KR101253232B1 - Device For Preheating Compressor And Method Thereof - Google Patents

Abstract

Disclosed is a preheating device of an inverter compressor and a method thereof for preheating the inverter compressor at a low outdoor temperature.

The present invention outputs a control signal for high frequency switching of the upstream switching element to preheat the compressor, and at the same time outputs a control signal for low frequency switching of the downstream switching element, and the motor current flows in each preset unit section. It includes a control circuit for changing.

According to the present invention, since the flow of the motor current is alternated, it is possible to prevent deterioration of the motor coil and to control heating with high efficiency. In addition, since the upstream switching element is always switched to a high frequency PWM signal, the charging operation in the bootstrap circuit can be performed stably, and the positioning of the rotor by the low motor current is performed, followed by preheating by increasing the motor current, resulting in low noise. Can be planned.

Description

Device preheating compressor and method thereof

1 is a view showing a control signal output to the switching element according to the conventional method of preheating the compressor.

2 is a view showing a control signal in the case of changing the phase of the current flowing in the motor according to the conventional method of preheating the compressor.

3 is a view showing the configuration of an inverter circuit applied to the present invention.

4 is a diagram showing the configuration of a control circuit for applying control power to an upstream switching element according to the present invention.

5 is an energization pattern in the case where both sides are alternately chopped with respect to the upstream switching element and the downstream switching element constituting the inverter circuit.

FIG. 6 is a current conduction pattern according to the present invention as compared with FIG. 5 in the case of chopping the upstream switching element constituting the inverter circuit.

FIG. 7 is a diagram illustrating a control signal applied to an upstream switching element and a downstream switching element according to the energization pattern of FIG. 6.

8A to 8F are diagrams showing paths of motor current corresponding to respective cases of changing the phase of the current flowing in the motor in FIG. 7.

FIG. 9 is a diagram illustrating a current induced in a motor in response to each case of changing a phase of a current flowing in the motor in FIG. 7.

Description of the Related Art [0002]

100: inverter circuit

110: three-phase motor

200: control circuit

The present invention relates to a preheating device and a method of the inverter compressor for preheating the inverter compressor in a state of low outdoor temperature, and more particularly, to prevent the deterioration of the coil and to perform high-efficiency heating control and to reduce noise. The present invention relates to a compressor preheating device and a method thereof.

The compressor used in the heat pump type air conditioner preheats and controls the three-phase motor through the inverter circuit.

Preheating control of the compressor is performed for the purpose of improving heating performance and improving the reliability of the compressor at low temperatures.

The method for preheating the compressor includes a method of using a crank-case heater of the compressor and heating a current by applying a current to the coil of the motor.

When using a method of applying a current to the motor coil, care must be taken to prevent deterioration of the coil, high efficiency heating control, and low noise.

A general method for preventing the deterioration of the motor coil is to change the phase of the motor coil through which the current flows at a predetermined time, and a general method for efficiently heating and controlling the compressor is to intermittently supply current to the motor coil. To give. Such a typical example is the "motor control apparatus" of Japanese Patent No. 2804796.

In this " motor control device ", a motor control device having an inverter circuit composed of a motor and a plurality of switching elements, wherein a diode is connected to each of the plurality of switching elements in parallel, and at the same time, the switching element of the current path upstream of one coil is connected. Select on / off control (see 54 in FIG. 1), turn on the rest of the switching elements (see 55, 56 in FIG. 1), and return the electron energy of the motor coil when the upstream switching element described above is off. A first mode in which a reflux current is supplied to the motor through a diode and classifies this continuously flowing current from one coil of the motor to another coil, and a low frequency other switching element while flowing a current through the motor according to the first mode. 2nd mode which turns on / off, the motor current is controlled by alternately repeating this 1st mode and a 2nd mode (refer 91, 92, 93 of FIG. 2).

The "motor control apparatus" configured in this way allows the motor current to flow intermittently and can perform preheating control with good efficiency.

In Fig. 1, a method of intermittently flowing a motor current is shown. In the period of T3, the switching element is turned on to flow the motor current. In the period of T3 to T4, all the switching elements are turned off to cut off the motor current. Increasing the peak value of the motor current by intermittently flowing the motor current increases the ratio of the power consumption of the motor to the power consumption of the switching element, thereby increasing the heating effect of the motor. Thus, even if it is placed in a low temperature environment like a heat pump air conditioner, the heating time of the motor control apparatus which requires heating at the time of a compressor start can be shortened efficiently.

