JPH01281353A - Protection circuit for air conditioner - Google Patents

Abstract

PURPOSE:To prevent the secondary failure of an air conditioner from occurring by providing two comparing means for comparing an electric current value with predetermined values on a different level and by judging whether the generation of an excess current is caused by the ordinary increase of a load or by the occurrence of abnormality such as short circuit. CONSTITUTION:A motor 5 for driving the refrigerant compressor of an air conditioner is supplied with electric power sent from a commercial power source 1 through a full-wave rectifier circuit 2 and an inviter 4, and the revolutional speed of the motor is controlled. A DC electric current supplied to the inverter 4 is detected by a current detector 6 and is compared with a first predetermined value a little higher than a value in ordinary operations by a first comparator 7 and also with a second preset value close to a critical value based on the current rating of parts by a second comparator 27 to be sent to the microcomputer 12 in a control section 10. When the detected current is within the second preset value even if it exceeds the first predetermined value, the control section 10 judges the detected current to be an excess current due to the ordinary increase of a load and stops power supply for a predetermined period of time and thereafter starts the supply of power. On the other hand, when the detected current exceeds the second preset value, the control section 10 judges that the excess current is caused by the occurrence of abnormality such as a short circuit, and stops the power supply to issue an alarm for abnormality. Thus, secondary failure can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides an inverter to increase the speed of an electric motor to 1lII.
The present invention relates to an overcurrent protection circuit installed in the electrical circuit of an air conditioner that is controlled by the air conditioner.

[Prior Art] FIG. 10 is an electrical circuit diagram of a conventional air conditioner disclosed in, for example, Japanese Patent Publication No. 60-13-1781. 10th
In the figure, ■ is an AC commercial power supply, 2 is a full-wave rectifier circuit, and 3 is a full-wave rectifier circuit.
4 is a smoothing capacitor, and 4 is an inverter. The inverter 4 converts the DC power supplied from the full-wave rectifier circuit 2 into AC power of an arbitrary frequency. 5 is an electric motor driven by the output of the inverter 4, and the electric motor 5 drives a compressor that compresses refrigerant. 6 is an inverter, 1
This is a current detector that detects the direct current flowing into the 7 is a comparator that compares the electric current value detected by the current detection 36 with a predetermined value; 8 is a timer; 9 is a counter; 10 is a control unit; It processes and judges the input of the counter 9 and outputs a signal for controlling the inverter 4.

Next, the operation of the conventional circuit shown in FIG. 10 will be explained. Electric power from a commercial power source 1 is converted into DC power by a full-wave rectifier circuit 2, and this DC power is converted by an inverter 4 into AC power at an arbitrary controlled frequency and supplied to an electric motor 5, so that the rotation speed of the electric motor 5 is adjusted. controlled.

During operation, a current detector 6 detects the direct current flowing into the inverter 4 and sends the current value to a comparator 7. The comparator 7 compares the input current value with a predetermined value, and if it is greater than the predetermined value, that is, if there is an overcurrent, the comparator 7 transmits the signal to the control unit l.
The control unit 10 outputs a fll1m signal to the inverter 4 to cut off the current and stop the operation of the electric fi5 for a predetermined period of time, for example, 3 minutes. At that time, the timer 8 counts the time from when the motor 5 starts operating until the time when the comparator 7 determines that there is an overcurrent, and if the time is less than the set value, the value of the counter 9 (initial value is zero) to 1
Add. Also, P4 whose time was less than the set value
If so, set the value of counter 9 to zero.

After the stop time (for example, 3 minutes) has elapsed, the electric motor 5
Restart driving. Thereafter, if the comparator 7 again determines that there is an overcurrent, 1 is added to the value of the counter 9 if the operating time of the electric motor 5 is less than the predetermined time, as in the previous case. In this way, when the comparator 7 determines that an overcurrent occurs within a predetermined time twice in a row, the value of the counter 9 becomes 2.
becomes.

When the value of counter 9 becomes 2, the control unit IO
], the control unit IO outputs an output to the inverter 4 to stop the operation, and also displays a message indicating that there is an abnormality.

[Problems to be Solved by the Invention] Conventional air conditioner protection circuits are configured as shown below, so that when an abnormality such as a short circuit occurs in the circuit of the motor or inverter, the abnormality can be prevented. Since the overcurrent must be detected at least twice before it is detected and judged, there is a problem that secondary damage may occur due to the 1 m current passing.

