KR20160097645A - Brushless direct current motor type inverter driving circuit - Google Patents

Abstract

The present invention relates to an inverter driving circuit for a brushless direct current (BLDC) motor, capable of preventing the reduction of a power factor due to motor inductance through three power factor compensation capacitors by connecting each power factor compensation capacitor on a three-phase winding in an output terminal of an inverter which receives DC power and applies three-phase AC power to the BLDC motor with a three-phase wiring structure in parallel. According to the present invention, the inverter driving circuit for a BLDC motor comprises: a motor part which has a winding with a three-phase coil generating an inductance element; an inverter part which has each switching element connected to the three-phase winding; the power factor compensation capacitor which is connected to a connection line between the inverter part and the three-phase winding in parallel; a power supply part which supplies power to the inverter part; an inverter driving part which switches an on-operation or an off-operation of each power switching element in the inverter part; and a control part which applies a switching driving signal of each power switching element to the inverter driving part.

Description

[0001] The present invention relates to an inverter driving circuit for a brushless DC motor,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter driving circuit for a brushless direct current motor, and more particularly, to a brushless direct current (BLDC) motor having a three- A brushless direct current motor inverter for preventing the phenomenon of reduction of the power factor due to the motor inductance through three power factor compensating capacitors by connecting the power factor compensating capacitors in parallel to the three phase windings at the output of the inverter Driving circuit.

In general, brushless direct current (BLDC) motors are increasingly used in applications where there is no risk of sparks or arcs generated by brushes or commutator segments. In addition, BLDC motors are often installed where constant speed operation is required.

The BLDC motor consists of permanent magnet field rotors and stator armature windings excited by electronic switching. The rotation of the armature magnetic field is obtained by changing the current direction of the armature winding using a power transistor.

A position sensor is attached to the rotor shaft so that it can be switched at an appropriate time in order to add synchronism between the permanent magnet magnetic field of the rotor and the rotor system of the faulty armature. In addition, the position of the rotor may be detected by sensing the voltage induced in the stator armature winding without using a position sensor.

1 is a diagram showing a drive inverter circuit of a conventional BLDC motor.

As shown in FIG. 1, the BLDC motor has a three-phase wiring structure. The inverter is composed of six power switches. The inverter applies a three-phase AC power to the motor by receiving a direct current (DC) power.

The power required to make the output of the motor is the active power, and the reactive power deteriorates the power factor of the inverter of the motor. The power factor is determined by the ratio of the active power to the apparent power as calculated by dividing the active power by the apparent power.

Generally, the power factor of a motor inverter is about 95%, but if the motor has a very large inductance, the power factor may fall below 85%. When a voltage is supplied to the motor, the input power is multiplied by the counter electromotive force and the current to form an output, which is constituted by the coil loss in the motor coil and the inductive load due to the inductance.

When a current is applied to a motor in which a coil is wound, a magnetizing inductance is present, and a voltage drop occurs due to the inductance component. In particular, as the inductance becomes larger, the inductive load of the motor increases, resulting in a large reactive power, and the power factor of the inverter is lowered due to the increased ineffective component. Due to the increase of the power factor of such an inverter, the phase current for generating the same output in the inverter is increased to increase the loss of the inverter, resulting in a problem that the efficiency of the inverter and the motor is lowered.

Korean Registered Patent No. 177948 (registered on November 19, 1998)

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to solve the above problems in the prior art. According to an aspect of the present invention, there is provided a three phase AC power source, The present invention provides an inverter drive circuit for a brushless direct current motor, wherein the power factor compensating capacitors are connected in parallel to the windings to prevent the power factor due to motor inductance from being reduced through three power factor compensating capacitors.

According to an aspect of the present invention, there is provided an inverter drive circuit for a brushless DC motor, including: a motor section having a winding having three phases for generating an inductance component; An inverter unit connected to each of the power switching elements in the three-phase winding; A power factor compensating capacitor connected in parallel to a connection line between the inverter unit and the three phase windings; A power supply unit for supplying power to the inverter unit; An inverter driving unit for switching on and off operations of power switching elements in the inverter unit; And a control unit for applying a switching driving signal of each power switching element to the inverter driving unit.

The power factor compensating capacitor may be connected between the V phase and the W phase, and between the W phase and the U phase, respectively, in parallel between the U phase and the V phase of the three phases at the output terminal of the inverter section.

In addition, the capacity of the power factor compensating capacitor may be set to be the same as the magnitude of the inductance component of the motor unit.

In addition, the three power factor compensating capacitors may have the same capacity size.

The capacity magnitudes of the three power factor compensating capacitors may be set to have the same magnitude of the apparent power and the magnitude of the active power.

