JPH0518588A - Protecting method for overcurrent of air conditioner - Google Patents

Abstract

(57) [Abstract] [Purpose] In addition to providing fast protection in the event of overcurrent, it also provides the maximum capacity within the allowable current range. [Composition] When the current detected by the current detector 10 reaches the first current value S1 or more, the operation of the compressor is stopped (step S8), and the first current value S1>current> second current value In the case of, the frequency of the AC power output from the inverter device is reduced by a predetermined value (step S9), and in the case of the second current value>current> the third current value, correction is performed in a decreasing direction with respect to the increase amount of the target frequency. (Steps S10 and S11), when the third current value> current, normal operation is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent protection method for an air conditioner which controls the operating current of the air conditioner within an appropriate range.

[0002]

2. Description of the Related Art As a conventional technique of such an overcurrent protection method, there is one disclosed in Japanese Patent Publication No. 2-620. What is described in this publication is a zone for stopping the operation of the compressor with respect to the current value detected by the current detector, a zone for decreasing the frequency, a zone for not changing the frequency, and an alternating current output from the inverter device. A zone is provided in which the frequency of the electric power is increased by a predetermined value and the frequency is adjusted according to the frequency command signal.

[0003] In such a conventional technique, the maximum operating capacity of the current value supplied from the commercial power source can be obtained without exceeding the maximum permissible range of the current value.

[0004]

With this conventional technique, for example, if the maximum allowable value of current is 15 A,
Generally, the current is controlled in the range of 14 A to 15 A, but the zone for lowering the frequency is set to 15 A or higher, so the operating current exceeds 15 A for a short time (within the current breaker allowable range). There was a problem. Further, when the compressor is locked and an excessive overcurrent flows, there is a problem that the speed of lowering the frequency cannot catch up and the compressor is burned. Therefore, there is a problem that the fluctuation range of the operating current is in the range of 15 + α to 14 A, which exceeds the allowable current range, and the fluctuation range of the current, that is, the capacity is wide and the temperature fluctuation range is also wide. ..

In order to solve such a problem, the present invention provides quick protection even when the compressor is locked and an excessive current suddenly flows, and the current can be suppressed within the allowable current range. It provides a protection method.

[0006]

According to the overcurrent protection method of the present invention, a signal output means for outputting a frequency command signal based on a room temperature and a set temperature and an electric power supplied from a commercial power source according to the frequency command signal. An air conditioner that supplies the output of the inverter device to the compressor, and a current detector that detects the current of the power supplied from the commercial power supply is provided. , The first current value, the second current value, and the third current value are set to decrease in order with respect to the current detected by the current detector, and when the current is larger than the first current value, When the operation of the compressor is stopped and the current is smaller than the first current value and larger than the second current value, the frequency of the AC power output from the inverter device is reduced by a predetermined value, and the current is smaller than the second current value. Third When the frequency command signal changes in the increasing direction of the frequency when the current value is larger than the current value, the amount of increase in the frequency of the AC power output from the inverter device is made smaller than the amount of increase in the frequency command signal, and the current is the third current value. When it is smaller, the frequency of the AC power output from the inverter device is set to the frequency corresponding to the frequency command signal.

[0007]

When the overcurrent protection method configured as described above is used, the current is compared with the first to third current values (first current value> second current value> third current value). Then, when the current> the first current value, the operation of the compressor is stopped, when the first current value> the current> the second current value, the frequency is lowered, and the second current value> the current> the third. In the case of current, the width of increase in frequency is reduced only when the frequency increase signal is output, and in the case of the third current value> current, normal operation is performed.

[0008]

EXAMPLES Examples in which the present invention is applied to a split type air conditioner will be described below. FIG. 2 is a main part electric circuit diagram of the outdoor unit.

In this figure, an alternating current (100 V) supplied from a commercial power source 1 is input to a full wave rectifier 5 via a varistor 2, a noise filter 3 and a reactor 4. The DC output of the full-wave rectifier 5 is boosted to 280V DC by the voltage doubler rectifier 7 including three capacitors. This DC 280V is input to the three-phase bridge type inverter 6.

The inverter 6 switches a DC 280V based on the PWM theory to generate a pseudo sine wave having an effective value of 100V, and a compressor 8 using a three-phase induction motor.
Supply to. The capacity of the compressor 8 depends on the output frequency of the pseudo sine wave.

The current detection circuit 9 includes a current transformer 10
After rectifying and smoothing the detected alternating current to convert it to a direct current voltage, A / D (anagro / digital) of the microprocessor 11
Output to the conversion input terminal. Therefore, the DC voltage output from the current detection circuit 9 also increases / decreases as the AC current supplied from the commercial power source 1 increases / decreases. Microprocessor 11
After changing the DC voltage to a digital value, the digital value A and the first to third current values S1 to S3 (first current value> second current value> third current value) are larger or smaller. And perform the following control.