This invention was made to solve the above problem, and by detecting all overcurrents, it is determined whether the overcurrent is caused by normal load fluctuations or an abnormality such as a short circuit. , take the corresponding processing for each,
It is an object of the present invention to obtain a protection circuit that can prevent the occurrence of secondary destruction.

[Means for Solving the Problems] A maintenance circuit of an air conditioner according to the present invention includes a current detector that detects the current of a DC power supply, and a current value detected by the current detector that is converted to a normal overload current value. a first comparison means for comparing the current value detected by the current detector frN with a second predetermined value set to a predetermined value higher than the first predetermined value; The present invention is provided with two comparison means, and a control section that outputs a control signal based on the output signals from the first comparison means and the second comparison means to the inverter.

[For 1 year] The air conditioner protection circuit of the present invention is designed to reduce the current value because when the increase in the current value is due to load fluctuations, the current waveform becomes triangular rather than a rectangular wave due to the motor actance component. FM1 wheat that exceeds the lower comparison level (first predetermined value) cannot exceed the higher comparison level (second predetermined value).

On the other hand, in the case of an abnormal situation such as a short circuit, 1
Since there is almost no circuit resistance component, the current waveform becomes close to a rectangular wave, and the current value instantly rises to exceed both comparison levels. Taking advantage of this difference, the control unit compares the detected current value with two sets of comparison means with different comparison levels, and if the current value exceeds both the first predetermined value and the second predetermined value, Even if the control tn signal that instructs the inverter to stop energization and perform W-always-on processing, or exceeds both the first predetermined value &fY& and the second predetermined value, the human input signal is input with almost no time difference. If the two human power signals are input with a time difference, a control signal is output to the inverter that instructs the inverter to stop energization for a predetermined time and then re-energize. Therefore, the state of the device is determined by detecting and comparing the current of l[-1, and the state tr! 9 is processed accordingly.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
9 to 9 show one embodiment of the present invention, FIG. 1 is a flowchart showing the operation of the control section according to the first embodiment, and FIG. 2 is an electric circuit diagram.

In the figure, 1 is a commercial power supply and 2 is a full-wave rectifier circuit.

3 is a smoothing capacitor, 4 is an inverter, 5 is an electric motor, 6
is a current detector, 7 is a first comparator, 27 is a second comparator, 1
0 is a control unit, and 12 is a microcomputer.

In the second UA, the full-wave ¥1 current path 2 rectifies the alternating current of the commercial power supply 1 and converts it into direct current. Using this W current as a power source, the inverter 4 converts it into alternating current at an arbitrary commanded frequency and supplies it to the electric motor 5, thereby controlling the speed of the electric motor 5. The electric motor 5 is an electric motor that serves as a drive source that drives a compressor that compresses refrigerant in an air conditioner to form a cooling cycle or a heat pump cycle. Current detector 6 detects the magnitude of the DC current supplied to inverter 4. The first comparator 7 inputs the detected value of the current detection 2S6, compares it with a first predetermined value, and sends the result to the microcomputer 12.6 The first predetermined value is a value slightly higher than the normal operating state of the motor 5. Although this first predetermined value may be exceeded even in a normal state due to load fluctuations, it is not desirable to operate for 1 m for a long time in a state in which the first predetermined value is exceeded. The second comparator 27 similarly inputs the detected value of the current detector 6, compares it with a second predetermined value, and determines the value of the detected value from the microcomputer 12.
The second predetermined value, which is sent to
set to the value. The control unit 10 has a built-in microcomputer 12, and outputs a command signal to the inverter 1 to turn on/off the electricity.

Next, the operation of this protection circuit will be explained.

When the power of the air Af0 machine is turned on, the circuit shown in FIG.
2 will also start. The first comparator 7 receives the current value detected by the current detector 36 at the step 101 in FIG. 1 and compares it with a first predetermined value. If the detected value is below the first predetermined value, an H signal is sent.If the detected value exceeds the first predetermined value, an L signal is sent to the microcomputer 12. The microcomputer 12 reads this and executes vII (step 102), H
If "C" is found, the process returns to the beginning and repeats the above operations as normal processing (step 103).

