JPH0611217A - Air conditioner - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable effective reduction of power loss without compromising the comfort of indoor air conditioning. [Constitution] The inverter frequency determining means 16 is set at room temperature Ta.
And the inverter frequency f is determined based on the input of the set value Ts. When the low frequency region discrimination means 18 determines that f belongs to the low frequency region, it sends a discrimination signal to that effect to the V / f control means 17. The V / f control means 17 only determines when the compressor 1 is locked or not.
Although the inverter output power V is temporarily increased, the inverter unit 13 is operated at the inverter output voltage V that minimizes the inverter input current I for most of the time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for detecting a compressor lock occurrence by detecting an inverter input current.

[0002]

2. Description of the Related Art When performing variable speed control of a compressor motor by V / f control of an inverter device, a so-called lock phenomenon occurs in the compressor due to insufficient rotation torque of the motor and overload of the refrigeration cycle. When such a compressor lock occurs, it is necessary to temporarily stop the operation of the compressor, but the determination of whether the compressor lock has occurred has been conventionally performed as follows.

That is, FIG. 6 is a characteristic diagram showing the relationship between the inverter output frequency f and the inverter input current I. The straight line (a) is a straight line (b) when operating at maximum load.
Is a straight line (c) when compressor lock begins to occur
Indicates the case where the operation is continued in the compressor locked state. As shown in this figure, since the current values on the respective straight lines are different, it is possible to determine whether or not the compressor lock is currently occurring by detecting the current value at a certain frequency.

In this case, in a region where the frequency is high to some extent, the difference in the current values between the straight lines (a) and (b) is large, so that it is easy to determine whether or not the lock has occurred. In the area, since the difference between the current values is small, it is difficult to determine the occurrence of lock.

Therefore, conventionally, as shown in FIG. 7, the inverter output voltage V is set to a level higher than the original level (dotted line part in FIG. 7) in the low frequency region. According to this, even in the low frequency region, as shown in FIG.
It is possible to increase the difference in current value between the straight lines (a) and (b) at, and it is possible to easily determine the occurrence of lock.

[0006]

However, as described above, constantly increasing the level of the inverter output voltage V in the low frequency region means that the compressor is driven with the motor efficiency lowered, This results in increased power loss.

Therefore, in order to reduce such power loss as much as possible, the voltage V is set to a low level and the inverter output frequency f is set to a predetermined value (for example, 10 to 20 minutes) every predetermined time (for example, 10 to 20 minutes). There is also a technique for discriminating the occurrence of compressor lock by increasing the frequency above 30 Hz) so that the difference in current between the straight lines (a) and (b) in FIG. 6 becomes large.

However, increasing the inverter output frequency in order to determine the occurrence of the compressor lock causes an essentially unnecessary increase in capacity,
There was still room for improvement in terms of reducing power loss and comfort of indoor air conditioning.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an air conditioner capable of effectively reducing power loss without impairing the comfort of indoor air conditioning.

[0010]

[Means for Solving the Problems] As means for solving the above problems, a first aspect of the present invention is an air conditioner for performing variable speed control of a compressor motor by controlling an inverter output voltage and an inverter output frequency of an inverter device. In the machine, by comparing the value of the inverter output frequency with a preset setting value, a low frequency region determining means for determining whether or not the value is within a low frequency region, and the low frequency region determining means. When it is determined that the means is in the low frequency region, the detected value of the inverter input current when the inverter output voltage is increased so that the compressor motor is overexcited and the preset value are compared. However, when this detected value is greater than or equal to this set value, a command to stop the operation of the inverter device is output. When it is less than the set value,
V / f control means for outputting a command for operating the inverter device for a predetermined time at an inverter output voltage of at least a level lower than that at the time of comparison is provided.

According to a second aspect of the present invention, in the configuration of the first aspect, the V / f control means continuously or stepwise changes the inverter output voltage when the detected value is below the set value. By increasing or decreasing, the minimum value or a value near the minimum value of the detected value of the inverter input current is obtained, and the inverter output voltage corresponding to the minimum value or a value near the minimum value is used to operate the inverter device. An air conditioner, which outputs a command for a predetermined time.

[0012]

In the configuration of the first aspect of the invention, the low frequency region discrimination means compares the value of the inverter output frequency with the set value to discriminate whether or not the value is within the low frequency region. If it is determined that the frequency is within the low frequency range, V /
The f control means increases the inverter output voltage so that the compressor motor is in the overexcited state. This allows
Even in the low frequency range, the level of the inverter input current rises, so that it is easy to determine the occurrence of lock.

Then, the V / f control means compares the detected value of the inverter input current at this time with the set value, and if the detected value is equal to or larger than the set value, it is determined that the lock is generated, Outputs an inverter stop command.

On the other hand, if the detected value is below the set value,
Since it is considered that the lock has not occurred, the operation in the low frequency region is continued as it is. However, the level of the inverter output voltage after the determination is made to be at least lower than the level at the time of determination in order to reduce the power loss.