Moreover, since this motor control device alternates heating motor coils in order, it can heat each motor coil uniformly. In this connection, as shown in Fig. 2, the motor coils to be heated are alternately sequentially. In the section of T3, the switching element is turned on and the motor current flows. During this period of T3, each switching element is alternately turned on and off. As a result, the heating amount of each motor coil can be made uniform, the heating time can be shortened, and the flow of current in a specific phase can be avoided, which is effective for preventing the deterioration of the motor coil.

Such a conventional "motor controller" is to set the mode of controlling the motor current intermittently, performing efficient preheating control, and turning on and off the motor current at low frequency in order to intermittently control the motor current.

However, the existing motor controller has the following problems.

If all the motor currents are off (the section of T3 to T4 in Fig. 1), the stop torque is lost, so the rotor of the motor cannot be fixed at the fixed position. If the motor current flows again, the drive torque is generated in the motor. Vibrate.

In addition, this "motor control apparatus" controls the motor coils to be heated in turn to uniformly heat each motor coil. When the motor coils to be heated are alternately rotated, drive torque is also generated and the compressor vibrates.

Regarding the vibration of such a compressor, the cited documents described above may show cogging of the motor due to the occurrence of torque in the motor, but the frequency of intermittently controlling the motor current or the alternating heating of the motor coil in order It is said that it is not a problem to use it practically if the frequency of making it is small.

However, this can be a problem if the frequency is at least loud due to compressor vibration. For example, increasing the peak value of the motor current for efficient preheating control increases the drive torque in proportion to it, thereby increasing the compressor noise due to cogging.

In addition, if the frequency of controlling the motor current intermittently or the frequency of alternating the heating of the motor coil in order is lowered, a problem may occur that the control of the motor current becomes difficult. For example, a power module incorporating an inverter driving switching element may include a bootstrap circuit for supplying control power for controlling an upstream switching element (usually composed of three switching elements and corresponding to a downstream switching element). The method of charging using mainly applies. Using this method, the control power source of the switching element of the inverter can be configured as a single power source, thereby reducing the cost. As described above, the bootstrap circuit is limited in that the terminal voltage of the motor to which the upstream switch element is connected is equal to the ground voltage of the control power supply described above to charge the normal voltage. Due to this restriction, when the conduction of the downstream switching element or the reflux diodes connected in parallel to the downstream switching element does not occur for a long time, the control power of the upstream switching element is lowered and the operation of the switching element becomes unstable. Uncontrollable current can occur. Even in this case, there is a problem that the compressor noise occurs.

The present invention was conceived in view of the conventional technology as described above, and an object of the present invention is to prevent the deterioration of the motor coil and the high efficiency heating control while preheating the compressor, and at the same time reduce the noise of the compressor. The present invention provides a compressor preheating device and a method thereof.

In order to achieve the above object, the present invention provides a compressor preheating apparatus for preheating a compressor incorporating a three-phase motor, comprising: upstream switching elements and downstream switching elements for supplying a motor current to the three-phase motor. An inverter circuit; And a control signal for high frequency switching of the upstream switching element to preheat the compressor, and a control signal for low frequency switching of the downstream switching element, wherein the phase in which the motor current flows is preset. And a control circuit for changing every section.

The control circuit includes a driver for outputting a gate signal to drive the switching element, and a power supply circuit for supplying control power to the driver.

The driver performs PWM control for high frequency switching of the upstream switching element.

The driver divides the unit section into at least two sections, and sets a different PWM duty applied to the divided sections.

When the unit section is divided into a first half section and a second half section, the driver sets the PWM duty applied to the first half section to be smaller than the PWM duty applied to the second half section.

When a reflux diode is connected in parallel to the downstream switching elements, a reflux current flows through the reflux diode when the high frequency switching is performed at the upstream switching element.

The power supply circuit performs a charging operation when the voltage at the connection point between the upstream switching element and the downstream switching element is approximately equal to the ground level by the reflux current.

The present invention for achieving the above object, in the preheating method of the compressor for preheating the compressor by supplying a motor current to the three-phase motor using an inverter circuit having a plurality of switching elements, upstream switching of the inverter circuit Outputting a control signal to the device for high frequency switching and at the same time outputting a control signal to the downstream switching device of the inverter circuit for low frequency switching; And changing the phase in which the motor current flows in a predetermined order for each preset unit section.

PWM control for high frequency switching of the upstream switching element.

The unit section is divided into at least two sections, and the PWM duty applied to the divided sections is set differently.

When the unit section is divided into a first half section and a second half section, a PWM duty applied to the first half section is set to be smaller than a PWM duty applied to the second half section.

The peak value of the current induced in the motor in the first half section is smaller than the current peak value induced in the motor in the second half section.

The rotor of the motor is positioned in the first half section and preheated by the heating of the coil of the motor in the second half section.

Hereinafter, the embodiment according to the present invention will be described in detail.