If it is not H in step 1 step 102 (■-)
enters the interrupt handling routine and reads the output of the second comparison 327 in step 201. The second comparison 327 compares the detected value of the current detector 6 with a second predetermined value, and the detected value is the second predetermined value.
If it is below a predetermined value, a signal of 1 is sent to the microcomputer 12, and if it exceeds a predetermined value, a signal of - is sent to the microcomputer 12. In response to this, the microcomputer 12 makes a decision in step 202>
, I, that is, if the detected value exceeds the second predetermined value, a command signal is output to the inverter 4 to stop the road tram, and the W? Processing for responding to an abnormality such as turning on the p-report LED is performed (step 203).

Then, when the abnormality response processing (step 203) is completed (step 20-41, the process moves to step 205).Furthermore, if the signal 11, that is, the detected value, is equal to or less than the second predetermined value in step 202, Jump to the tape 205,
The control unit 10 outputs an output to the inverter 4 to temporarily stop the energization, and restarts the energization after a predetermined period of time, such as 3 minutes, has elapsed. After that, return to the beginning and repeat the above process.

The reason why the air conditioner operates and the current increases is the normal f
￥ There are cases where the load becomes large and abnormalities such as short VR occur. ￥ When the normal load becomes large and the current increases, the current flows through the motor 5 with a large actance component, so the third country As shown in FIG. ), the second predetermined value is not exceeded immediately after that, and YES is determined in step 202 of FIG.
Therefore, the process is to temporarily stop energization.

That is, the engine stops at - time and resumes operation when the load decreases.

On the other hand, if an abnormality such as a short circuit occurs, the current does not need to flow through a portion of the electric motor 115 with a large reactance, so the current changes rapidly as shown in FIG. Therefore, as shown in the figure, the detected value exceeds the first predetermined value and simultaneously exceeds the second predetermined value. That is,
At the same time as the result of step 102 in FIG. 1 is NO, the result of step 202 is NO, it is determined that n-normal occurrence has occurred, the power supply is stopped, and processing for responding to an abnormality is performed.

FIG. 5 is a flowchart showing the operation of the control section according to the second embodiment of the present invention. When the air conditioner is powered on, the microcomputer 12 of the control unit 10 also starts operating. The first comparator 7 manually compares the current value detected by the current detector 6 with a first predetermined value. If the detected value is less than or equal to the first predetermined value, an 11 signal is sent to the microcomputer 12, and if it exceeds the first predetermined value, an L signal is sent to the microcomputer 12. The microcomputer 12 reads this amount (Step 1 101),
Determine whether it is an H signal or not (step 102)J (if it is a signal, output a control signal for normal processing to the inverter 11 (step 103)), return to the beginning, and repeat the steps below.

If the step 102 determines that the signal is not 14, the process moves to the interrupt processing routine and starts the down counter (
Step 200) and the output of the second comparator 27 are read (Step 201). Set the down counter...
The value to be counted is the value that has already finished counting when the second comparator outputs the 17 signal in the case of an overcurrent due to normal load fluctuations.

The second ratio read in Ste Tsubu 201? The appearance of 2327 is judged in step 202, and if it is l(, that is, it is less than the second predetermined value, the process proceeds to step 11301 and below, the comparison of the current values is repeated, and the second comparator When both the first comparator and the first comparator begin to output H signals, the process returns to normal processing (step 103).

If the 1-signal is detected in step 202, that is, exceeds the second predetermined value, the counter is read (step 401
), if the count is over, the control unit 10 in step 501 determines that the load is due to a normal overload and that the load has decreased after a predetermined period of time (for example, 3 minutes) has elapsed. A control signal is sent to the inverter 4 to restart energization when the time is right.

If the signal is received in step 202 and the counter is counting in step 1102, it is determined that there is a malfunction such as a short circuit, and the control unit 1O stops the power supply and issues an abnormality alarm that requests the controller to perform abnormality response processing. Processing such as lighting up L[El] is performed (step 601). After that, 9! repairs the broken parts! ! Energization will not be resumed unless the process is completed.

6 to 9 are diagrams F1a showing various cases of the flowchart in FIG. 5. The 6th U'A is in a normal state. Is the current value less than or equal to the first predetermined value and the first ratio? 2 devices, 2nd ratio? Both devices are 1 (signal, and the control signal is normally processed. Figure 7 shows a low overload condition. The current value is 1.
The predetermined value was exceeded and the first comparator outputs a signal, but the second comparator outputs an I (signal), so control No. 13 continues normal processing.

