JPH05322324A - Inverter air conditioner - Google Patents

Abstract

PURPOSE:To perform a positive protection of discharging operation without changing an operating frequency range by a method wherein there are provided means for estimating a winding temperature of a compressor and protecting against an increased temperature and means for changing-over an increased temperature protecting temperature and at the same time the protection temperature is decreased in the case that an operating frequency of the compressor is at its ultra-low speed. CONSTITUTION:An inverter air conditioner is comprised of a converter 4 for converting AC into DC and a converter 6 for converting DC into AC and driving a compressor 7. As the compressor 7 is driven, refrigerant is cooled by an outdoor heat exchanger 8 and indoor air is cooled by an indoor heat exchanger 10. In this case, at an outdoor control part 20, the operating frequency is determined by an operating frequency limiting means 25, and the operating frequency is outputted to a wave-form outputting circuit 21 through a discharging protection means 22. The discharging protection means 22 cuts a signal for the wave-form outputting circuit 21 and stops operation if the discharging temperature detected by a discharging temperature sensor 11 and a discharging temperature sensing means 23 is higher than a protection temperature set by the protection temperature changing-over means 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a motor control device for an inverter air conditioner, and more particularly to improvement of its reliability.

[0002]

2. Description of the Related Art In inverter air conditioners, the operating range has been recently expanded to the low frequency side. On the other hand,
As shown in Japanese Patent Laid-Open No. 61-89437, as a winding temperature rise protection of a compressor, the temperature of a refrigerant gas discharged from the compressor is detected, and the winding temperature is estimated based on the detected temperature. It is known to provide winding temperature rise protection. However, in the operation in the ultra-low frequency range, the flow rate of the refrigerant flowing through the refrigerant pipe decreases, the temperature gradient between the winding temperature and the discharge temperature increases, and the protection may not work sufficiently.

The configuration of the conventional example will be described with reference to FIG. A conventional inverter air conditioner has a converter (AC / DC converter) 4 for converting a commercial power supply to DC, and an inverter (DC / AC converter) for converting a DC power supply to an AC power supply as main circuits.
6. As a refrigeration cycle, a compressor 7 that pressurizes and circulates a refrigerant composed of an electric motor and a compression element, an outdoor heat exchanger 8 that exchanges heat between the refrigerant and outdoor air, an expansion valve 9 that adjusts the amount of squeezing of the refrigerant, and a refrigerant. Indoor heat exchanger 1 for heat exchange of indoor air
0, a waveform output circuit 21 that outputs a waveform signal of an inverter as an outdoor control unit, a discharge temperature sensor 11 that detects the temperature of the discharged refrigerant, and a discharge temperature detection unit 2 that detects the discharge temperature.
3, discharge protection means 22 for stopping the operation at a fixed protection temperature, and operation frequency limiting means 25 for limiting the operation frequency according to information such as the operation current.

Next, the operation will be described. In FIG. 6, a compressor 7 is a DC power source, which is a commercial power source once converted into a DC power by a converter (AC / DC converter) 4, based on a waveform signal from a waveform output circuit 24. ) 6, it is driven by an AC power source converted into a three-phase AC having a desired frequency and voltage. When the compressor 7 operates, the refrigerant is compressed into high temperature and high pressure and flows through the pipe to the outdoor heat exchanger 8, where heat is exchanged with outdoor air, and the refrigerant is cooled. Next, the cooled refrigerant is throttled by the expansion valve 9 and flows into the indoor heat exchanger 10 to exchange heat with the indoor air and cool the indoor air. The outdoor control unit 20 requests the operation such as the temperature difference between the indoor air temperature and the set temperature (operation required frequency).
On the other hand, the operating frequency is determined by the operating frequency limiting unit 25 that receives the constraint conditions (not shown) such as the operating current and the temperature of the electric component, and the operating frequency is sent to the waveform output circuit 21 via the discharge protection unit 22. Output. The discharge protection means 22 is
The preset protection temperature is compared with the discharge temperature detected by the discharge temperature sensor 11 and the discharge temperature detection means 23, and if the discharge temperature is equal to or higher than the protection temperature, the signal to the waveform output circuit is cut (operation is stopped). .. FIG. 7 shows an operation flowchart when the above protection operation is performed by the microcomputer. After the start, the discharge temperature is fetched (step 105), it is judged whether or not it is the protection temperature or more (step 106), and if it is the protection temperature or more, the discharge temperature protection is stopped (step 107).