(1) A> S ₁ abnormality processing (operation stop of the compressor 8 etc.) (2) S ₁ ≧ A> S ₂ inverter output frequency decrease (3) S ₂ ≧ A> S ₃ inverter output frequency increase (4) S ₃ ≧ A Normal operation The compressor temperature sensor 12 detects the temperature of the compressor 8 using the temperature detection circuit, converts it to a DC voltage, and then outputs it to the A / D conversion input terminal of the microcomputer 11. To do. Microcomputer 1
1 is based on the magnitude relationship between the compressor temperature T and the first, second, and third set compressor temperatures S ₄ , S ₅ , S ₆ (S ₄ > S ₅ > S ₆ ), for example, The following control operation is performed.

(1) T> S ₄ abnormality processing (operation stop of compressor 8 etc.) (2) S ₄ ≧ T> S ₅ inverter output frequency decrease (3) S ₅ ≧ T> S ₆ inverter output frequency increase Prohibition (4) S ₆ ≧ T Normal operation The serial signal circuit 13 receives control data from an indoor unit (not shown) and sends it to the microcomputer 11. When performing normal operation, the microcomputer 11 starts / stops the compressor 8 and controls the inverter output frequency according to the control data from the indoor unit. The operation control of the compressor 8 is performed by power-amplifying the signal from the microcomputer 11 by the switching signal amplifier 14 and supplying the amplified signal to each transistor of the inverter 6.

That is, the microcomputer 11 outputs the ON / OFF signal of the transistor forming the inverter circuit 6 based on the PWM theory in accordance with the frequency signal sent from the indoor unit. The relay contact piece 15 and the phototriac 16 operate under the control of the microcomputer 11. When the relay contact piece 15 is turned on, the outdoor fan 17 is operated, and when the phototriac 16 is turned on, the four-way switching valve 18 is switched.

FIG. 1 shows the microprocessor 1 shown in FIG.
3 is a flowchart showing main operations during current protection of No. 1; In this flowchart, at the start of operation, initialization is performed in step S1. Then step S
In step 2, it is determined whether or not the frequency command signal is input from the indoor unit. When the frequency command signal is input, the process proceeds to step S3, and the target frequency F is set to the frequency of the frequency command signal. When the frequency command signal is not input, the previously set target frequency F is used as it is.

In step S4, the current value A detected by the current transformer 10 is input, and the following steps S5 to S7 are performed.
The range of the current value A is determined by.
If "A>S1", that is, current value> first current value is determined in step S5, the process proceeds to step S8 and abnormality processing is performed. It should be noted that this S1 is a value set as an allowable maximum current value.

In step S6, "S1>A>S2", that is, the first current value>A> the second current value is determined, and the current A
Is within this range, the process proceeds to step S9 and the target frequency F
To F-α. The value of α varies depending on the variable range of frequency and the step size, but in the present invention, as an example, 10H
Set to z.

In step S7, "S2>A>S3", that is, the second current value>A> third current value is judged. When the current A is within this range, first, in step S10, the current output frequency f It is determined whether the target frequency F is larger. That is, it is determined whether or not a frequency command signal for increasing the target frequency is input. When the target frequency F does not change (F = f) or when the target frequency F decreases (F
In <f), the current A does not change or tends to decrease. Therefore, even if “S2>A> S3”, the protection operation for reducing the current value is not necessary. During this time, the operation corresponding to the load is continued.

When the target frequency F is increasing in step S10 (F> f), the process proceeds to step S11. In step S11, the increase amount of the target frequency F is changed to 1/2. For example, when the target frequency F is 130 Hz with respect to the current output frequency 110 Hz, the target frequency F is 120
It is corrected to Hz. This correction is not limited to 1/2. For example, even if the optimum value is set based on the amount of change in the capacity of the compressor when the frequency is changed by 10 Hz and the amount of increase or decrease in the current value when the frequency is changed by 10 Hz. Good. Further, a predetermined frequency decrease amount may be set so that the increase amount of the target frequency does not become zero.

In step S12, the current output frequency f is increased / decreased by 1 Hz so that f = F is satisfied until f = F is determined in step S13. During this period, step S
14. In step S15, it is determined that the current value A is A> S1 (the same operation as in steps S4 and S5), and A> S1.
If YES is determined, the process proceeds to step S8, and abnormality processing is performed.

When F = f is determined in step S13, the process proceeds to step S16. That is, the operation from step S2 is performed again.