The preheater of the inverter compressor according to the present invention, as shown in Figure 3, the inverter circuit composed of switching elements for controlling the motor current flowing in the motor coils (S1, S2, S3) of the three-phase motor 110 100 is provided.

3 shows a configuration of a control apparatus of a general motor and inverter circuit. The motor consists of three phase coils (s1, s2, s3)

The inverter circuit consists of six switching elements u +, v +, w +, u-, v-, w-. The upper switching elements (u +, v +, w +) and the lower switching elements (u-, v-, w-) are connected to each other and their connection points are connected to the three-phase coils (s1, s2, s3) of the motor, respectively. do. The reflux diodes D1, D2, D3, D4, D5, D6 are connected in parallel to the downstream switching elements u-, v-, w-.

The present invention includes a control circuit for controlling upstream switching elements u +, v +, w + with high frequency PWM. For example, the control circuit 200 shown in FIG. 4 shows a case of controlling the switching element u + among the upstream switching elements u +, v +, w +. The control circuit 200 includes a driver 201 for generating a gate signal for driving the switching element u + and a bootstrap circuit for supplying control power to the driver.

The driver 201 generates a gate signal for driving the switching element u +. The driver 201 is supplied with a control power supply Vcc. The control power source Vcc is generated by the direct current power source Vdc, the diode D7, and the capacitor C1 constituting the bootstrap circuit. When the downstream switching element u- conducts or the reflux diode D2 of the downstream switching element u- conducts, the connection point COM of the upstream switching element u + and the downstream switching element u- is conducted. The voltage at is almost equal to the ground level, so that the charging current (current 3) flows. Accordingly, the capacitor C1 is charged to the same voltage as the DC power supply Vdc. This charging voltage is supplied to the driver 201 as a control power supply Vcc.

Control power is also supplied to the other upstream switching elements V + and W + by the control circuit as described above.

Next, the timing at which the charging current current 3 of the capacitor C1 flows will be described. 5 shows the energization pattern of the switching elements of the inverter circuit. The hatched portion in this pattern shows the state that the switching element is chopped by the PWM signal, and the blank portion shows the state that the switching element is conducting. In an inverter circuit using a square wave control signal, it is common to chop both sides with respect to an upstream switching element and a downstream switching element. The period in which the DC power supply Vdc can be charged to the capacitor C1 is, for example, in which the downstream switching element u- is conducting or the reflux diode D2 of the downstream switching element u- in FIG. 4. Is the case when In the energization pattern of FIG. 5, the empty portion of U− is charged with the capacitor c1 because the switching element u- is conducting, and the downstream side switching is performed because the hatched portion of U + is chopped by the switching element u +. The reflux diode D2 of the element is conducted so that the capacitor C1 can be charged. As shown in FIG. 3, when the upstream switching element U + is chopped by the PWM signal, the motor driving current 1 flows to the motor coil, and in the off period of the PWM, the motor driving current 1 Although not flowing, the induced current (current 4) flows continuously due to the induction coefficient component of the motor, whereby the reflux current (current 2) flows so that the reflux diode (D2) conducts. When the reflux die D2 conducts, the potential of the connection point COM of the upstream switching element and the downstream switching element becomes almost the same level as the ground level, and the capacitor C1 is charged.

By the way, when it uses for the electricity supply pattern of FIG. 5, the capacitor C1 cannot be charged in some area | region (a) (b) (c).

When the compressor is normally operated, the charge non-charging sections (a), (b), and (c) are short in a few ms, so that a decrease in the charging voltage of the capacitor (c1) can be ignored. However, as in the case of preheating the compressor, In start-up operation, it is necessary to set the non-charge section (a) (b) (c) for a long time (a few seconds to several tens of seconds) to avoid the occurrence of noise. Extended periods adversely affect compressor preheating operation.

In consideration of this, in the present invention, the energization pattern of FIG. 6 is applied to stably charge the capacitor C1. The upstream switching element U + is chopped, and at this time, the reflux diode D2 of the downstream switching element is conductive so that the capacitor C1 can be charged. In the sections (b-1) and (c-1), the capacitor C1 is not charged because the upstream switching element U + does not conduct. Since the upstream switching element U + is not conducted in these periods (b-1) and (c-1), the charge consumption of the capacitor C1 is slow and appropriately set the capacitance of the capacitor to provide sufficient charge to drive the switching element. You can leave

When the compressor is preheated in the energization pattern of FIG. 6, the problem caused by the charge voltage of the capacitor C1 is lowered can be avoided.

FIG. 7 is a view showing control signals applied to the upstream switching element and the downstream switching element according to the energization pattern of FIG. 6, and FIGS. 8A to 8F are respective cases of changing the phase of the current flowing in the motor in FIG. 7. A diagram showing a path of a motor current corresponding to FIG.