The first aspect of the present invention merely lowers the level of the inverter output voltage after the determination of lock is made lower than the level at the time of the determination. The voltage level is controlled to be the minimum level required.

That is, when the inverter output voltage is continuously increased or decreased, the inverter input current also continuously changes, so that the minimum value of the detected value of the inverter input current can be found. However, when the inverter output voltage is increased or decreased stepwise, the change of the inverter input current also becomes stepwise, so that it is not always possible to find the minimum value, and it becomes a value near the minimum value.

The V / f control means outputs a command to operate the inverter device for a predetermined time according to the inverter output voltage corresponding to the minimum value of the inverter input current thus found or a value in the vicinity thereof. .

[0018]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, in the heating mode, the refrigerant discharged from the compressor 1 is sent to the indoor heat exchanger 3 through the four-way valve 2 and undergoes heat exchange there. The refrigerant discharged from the indoor heat exchanger 3 is sent to the outdoor heat exchanger 5 through the expansion valve 4 and is again heat-exchanged there. The refrigerant exiting the outdoor heat exchanger 5 is circulated through the four-way valve 2 to the suction port of the compressor 1. In addition, 7 is an indoor fan and 8 is an outdoor fan.

The compressor 1 includes a compressor motor 9
The compressor motor 9 is controlled by an inverter device 10 at a variable speed. The inverter device 10 includes a converter unit 11, a smoothing capacitor 12, and an inverter unit 13,
AC power is supplied to the converter unit 11 from an AC power supply 13.

The inverter control device 14 for controlling the inverter device 10 includes an inverter frequency determining means 16, V /
It has an f control means 17, a low frequency area discrimination means 18, and a timer 19. Then, the inverter frequency determination means 16 inputs the room temperature Ta from the room temperature sensor 20 attached to the indoor unit and the room set temperature Ts from the room temperature setting device 21. Further, the V / f control means 17 inputs the detected value I of the input current of the inverter device 10 from the current sensor 22.

Next, the operation of this embodiment configured as described above will be described with reference to the flow charts of FIGS.

During operation of the compressor 1, the inverter frequency determining means 16 inputs the room temperature Ta and the set temperature Ts to calculate a deviation (Ts-Ta), and based on the calculation result, a determination signal regarding the inverter output frequency f. V / f
It is output to the control means 17 and the low frequency area discrimination means 18 (step 1). The low frequency region determination means 18 determines whether or not the frequency f is within the low frequency region by comparing this frequency f with a predetermined set value Fs (step 2), and the determination is made. The signal is output to the V / f control means 17. Then, the V / f control means 17
The inverter unit 13 is controlled so that the frequency f and the standard inverter output voltage V corresponding to the frequency f are obtained (step 3).

If it is determined in step 2 that f is equal to or less than Fs, that is, if f is in the low frequency region, the V / f control means 17 causes The inverter unit 13 is controlled so that the frequency f and the maximum inverter output voltage Vmax corresponding to the frequency f are obtained (step 5). The V / f control means 17 reads the detected value of the inverter input current I at this time from the current sensor 22 (step 5) and compares this current I with the set value Is to determine whether or not the compressor 1 is locked. It is determined (step 6). Then, if I ≧ Is, it is determined that the lock is generated, and the operation of the inverter device 10 is stopped (step 7).

On the other hand, when I <Is is determined in step 6, the V / f control means 17 changes the inverter output voltage V from the maximum Vmax to the standard V0 (step 8), and reads the current I at that time. At the same time as loading (step 9), this is set in its own memory (step 10). Then, the inverter output voltage V is increased by one step,
(Step 11), the current I at that time is read (Step 12).

Now, the relationship between the inverter output voltage V and the inverter input current I will be described. The relationship between the air conditioning load and the output voltage V and the input current I of the inverter varies depending on the load of the refrigeration cycle as shown in FIG. For example,
When the load of the refrigeration cycle is heavy, the highest efficiency point is the current I1 voltage V0 point with the smallest current, as shown by the curve A. On the other hand, when the load of the refrigeration cycle is light, the highest efficiency point is the point of current I1 'and voltage V-2, as shown by the curve B.

Therefore, the voltage V closest to the highest efficiency point
This can be achieved by following the procedure below.

First, the current voltage V is increased by one step to detect the current I, and when the current value I becomes higher than the current value before the voltage increase, it is on the left side of the center of the curve, It can be seen that when the current value decreases, it is on the right side of the center of the curve. Therefore, if the current increases when the voltage is increased, the highest efficiency point is at the lower voltage,
When the current decreases, the higher voltage has the highest efficiency point. Therefore, if the current increases when the voltage is increased, the voltage is decreased by one step to the point where the current changes from decrease to increase, and the voltage obtained by increasing the voltage by one step from the point where the current changes to increase is the highest efficiency The voltage V is closest to

On the other hand, when the current decreases when the voltage is increased, the voltage is set to 1 up to the point where the current changes from decrease to increase.
The voltage that is increased step by step and decreased by one step from the point of change to increase is the voltage V closest to the highest efficiency point.