According to the present invention, the power factor reduction phenomenon depending on the inductance component of the motor unit can be remarkably reduced by the power factor compensating capacitor, and the power factor of the motor and the inverter is improved, and the magnitude of the current flowing to the motor and the inverter is reduced. Therefore, the resistance loss in the inverter and the motor is reduced, and the efficiency of the motor is improved. The inverter has an inherent power factor and the efficiency is reduced due to the current rise due to the increase of the reactive power in the inverter.

1 is a diagram showing a drive inverter circuit of a conventional BLDC motor.
2 is a block diagram showing an inverter driving circuit for a brushless DC motor according to an embodiment of the present invention.
3 is a diagram showing an example of a further configuration of an inverter driving circuit for a brushless DC motor according to an embodiment of the present invention.
4 is a diagram showing an example in which general apparent power is represented by active power and reactive power.
5 is a diagram showing an example in which active power according to an embodiment of the present invention is expressed by apparent power.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, the same reference numerals will be used for the same constituent elements in the drawings, and redundant explanations for the same constituent elements will be omitted.

2 is a block diagram showing an inverter driving circuit for a brushless DC motor according to an embodiment of the present invention.

2, an inverter drive circuit 200 for a brushless DC motor according to the present invention includes a motor unit 210, an inverter unit 220, and a power factor compensating capacitor 230.

The motor unit 210 has windings having three-phase coils for generating inductance components. Here, the motor unit 210 includes a BLDC motor and is supplied with power and provides rotational force. In other words, a BLDC motor is a structure in which there is no insulation conductor such as a carbon brush for transmitting electric power, a motor is provided in a motor shaft, a coil is provided on the inner wall surface of the motor case, The brushes are not needed as they are supplied to the wall-mounted coils.

The inverter unit 220 is connected to the power switching elements S1 to S6 for the three-phase (U, V, W) windings.

The power factor compensating capacitor 230 is connected in parallel on the connection line between the inverter unit 220 and the three-phase windings of the motor unit 210.

Also, the power factor compensating capacitor 230 can be connected in parallel between the V phase and the W phase, between the W phase and the U phase, between the U phase and the V phase in the three phases at the output terminal of the inverter unit 220 .

Also, the magnitude of the capacity factor of the power factor compensating capacitor 230 may be set to be the same as the magnitude of the inductance component of the motor unit 210.

Further, each of the three power factor compensating capacitors C1 to C3 may have the same capacity size.

The capacity magnitudes for the three power factor compensating capacitors C1 to C3 can be set so that the magnitude of the apparent power and the magnitude of the active power have the same magnitude.

The inverter driving circuit 200 for a brushless DC motor according to the embodiment of the present invention includes a motor unit 210, an inverter unit 220 and a power factor compensating capacitor 230, The power supply unit 240, the inverter driving unit 250, the control unit 260, and the rotor position detection unit 270 may be further included. 3 is a diagram showing an example of a further configuration of an inverter driving circuit for a brushless DC motor according to an embodiment of the present invention.

The power supply unit 240 supplies power to the inverter unit 220. That is, the power supply unit 240 supplies the driving power to the inverter unit 220, the inverter driving unit 250, and the control unit 260 with the DC power source by transforming the AC power to the voltage V _dc .

The inverter driving unit 250 switches ON or OFF operations of the power switching elements S1 to S6 in the inverter unit 220. [

The control unit 260 applies the switching driving signals of the power switching elements S1 to S6 to the inverter driving unit 250. [ That is, the control unit 260 controls the switching operation of the switching elements S1 to S6 of the inverter unit 220 according to the user's operation to control the starting, operation, and speed of the motor unit 210, Generates a switching driving signal for switching each of the switching elements S1 to S6 according to the output of the position detecting unit 270 and applies the switching driving signal to the inverter driving unit 250. [

The rotor position detection unit 270 senses the voltage induced in each phase coil of the motor unit 210 and detects the rotor position.

The inverter driving circuit 200 for a brushless DC motor according to the present invention configured as described above transforms and rectifies an AC power source at a power supply unit 240 so that the inverter unit 220 and the inverter driving unit 250, (260).

Here, the power supply unit 240 may include a filter unit and a rectifying unit although not shown in the figure. The rectifying unit rectifies the AC power inputted through the filter unit and supplies the DC power to the inverter unit 220, the inverter driving unit 250, and the control unit 250. In addition, (260).

At this time, the DC voltage V _dc applied to the inverter unit 220 can be expressed by the following equation (1).

Therefore, the input power (P _in ) can be expressed as a product of the counter electromotive force and the current as shown in the following Equation (2).

That is, the input power (P _in ) is constituted by the copper loss in the three-phase winding coil of the motor unit 210 and the inductive load caused by the inductance component.