The duty of the PWM for switching the upstream switching element divides the section T-3 into the first section T-1 and the second section T-2 until the flowing phase of the motor current alternates.

Set the duty of PWM applied to the first half section T-1 and the second half section T-2 differently. The duty of PWM in the first half is set relatively smaller than the duty of PWM in the second half.

In general, in order to perform efficient preheating control, when the peak of the motor current is increased, the compressor noise due to cogging increases as the driving torque increases in proportion to the peak of the motor current. However, as in the present invention, the duty of the PWM is made small in the first half section T-1, and a low current flows to the motor to position the rotor. Since less current flows through the motor, the noise generated by positioning the rotor is reduced. Thereafter, in the second half section T-2, the PWM duty is increased to increase the motor current. As described above, if the motor current is increased after the positioning of the rotor, the compressor noise due to cogging decreases.

In the case of performing current by alternating the phases of the current flowing in the motor, the rotor positioning is performed in the first half section after the phase change, and then the motor current is increased in the second half section.

FIG. 9 illustrates the waveform of the induced current 4 of FIG. 3 that varies in the first half and the second half.

In the first half section T-1, the rotor is positioned by passing a small current X1. Small current (X1) is set to the minimum value required for positioning of the rotor. In the second half section T-2, a large current X2 flows to generate heat to preheat the motor. The large current X2 is set to a current value at which the amount of heat required to preheat the motor can be obtained.

In this way, by controlling the heating of each motor coil uniformly, it is possible to improve the efficiency of preheating and to reduce the compressor noise due to cogging.

As mentioned above, this invention can implement preheating control of the compressor required at the time of starting of a heat pump air conditioner. According to the present invention, since the flow of the motor current is alternated, it is possible to prevent deterioration of the motor coil and to control heating with high efficiency. In addition, since the upstream switching element is always switched to a high frequency PWM signal, the charging operation in the bootstrap circuit can be stably performed, and after the positioning of the rotor by the low motor current is performed, the motor current is increased to preheat, thereby providing low noise. Can get angry.

Claims (13)

In the compressor preheating device for preheating the compressor containing a three-phase motor, An inverter circuit having upstream switching elements and downstream switching elements for supplying motor current to the three-phase motor; And Outputs a control signal for high frequency switching of the upstream switching element to preheat the compressor and a control signal for low frequency switching of the downstream switching element, and preset unit section for the phase in which the motor current flows Including control circuit to change every time, The control circuit performs PWM control for high frequency switching of the upstream switching element, dividing the PWM control section into at least two unit sections, and differently setting the duty of the PWM applied to the divided at least two unit sections. Preheating device of the inverter compressor, characterized in that. The preheating apparatus of claim 1, wherein the control circuit comprises a driver for outputting a gate signal to drive the switching element, and a power supply circuit for supplying control power to the driver. delete delete The method of claim 2, wherein when the at least two unit sections are divided into a first half section and a second half section, the driver sets the PWM duty applied to the first half section to be smaller than the PWM duty applied to the second half section. Preheater of the inverter compressor. The preheating apparatus of the inverter compressor according to claim 5, wherein when a reflux diode is connected in parallel to the downstream switching elements, a reflux current flows through the reflux diode when the high frequency switching is performed at the upstream switching element. 7. The inverter compressor according to claim 6, wherein the power supply circuit performs a charging operation when the voltage at the connection point between the upstream switching element and the downstream switching element is approximately equal to the ground level by the reflux current. Preheating method. In the preheating method of the compressor for preheating the compressor by supplying a motor current to the three-phase motor using an inverter circuit having a plurality of switching elements, Outputting a control signal to an upstream switching element of the inverter circuit for high frequency switching and at the same time outputting a control signal to a downstream switching element of the inverter circuit for low frequency switching; And And changing the phase in which the motor current flows in a predetermined order for each preset unit section, High frequency switching of the upstream switching element, PWM wool control for the high frequency switching of the upstream switching element, the PWM control section is divided into at least two unit intervals, and setting the duty of the PWM applied to the at least two divided unit intervals differently A method of preheating an inverter compressor. delete delete The preheating of the inverter compressor of claim 8, wherein when the at least two unit sections are divided into a first half section and a second half section, a PWM duty applied to the first half section is set to be smaller than a PWM duty applied to the second half section. Way. 12. The method of claim 11, wherein the peak value of the current induced in the motor in the first half section is smaller than the current peak value induced in the motor in the second half section. The method of claim 12, wherein the rotor of the motor is positioned in the first half section, and the preheating method of the inverter compressor of the second half section is preheated by the heating of the coil of the motor.

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