that does not hinder the energization of the exciting winding 15. The first IGBT 13 corresponds to the switching element according to claims 1 and 2, and has a collector terminal connected to the plus side power supply line 11a and an emitter terminal connected to one end of the current detection resistor 14. There is. The emitter terminal of the second IGBT 16 is connected to the minus side power supply line 11b, and the collector terminal thereof is connected to one end of the excitation winding 15.

The first switching element drive circuit 17 and the second switching element drive circuit 18 are the first IGBT.
T13 and the first IGBT 16 are turned on and off, and the first and second switching element drive circuits 17 and 18 are used to drive the first and second IGBTs.
When both 13 and 16 are turned on, a current I flows through the excitation winding 15 in a path extending from the “plus side power supply line 11a → current detection resistor 14 → excitation winding 15 → minus side power supply line 11b”.
(= 10A) flows. Incidentally, + VP (= + 15V),-
VP (= -5V) and 0VP are power supplies of the first switching element drive circuit 17, + VN (= + 15V), -VN (=
-5V), 0VN is the second switching element drive circuit 1
8 shows the power supply.

The inverting input terminal of the comparator 19a is connected to the connection point between the current detecting resistor 14 and the exciting winding 15. This comparator 19a includes resistors 19b and 1
9c and the comparator circuit 19 according to claim 2 (current detecting means according to claim 1).
Of the switching element driving circuit 17 of + VP and −
VP is used as a power supply, and the power supply −VP of the first switching element drive circuit 17 and the reference voltage Vo which is a divided voltage of 0VP are input to the non-inverting input terminal of the comparator 19.
a compares the detection voltage Va, which is the voltage between the terminals of the current detection resistor 14, with the reference voltage Vo, and outputs a detection signal S corresponding to the comparison result. Incidentally, the resistors 19b and 19c
Is for adjusting to “reference voltage Vo = voltage between terminals Va (= −1V)”.

A control circuit 21 is connected to the output terminal of the comparator 19a via a photocoupler 20. The control circuit 21 is mainly composed of a microcomputer, and the detection signal S of the comparator 19a is transmitted to the control circuit 21 through the photocoupler 20.
Moreover, the control circuit 21 is connected to the first switching element drive circuit 17 and the second switching element drive circuit 18 via the first photocoupler 22 and the second photocoupler 23, and the control circuit 21 is Drive control of the first and second switching element drive circuits 17 and 18 in accordance with the detection signal S of the comparator 19a,
Then, the second IGBTs 13 and 16 are driven on / off.

It should be noted that + V, 0V is a power supply for the control circuit 21, and the power supplies + V, 0V21 for the control circuit 21 and the power supplies + VP, -VP, 0V for the first switching element drive circuit 17 are used.
P and the power supply + V of the second switching element drive circuit 18
N, -VN and 0VN are insulated from each other. The anode of the photodiode 20a of the photocoupler 20 is connected to the power supply + VP of the first switching element drive circuit 17 via the resistor 20c, and the phototransistor 2
The emitter of 0b is connected to the power source 0V of the control circuit 21.

A first free-wheeling diode 24 is connected between the connection point between the emitter terminal of the first IGBT 13 and the current detecting resistor 14 and the negative side power supply line 11b of the DC power supply 11. The first freewheeling diode 24 corresponds to the freewheeling diode according to the second aspect of the present invention, and its cathode terminal is connected to the connection point and its anode terminal is connected to the negative side power supply line 11b. Also, the second I
The anode terminal of the second free-wheeling diode 25 is connected to the connection point between the collector terminal of the GBT 16 and the exciting winding 15, and the cathode terminal of the second free-wheeling diode 25 is connected to the positive power supply line 11a of the DC power supply 11. It is connected.

Next, the operation of the above configuration will be described. When a control signal is output from the control circuit 21, the first and second switching element drive circuits 1 are output based on the control signal.
7 and 18 operate, and the first and second IGBTs 13 and 16 are on / off controlled via the first and second switching element drive circuits 17 and 18. For example, when both the first and second IGBTs 13 and 16 are turned on, an energization path extending from "plus side power supply line 11a → current detecting resistor 14 → excitation winding 15 → minus side power supply line 11b" is formed. A current I flows through the excitation winding 15.

From this state, when the first IGBT 13 is turned off, "current detection resistor 14 → excitation winding 15 → first
When the second IGBT 16 is turned off, a circulation flow path extending from the freewheeling diode 24 to the current detecting resistor 14 ”is formed, and when the second IGBT 16 is turned off, the“ current detecting resistor 14 → excitation winding 15 → second freewheeling diode 25 → An annular flow path is formed to reach the current detecting resistor 14 ″, and the current I ′ flows through the exciting winding 15. In this way, the first and second IGBTs 13 and 16 are on / off controlled to control the current flowing through the excitation winding 15.