At this time, the active power can be expressed by the apparent power and the reactive power as shown in FIG. That is, the effective power can be calculated as a square root of a value obtained by subtracting the square of the reactive power from the square of the apparent power according to the following equation (3). 4 is a diagram showing an example in which general apparent power is represented by active power and reactive power.

However, in order to reduce the power factor due to the increase of the inductive load due to the inductance generated in the motor unit 210, three (C1, C2, C3) power factor compensation capacitors ( 230 are connected in parallel, the inductive load is canceled by the power factor compensating capacitor 230 according to the following equation (4). Therefore, the effective power can be represented by apparent power without reactive power as shown in Fig. 5 is a diagram showing an example in which active power according to an embodiment of the present invention is expressed by apparent power.

At this time, the size C of the power factor compensating capacitor 230 is set to be the same as the magnitude of the inductance in the motor unit 210.

For example, when the effective power is 80 kW, the reactive power is 60 kW, and the apparent power is 100 kVA, the power factor correction factor is 80/100 = 0.8 (cos? As the capacity of the capacitor 230 becomes 33.7 kVAR, the effective power is changed to 95 kW, and the power factor after improvement is 95/100 = 0.95 (cos? 2).

Here, the capacity Qc of the power factor compensating capacitor 230 required for the improvement can be set according to the following equation (5).

The inverter driving unit 250 transmits the switching driving signal output from the control unit 260 to each of the switching elements S1, S2, S3, S4, S5, and S6 of the inverter unit 220, S2, S3, S4, S5, and S6. At this time, although not shown, the inverter driving unit 250 can be constructed of, for example, a general-purpose photocoupler (PC1) and a high-speed switching photocoupler (PC2). Here, the operation of driving the switching elements S1 and S2 of the U-phase is described as an example, and the operation of driving the remaining V- and W-phase switching elements S3, S4, S5, and S6 is also the same. The general-purpose photocoupler PC1 outputs a switching drive signal for switching the low-frequency output from the control unit 260, that is, a switching drive signal for phase-switching, to the base of the first switching device S1 So that the first switching device S1 performs a switching operation to perform phase switching. The high-speed switching photocoupler PC2 receives the high-frequency switching driving signal, that is, the pulse width modulation signal, output from the controller 260 by optical coupling in the high-speed switching photocoupler PC2, And supplies the power to the stator armature winding of the motor unit 210 by switching the second switching element S2 by transmitting the voltage to the base end of the stator arm S2.

As described above, the inverter driving circuit 200 for a brushless DC motor according to the present invention supplies a pulse width modulation signal as a switching driving signal to either the upper switching element of the inverter unit 220 or the lower switching element Speed switching of the switching unit to supply power to the motor unit 210 to operate the motor unit 210. At this time, by changing the pulse width of the pulse width modulation signal, the start and speed of the motor unit 210 are controlled can do.

As described above, according to the present invention, a three-phase AC power source is supplied to a three-phase brushless direct current (BLDC) motor having a three- And the capacitors are connected in parallel to each other, thereby realizing an inverter drive circuit for a brushless DC motor that can prevent the phenomenon of reduction of the power factor due to the motor inductance through three power factor compensating capacitors.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. Only. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

The present invention relates to a method of driving a three-phase brushless direct current (BLDC) motor having a three-phase wiring structure by connecting a three-phase AC power source to a three-phase winding of an inverter, The present invention can be applied to an inverter drive circuit for a brushless DC motor which can prevent the phenomenon of reduction of the power factor due to motor inductance through three power factor compensating capacitors.

200: Inverter drive circuit for brushless DC motor
210:
220:
230: Power Factor Correction Capacitor
240: Power supply
250:
260:
270: Rotor position detection section

Claims (5)

A motor section having a winding with three coils for generating an inductance component;
An inverter unit connected to each of the power switching elements in the three-phase winding;
A power factor compensating capacitor connected in parallel to a connection line between the inverter unit and the three phase windings;
A power supply unit for supplying power to the inverter unit;
An inverter driving unit for switching on and off operations of power switching elements in the inverter unit; And
A controller for applying a switching driving signal of each power switching element to the inverter driving unit;
And an inverter drive circuit for a brushless DC motor.
The method according to claim 1,
Wherein the power factor compensating capacitor is connected between a V-phase and a W-phase, and between a W-phase and a U-phase between the U-phase and the V-phase of the three phases at the output terminal of the inverter section, Inverter drive circuit.
The method according to claim 1,
Wherein the capacity of the power factor compensating capacitor is set to be equal to the magnitude of the inductance component of the motor unit.
The method according to claim 1,
Wherein the three power factor compensating capacitors each have the same capacity size.
The method according to claim 1,
Wherein the capacity magnitudes of the three power factor compensating capacitors are set so that magnitudes of the apparent power and the magnitudes of the active power are the same.

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