FIG. 8 shows a severe overload condition. Due to the actance of the motor, the current cannot increase rapidly, so the current exceeds the first predetermined value and then exceeds the second predetermined value, but counting starts when the first predetermined value is exceeded. Since the down counter has already finished counting when the current value exceeds the second predetermined value, the process proceeds from step 402 to step 501 in FIG. 5, where the control unit 10 stops energizing.
Processing is performed to restart energization after a predetermined period of time has elapsed.

FIG. 9 shows the case of a short circuit, etc. In this case, the current does not need to flow through a part of the motor 5 where the actance is large, so the current changes rapidly, and immediately after exceeding the first predetermined value, the second predetermined value also exceeds, and the down counter is still counting. Therefore, the 5th UfA's Ste-Tub 402 to 601
Then, the control gI section 10 stops energizing and outputs a distress signal for abnormality response processing.

In addition, in the above description, it goes without saying that the outputs 11 and L of the comparisons 87 and 27 may be set oppositely. Further, in the second embodiment, the time interval from the time when the current value exceeds the first predetermined value to the time when the current value exceeds the second predetermined value is determined by using the microcomputer 12 by software. Needless to say, this may be performed by external hardware.

[Effects of the Invention] As described above, according to the present invention, the 21IJi1 comparison means for comparing current values at 76 levels is provided, and the cause of overcurrent occurrence can be determined by detecting one overcurrent occurrence. The system determines whether this is due to a normal load increase or the occurrence of a short-term abnormality, and the corresponding processing is immediately performed, thereby preventing the occurrence of secondary damage in the case of conventional abnormalities. There are effects that can be used.

[Brief explanation of the drawing]

1 to 9 show an embodiment of the present invention, FIG. 1 is a flowchart of the operation of the control section according to the first embodiment, FIG. 2 is an electric circuit diagram, and FIG. 3 is an overload case. state diagram,
FIG. 4 is a state diagram in the case of a short circuit (abnormality), 5UA is a flowchart of the operation of the control unit according to the second embodiment, and 6.
The figure is a state diagram of the normal state according to the second embodiment, FIG. 7 is a state diagram of the low overload condition according to the second embodiment, and FIG. 8 is the state diagram of the severe overload state according to the second embodiment! Figure 1, No. 9 ['
;? 1 is a state diagram of a short circuit state according to the second embodiment. FIG. 10 is an electrical circuit diagram according to a conventional example. In the figure, 2 is a rectifier circuit and 4 is an inverter. 5 is an electric motor, 6 is a current detector, 7 is a first comparator, 27 is a second comparator, 10 is a control unit, and 12 is a microcomputer. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) In a protection circuit for an air conditioner that rectifies a commercial power source to convert it into a DC power source, and detects and takes measures against overcurrent in an electric circuit configured to drive a motor from the DC power source via an inverter. , a current detector that detects the current of the DC power supply; a first comparing means that compares the current value detected by the current detector with a first predetermined value set as a normal overload current value; a second comparison means for comparing the current value detected by the device with a second predetermined value set to a predetermined value higher than the first predetermined value; and signals from the first comparison means and the second comparison means are inputted. , a control section that outputs a control signal to the inverter, and the control section outputs a control signal to the first inverter.
When a signal indicating that the current value exceeds the first and second predetermined values is outputted from the comparison means and the second comparison means, a control signal is outputted to instruct energization stop and abnormality response processing. A protection circuit for an air conditioner characterized by: (2) In a protection circuit for an air conditioner that rectifies a commercial power source to convert it into a DC power source, and detects and takes measures against overcurrent in an electric circuit configured to drive a motor from the DC power source via an inverter. , a current detector that detects the current of the DC power supply; a first comparing means that compares the current value detected by the current detector with a first predetermined value set as a normal overload current value; a second comparison means for comparing the current value detected by the device with a second predetermined value set to a predetermined value higher than the first predetermined value; and signals from the first comparison means and the second comparison means are inputted. , a control section that outputs a control signal to the inverter, and the control section outputs a control signal to the first inverter.
A signal indicating that the current value exceeds the first predetermined value is input from the comparing means, and a signal indicating that the current value exceeds the second predetermined value is input from the second comparing means, and both signals are inputted. When input with a time difference, it outputs a control signal that stops energization for a predetermined period of time, and when both signals are input almost simultaneously, it outputs a control signal that instructs to stop energization and handle abnormalities. protection circuit for air conditioners.