When a current flows through the exciting winding 15 in this way, first, the current detecting resistor 14 detects this current,
The comparator 1 detects the detected voltage Va according to the current level.
It outputs to the inverting input terminal of 9a. Next, comparator 1
9a compares the detection voltage Va with the reference voltage Vo and outputs a detection signal S corresponding to the comparison result to the control circuit 21 through the photocoupler 20. Then, the control circuit 21
Of the first and second IGBTs 1 based on the detection signal S
The excitation winding 15 is adjusted by adjusting the on-time of 3 and 16.
Control the current flowing through.

According to the above-described embodiment, the expensive current sensor having a complicated structure is eliminated and the current flowing through the exciting winding 15 is detected by the current detecting resistor 14, so that the cost of the entire apparatus is reduced. . Moreover, the current detection resistor 14
Since the time from detecting the current to outputting the detection voltage Va is accelerated, the current detecting resistor 14 detects the overcurrent to detect the first and second IGBTs 13 and 16.
Is turned off, the first and second IGBTs 13 and 1 are turned off.
6 can be sufficiently protected. As a result, the overcurrent detection circuit can be eliminated, and the cost can be reduced from this point as well.

By the way, in this embodiment, since the comparator circuit 19 side and the control circuit 21 side are insulated from each other, the power source + V and 0V of the control circuit 21 are supplied to the comparator circuit 19.
Can not be used for. However, there is a first I between the positive power line 11a and the negative power line 11b.
The GBT 13, the current detection resistor 14, and the excitation winding 15 are connected in series in this order, and the current detection resistor 14 and the excitation winding 1 are connected.
Since the comparator circuit 19 is connected to the connection point with 5, the power supply of the first switching element drive circuit 17 + V
It is possible to use P, -VP, 0VP for the comparator circuit 19, create a reference voltage Vo from the power supplies -VP and 0VP, and compare the reference voltage Vo with the detection voltage Va of the current detection resistor 14. become. As a result, there is no need to provide a dedicated power supply circuit for the comparator circuit 19, which can further reduce costs, and it is not necessary to separately provide a power supply for creating the reference voltage Vo among the dedicated power supplies for the comparator circuit 19, The cost can be further reduced.

In the above embodiment, the IGBT is used as the switching element, but the switching element is not limited to this. For example, a bipolar transistor or a MOSFE.
You may use T.

[0023]

As is apparent from the above description, the variable reluctance motor driving device of the present invention has the following excellent effects. According to the means of claim 1,
Since the expensive current sensor having a complicated structure is eliminated and the current is detected by the current detecting resistor, the cost of the entire apparatus is reduced. Moreover, since the current detection resistor can also serve as the overcurrent detection circuit, the overcurrent detection circuit is eliminated, and the cost can be reduced from this point as well.
According to the means described in claim 2, since the comparator circuit and the switching element drive circuit can be driven by the common power source, it is not necessary to separately provide a power source dedicated to the comparator circuit, and the cost can be further reduced. According to the means of claim 3, since the reference voltage of the comparator circuit is created from the power supply for turning off the switching element, it is not necessary to separately provide a power supply for creating the reference voltage among the power supplies dedicated to the comparator circuit. Further cost reduction can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

11 is a DC power supply, 11a is a plus side power supply line, 11b is a minus side power supply line, 13 is a first IGBT (switching element), 14 is a current detection resistor, 15 is an excitation winding, 17
Is a first switching element drive circuit, 19 is a comparator circuit (current detecting means), and 24 is a first freewheeling diode (freewheeling diode).

Claims (3)

[Claims] 1. A switching element provided in an energizing path for supplying DC power to an exciting winding of a variable reluctance motor, a current detecting resistor provided in the energizing path, and a terminal of the current detecting resistor. A drive device for a variable reluctance motor, comprising: current detection means for detecting a current flowing through the excitation winding based on an inter-voltage. 2. The current detecting means is composed of a comparator circuit, and a switching element, a current detecting resistor, and an exciting winding are connected in series in this order between the positive side power source line and the negative side power source line of the DC power source. A switching element drive circuit that connects the comparator circuit to a connection point between the current detection resistor and the excitation winding and drives the switching element on and off; and a connection point between the switching element and the current detection resistor. And a free-wheeling diode connected between the negative side power supply line of the DC power supply and the comparator circuit and the switching element drive circuit are driven by a common power supply. 1. The drive device of the variable reluctance motor according to 1. 3. The variable reluctance motor drive device according to claim 2, wherein the reference voltage of the comparator circuit is generated from a power source for turning off the switching element.