[0005]

The conventional inverter air conditioner is constructed as described above, and the winding temperature of the compressor is protected. However, when it is attempted to operate at a low frequency, the refrigerant circulation amount decreases and the temperature difference between the compressor winding temperature and the discharge temperature becomes large, and there arises a problem that the discharge temperature protection cannot sufficiently protect the winding temperature rise. .. The above will be described in more detail with reference to FIG. 3 “Relationship between temperature difference ΔT between winding temperature and discharge temperature and operating frequency”. From FIG. 3, it can be seen that ΔT is small (ΔT2) when the operating frequency is high (F2), and ΔT is large (ΔT1) when the operating frequency is low (F1). In order to protect the winding temperature with the discharge temperature, the value obtained by adding ΔT to the allowable temperature of the winding must be the protection temperature of the discharge temperature. If the conventional lowest frequency is F2, Δ
T2 + winding allowable temperature is acceptable, but if the protection frequency is the same and the lowest frequency is F1, ΔT1-ΔT will be
I'm running out of two.

The present invention has been made in order to solve the above problems, and sufficiently protects the winding temperature of the compressor even if the compressor is operated at a low frequency, or raises the temperature. When is large, the objective is to obtain an inverter air conditioner that limits the lower limit of the operating frequency and protects the winding temperature rise.

[0007]

An inverter air conditioner according to claim 1 has a converter for converting an alternating current into a direct current and an inverter for converting the direct current into an arbitrary alternating current and driving a compressor. In the compressor, means for detecting the temperature of the refrigerant gas discharged from the compressor to estimate the winding temperature of the compressor to protect the winding temperature rise, and winding by the operating frequency applied to the compressor. And a protection temperature switching means for switching the temperature rise protection temperature. The protection temperature switching means lowers the protection temperature when the compressor operating frequency is extremely low.

An inverter air conditioner according to a second aspect of the present invention is an inverter air conditioner having a converter that converts alternating current into direct current and an inverter that converts the direct current into arbitrary alternating current and drives a compressor. The operating temperature limiting means and the operating frequency limiting means for detecting the temperature of the refrigerant gas discharged from the compressor, the minimum frequency switching means having a temperature at which the temperature of the refrigerant gas discharged from the compressor is a certain temperature. If the above is satisfied, the lowest frequency is increased.

[0009]

In the inverter air conditioner of the first aspect, when the operating frequency is low, discharge protection is performed at a lower protection temperature.

In the inverter air conditioner of the second aspect, the minimum frequency is raised when the discharge temperature is high.

[0011]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an inverter air conditioner according to a first embodiment of the present invention. In the figure, 4 is a converter that temporarily converts an AC commercial power source composed of a rectifying diode, an electrolytic capacitor, etc. into DC, 6 is an inverter composed of switching elements such as transistors, and 7 is a refrigerant composed of an electric motor and a compression mechanism section. Compressor for pressurizing and circulating
Is an outdoor heat exchanger for exchanging heat with the refrigerant and outdoor air, 9 is an expansion valve for adjusting the amount of squeezing of the refrigerant, 10 is an indoor heat exchanger for exchanging heat between the refrigerant and indoor air, and 20 is an outdoor controller,
A waveform output circuit 21 that outputs a waveform signal of the inverter, a discharge temperature sensor 11 that detects the temperature of the discharge refrigerant, a discharge temperature detection unit 23 that detects the discharge temperature, a discharge protection unit 22 that stops the operation at a designated protection temperature, It is composed of a protection temperature switching means 24 for switching the protection temperature according to the operating frequency and an operating frequency limiting means 25 for limiting the operating frequency according to information such as operating current. Is.