FIG. 3 is a diagram showing a change in current when the flow chart shown in FIG. 1 is used. As an example, the first current value S1 is set to 15.0 [A], the second current value S2 is set to 14.8 [A], and the third current value is set to 14.5 [A]. .. First, the operation of the air conditioner is started at time t0. After the current is stabilized at time t1, the air-conditioning load and frequency are balanced, and then the load is increased (increase in the number of employees in the harmony room, opening and closing of doors and windows, etc.), and time t2.
If the current stabilizes at, it stabilizes at this current value unless the target frequency is increased. If there is no increase in frequency or increase in current due to overload, the current stabilizes as shown by the dotted line even after the time t3, and when a frequency command signal to reduce the frequency is given, the current as shown by the dotted line passes after the time t3. Will decrease.

At time t3, when the frequency command signal for substantially increasing the frequency is given, step S1 shown in FIG.
1 is executed so that the frequency rises, that is, the current rise rate slows down. Actually, the correction in step S11 causes the current frequency to gradually increase and the amount of increase in frequency to gradually decrease. Therefore, although the frequency increases and the current increases, the time at which the current reaches the second current value S2 can be delayed until time t4. The alternate long and short dash line represents the change in the current when the correction in step S11 was not performed, and the time for the current to reach the second current value S2 is earlier at time t3.5.

When the current exceeds the second current value S2 at time t4, step S6 is determined and step S9 is executed to lower the target frequency by a predetermined value (10 Hz). This operation is repeated every predetermined period (every cycle of the flowchart) until the current becomes smaller than the second current value S2 at times t5, t6, and t7, the frequency decreases, and the current also decreases. If F> f at time t8, the frequency rises again, and the current also increases. Therefore, at time t9,
At t10 and t11, step S9 is performed again to decrease the frequency. In this way, the current can be stabilized near the second current value S2. After this, when a new frequency command signal is input by regular communication or sudden communication from the indoor unit and the target frequency F is rewritten, time t
The operation from 3 is repeated again to change the current value to the second current value S.
It stabilizes around 2. When the target frequency drops, if the current is equal to or less than the second current value S2, the current is stable.

After that, when an abnormality such as a lock of the compressor occurs and the current suddenly increases, an abnormality process, for example, a process of stopping the operation of the compressor is performed in step S8.

By thus performing the current protection in accordance with the flow chart shown in FIG. 1, it is possible to prevent a rapid increase in the current, prevent an abnormal processing operation due to an overshoot of the current, and prevent the second current from flowing even during overload. It can be stabilized near the current value of.

[0027]

According to the overcurrent protection method of the present invention, the current is the first
When the current value is reached, the operation of the compressor is stopped, so that the current does not exceed the first current value. When the current exceeds the second current value, the frequency is lowered to prevent the current from increasing.
When the current exceeds the third current value, the normal operation is performed while the target frequency is not increased, and when the target frequency is increased, the amount of increase in the target frequency is reduced. It is possible to prevent the current overshoot by slowing the increase rate of the output frequency, that is, the increase rate of the current. That is, it is possible to prevent the current overshoot from exceeding the first current value even when the second current value is brought close to the first current value.

Further, even when the current is between the second current value and the third current value, the current can be increased until it approaches the second current value, and the operating current range of the compressor is increased. It can be expanded to almost the second current value.

Therefore, the actual maximum operating current can be made much closer to the first current value than the conventional one with respect to the allowable current range (first current value), and the maximum operation obtained within the allowable current range. The ability is increased.

[Brief description of drawings]

FIG. 1 is a flowchart showing main processing of a microprocessor of an outdoor unit for performing a protection operation according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a control device for an outdoor unit of a split type air conditioner to which an embodiment of the present invention is applied.

FIG. 3 is a diagram showing an example of current change when the protection operation of FIG. 1 is performed.

[Explanation of symbols]

 1 Commercial power supply 6 Inverter 8 Compressor 9 Current detection circuit 10 Current transformer 11 Microprocessor

Claims (1)

Claim: What is claimed is: 1. A signal output means for outputting a frequency command signal based on a room temperature and a set temperature, and an electric power supplied from a commercial power source is changed to an AC power having a frequency corresponding to the frequency command signal. In an air conditioner that supplies the output of this inverter device to the compressor, a current detector that detects the current of the power supplied from the commercial power source is provided. The first current value, the second current value, and the third current value are set to decrease in sequence with respect to the detected current, and when the current is larger than the first current value, the operation of the compressor is stopped. However, when the current is smaller than the first current value and larger than the second current value, the frequency of the AC power output from the inverter device is reduced by a predetermined value, and the current is smaller than the second current value and smaller than the third current value. When big When the frequency command signal changes in the increasing direction of the frequency, the increase amount of the frequency of the AC power output from the inverter device is made smaller than the increase amount of the frequency command signal, and when the current is smaller than the third current value, the inverter is An overcurrent protection method for an air conditioner, characterized in that the frequency of the AC power output from the device is set to a frequency according to the frequency command signal.