Steps 13 to 18 and step 1 of FIG.
3 to 23 show steps for finding the minimum point by using the characteristic curve showing the relationship between V and I.

That is, when the current state is in the curve A where the load of the refrigeration cycle is heavy in FIG. 5, step 8
At 10 to 10, the current value I1 at the standard voltage V0 is stored as I0, and at steps 11 to 13, this standard voltage V0 is stored.
The current value I = I2 when the voltage is changed to V1 which is increased by one step is read.

Then, in step 13, the standard voltage V
Current value I0 (= I1) at 0 and current value I at voltage V1
(= I2) is compared, and if the current increases, the process branches to step 14, and if it decreases, the process branches to step 19.

In the state of the curve A, since I1 <I2, the routine proceeds to step 14, the current value I2 is stored as I0, and the voltage is changed from the current voltage V1 to V0 which is one step lower. Now read the current again in step 16,
In step 17, the current value I = I1 at this time and the previously stored I
Compare 0 = I2. Since I <I0 in this comparison, the flow returns to step 14 to decrease the voltage by one step, and the comparison result of step 17 is (memory current I0) <
It is repeated until (detection current I) is reached. In the state of the curve A, the voltage V-1 is such that (memory current I0) <(detection current I).

When the comparison result in step 17 is (memory current I0) <(detection current I), it is judged that the voltage closest to the highest efficiency point is one step too far, and step 18 increases the voltage by one step. Let me step 2
Then, the process proceeds to 4 and the voltage change is completed. As a result, curve A
Then, it is determined that the voltage V0 returned by one step from the voltage V-1 is the voltage closest to the highest efficiency point.

On the other hand, in step 13, (memory current I
When 0) ≧ (detection current I), it is determined that the highest efficiency point is in the voltage direction higher than the reference voltage V0, and in this case, steps 19 to 23 are executed.

As described above, when the V / f control means 17 finds the value of the inverter output voltage V that can minimize the inverter input current I, and outputs the voltage signal V and the frequency signal f to the inverter unit 13. The timer 19 starts the measurement (step 24). Then, when it is determined that the predetermined time (for example, 10 to 15 minutes) has elapsed (step 25), the operations after step 1 are repeated again.

As described above, in the configuration of FIG. 1, when operating in the low frequency region, the inverter output voltage is increased every 10 to 15 minutes to determine whether or not compressor lock has occurred. However, for most of the time, since the inverter output voltage that minimizes the inverter input current is used for operation, the power consumption can be reduced,
Power loss can be effectively reduced. Also, since the inverter output frequency is not unnecessarily increased,
The comfort of indoor air conditioning is not impaired.

In the above embodiment, the change of the voltage V in FIG. 5 has been described as being changed stepwise, but it may be changed continuously.

[0039]

As described above, according to the present invention, when operating in the low frequency region, control is performed with the inverter output voltage such that the inverter input current is minimized to determine whether or not a compressor lock has occurred. Since the inverter output voltage is set to increase every predetermined time, the power loss can be effectively reduced without impairing the comfort of the indoor air conditioning.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of FIG.

FIG. 3 is a flowchart for explaining the operation of FIG.

FIG. 4 is a characteristic diagram for explaining the operation of FIG.

5 is a characteristic diagram for explaining the operation of FIG.

FIG. 6 is a characteristic diagram for explaining a conventional example.

FIG. 7 is a characteristic diagram for explaining a conventional example.

[Explanation of symbols]

 1 Compressor 9 Compressor Motor 10 Inverter Device 16 Inverter Frequency Determining Means 17 V / f Control Means 18 Low Frequency Region Discriminating Means V Inverter Output Voltage f Inverter Output Frequency I Inverter Input Current

Claims (2)

[Claims] 1. An air conditioner that performs variable speed control of a compressor motor by controlling an inverter output voltage and an inverter output frequency of an inverter device, and compares the value of the inverter output frequency with a preset value. The low-frequency region determining means for determining whether the value is in the low-frequency region, and the compressor motor being overexcited when the low-frequency region determining means determines that the value is in the low-frequency region. The detected value of the inverter input current when the inverter output voltage is increased so as to be in a state is compared with a preset set value, and when the detected value is equal to or larger than this set value, the operation of the inverter device is stopped. When a command is output, but the detected value is below this set value, it is at least lower than this comparison. Air conditioner, wherein the V / f control means for outputting a command to perform the operation of the inverter device according to the inverter output voltage of Le predetermined time, further comprising a. 2. The air conditioner according to claim 1, wherein the V / f control means continuously or stepwise increases or decreases the inverter output voltage when the detected value is below the set value. By doing so, a minimum value or a value near the minimum value of the detected value of the inverter input current is obtained, and the inverter output voltage corresponding to the minimum value or a value near the minimum value is used to operate the inverter device for a predetermined time. An air conditioner characterized by outputting a command.