Next, the operation will be described. In FIG. 1, the compressor 7 is an inverter (DC / AC converter) based on a waveform signal from the waveform output circuit 24, which is a DC power source that is a commercial power source once converted into DC by a converter (AC / DC converter) 4. It is driven by an AC power supply converted into a three-phase AC having a desired frequency and voltage by the reference numeral 6. When the compressor 7 operates, the refrigerant is compressed into high temperature and high pressure and flows through the pipe to the outdoor heat exchanger 8, where it exchanges heat with the outdoor air, the refrigerant is cooled, and the next cooled refrigerant is Expansion valve 9
Is squeezed by and flows into the indoor heat exchanger 10 to exchange heat with the indoor air and cool the indoor air. The outdoor control unit 20 receives an operating request (operating request frequency) such as a temperature difference between the indoor air temperature and a set temperature, and inputs operating conditions such as operating current and electrical component temperature (not shown). The limiting means 25 determines the operating frequency, and outputs the operating frequency to the waveform output circuit 21 via the discharge protection means 22. The discharge protection unit 22 includes a protection temperature set by the protection temperature switching unit 24 corresponding to the operating frequency, the discharge temperature sensor 11, and the discharge temperature detection unit 2.
The discharge temperature detected in 3 is compared, and if the discharge temperature is equal to or higher than the protection temperature, the signal to the waveform output circuit is cut (operation is stopped).

FIG. 2 shows a flow chart when the above is controlled using a microcomputer. When the program starts, the operating frequency is fetched (step 101), the operating frequency is judged (step 102), and the operating frequency is F2.
If below, set protection temperature to TLOW (Step 10
4) If the operating frequency is F2 or higher, set the protection temperature to HIGH.
(Step 103). Next, the discharge temperature is taken in (step 105), it is judged whether or not it is at or above the protection temperature (step 106), and if it is at or above the protection temperature, the discharge temperature protection is stopped (step 107).

Example 2. Hereinafter, another embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing an inverter air conditioner according to a second embodiment of the present invention. In the figure, 4 is a converter that temporarily converts an AC commercial power supply composed of a rectifying diode, an electrolytic capacitor, etc. into DC, 6 is an inverter composed of switching elements such as transistors,
Reference numeral 7 denotes a compressor that pressurizes and circulates a refrigerant including an electric motor and a compression mechanism portion, 8 an outdoor heat exchanger that exchanges heat between the refrigerant and outdoor air, 9 an expansion valve that adjusts the amount of squeezing of the refrigerant, and 10 a refrigerant and the indoor portion. An indoor heat exchanger that performs heat exchange of air, 20 is an outdoor control unit, a waveform output circuit 21 that outputs a waveform signal of an inverter, and a discharge temperature sensor 1 that detects the temperature of the discharged refrigerant.
1. Discharge temperature detection means 23 for detecting the discharge temperature, discharge protection means 22 for stopping the operation at a fixed protection temperature, minimum frequency switching means 26 for switching the minimum frequency according to the discharge temperature, operating frequency according to information such as operating current It is composed of the operating frequency limiting means 25 for limiting, and is the same as the conventional one except the minimum frequency switching means 26.

Next, the operation will be described. Since the basic part is the same as that of the first embodiment, only different parts will be described. The lowest frequency switching means 26 changes the lowest frequency setting value for the operating frequency limiting means 25 according to the detected discharge temperature. The discharge protection unit 22 compares the protection temperature set by the protection temperature switching unit 24 to the operating frequency and the discharge temperature detected by the discharge temperature sensor 11 and the discharge temperature detection unit 23, and the discharge temperature is equal to or higher than the protection temperature. For example, cut the signal to the waveform output circuit (stop operation).

FIG. 5 shows a flow chart when the above is controlled using a microcomputer. When the program starts, the discharge temperature is fetched (step 105), it is judged whether the temperature is the protection temperature or higher (step 106), and if it is the protection temperature or higher, the discharge temperature protection is stopped (step 107). Next, the discharge temperature is judged (step 201), and if the discharge temperature is low, the lowest frequency is set to F1 (step 20).
3) If the discharge temperature is high, the lowest frequency is set to F2 (step 202), and it is further determined whether the operating frequency is higher than the lowest frequency (step 204). If the operating frequency is lower than the lowest frequency, the operating frequency is set. Raise (step 205).

[0017]

The present invention has the following effects. The inverter air conditioner according to claim 1, wherein the inverter air conditioner includes a converter that converts alternating current into direct current, and an inverter that converts the direct current into arbitrary alternating current and drives a compressor. Means for detecting the temperature of the refrigerant gas to estimate the winding temperature of the compressor to protect the winding temperature rise, and a protection temperature switch for switching the winding temperature rise protection temperature according to the operating frequency applied to the compressor. Since the protection temperature switching means is configured to lower the protection temperature when the compressor operating frequency is extremely low, the protection temperature switching means discharges without changing the operating frequency range by switching the protection temperature at the operating frequency. Ensure protection.

An inverter air conditioner according to a second aspect of the present invention is an inverter air conditioner having a converter that converts alternating current into direct current and an inverter that converts the direct current into arbitrary alternating current and drives a compressor. The operating temperature limiting means and the operating frequency limiting means for detecting the temperature of the refrigerant gas discharged from the compressor, the minimum frequency switching means having a temperature at which the temperature of the refrigerant gas discharged from the compressor is a certain temperature. In the above case, since the lowest frequency is set to be high, by switching the lowest frequency depending on the discharge temperature, it is possible to reliably perform discharge protection without changing the protection temperature.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between a temperature difference ΔT between a winding temperature and a discharge temperature and an operating frequency.

FIG. 4 is a control block diagram showing a second embodiment of the present invention.

FIG. 5 is a flow chart showing a second embodiment of the present invention.

FIG. 6 is a control block diagram of a conventional inverter air conditioner.

FIG. 7 is an operation flowchart of a conventional inverter air conditioner.

[Explanation of symbols]

 4 converter 6 converter 7 compressor 8 outdoor heat exchanger 9 expansion valve 10 indoor heat exchanger 11 discharge temperature sensor 20 outdoor control unit 21 waveform output circuit 22 discharge protection unit 23 discharge temperature detection unit 24 protection temperature switching unit 25 operating frequency limit Means 26 Minimum frequency switching means

Claims (2)

[Claims] 1. An inverter air conditioner having a converter for converting alternating current to direct current and an inverter for converting the direct current to arbitrary alternating current and driving a compressor, the temperature of a refrigerant gas discharged from the compressor. Means for detecting the winding temperature of the compressor and estimating the winding temperature of the compressor to protect the winding temperature rise;
Protective temperature switching means for switching the winding temperature rise protective temperature according to the operating frequency applied to the compressor, and the protective temperature switching means lowers the protective temperature when the compressor operating frequency is extremely low. A characteristic inverter air conditioner. 2. A temperature of refrigerant gas discharged from the compressor in an inverter air conditioner having a converter for converting alternating current into direct current and an inverter for converting the direct current into arbitrary alternating current and driving a compressor. And a minimum frequency switching means for switching the minimum operable frequency and an operating frequency limiting means, wherein the minimum frequency switching means sets the minimum frequency if the temperature of the refrigerant gas discharged from the compressor is equal to or higher than a certain temperature. Inverter air conditioner characterized by high price.