JPH07103554A - Current controlling method for air-conditioner - Google Patents

Abstract

PURPOSE:To prevent exceeding of an upper limit value by varying a motor speed by a specific varying speed when number of revolutions of a motor is different from a designated target value, so controlling as to become an objective value, and reducing the varying speed of the number of revolutions and the objective value when power consumption of an conditioner or a motor reach a specific restraint range. CONSTITUTION:An allowable current of a motor 43 of a compressor is set to a value decided by a current capacity of a power breaker such as 20A, a reference current is set to 19.8A by considering a minimum capacity control width of the compressor such as 0.1Hz, and this 19.8-20A is set to a current restraint range. A microcomputer 41 fetches an operating current to be detected by a current detector 40, and decides whether it falls within the restraint range or not. When it falls within the range, a frequency objective value is lowered by a specific control width such as 0.1Hz, and the objective value is set to a fully upper limit value having high resolution. When power consumption of an air conditioner or a motor 43 reaches the restraint range, the control width is reduced, and the objective value is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current control method for an air conditioner, and in particular, it controls the current so that it does not exceed an allowable upper limit of the current, and even when it is overloaded, the current is at the limit of the upper limit. The present invention relates to an operable current control method.

[0002]

2. Description of the Related Art Generally, there is a certain limit to the usable current capacity depending on the installation environment of an air conditioner. For example, in a general household, the current capacity is usually 15 [A] or 20 [A] even if a dedicated power breaker is used. For this reason, when the load of the air conditioner becomes large and the operating current exceeds the current capacity of the power breaker, the power breaker becomes differential, which is inconvenient in use.

Therefore, the operating current of the air conditioner is detected,
In order to prevent the detected value from exceeding the current capacity of the power supply breaker, the capacity of the air conditioner is lowered to control the operating current (most of which is the current consumed by the compressor). As an example of this current control, for example, the current control method described in Japanese Patent Publication No. 2-620 is known.

This conventional method is specifically applied to an air conditioner driven by an inverter system, and the region of the current value supplied from the commercial power source to the air conditioner is divided into a plurality of current zones. , The current value supplied from the commercial power supply to the air conditioner is detected, and if this detected current value is in the high current control zone, the output frequency of the frequency converter is decreased by a predetermined value every predetermined time to detect the detected current. When the value is in the intermediate zone of the current control zone, the output frequency of the frequency converter is not increased, and when it is in the low zone of the current control zone, the output frequency of the frequency converter is increased or decreased by a predetermined value at predetermined time intervals. A method is adopted in which the output frequency is automatically controlled to reach the target value.

[0005]

However, in the current control method described in Japanese Patent Publication No. 2-620 mentioned above,
Multiple current control zones (power breaker current capacity 1
5 [A]), A zone of 15 [A] or more, 15 to 15
When the detected current value enters the A zone, for example, the frequency of the current given to the compressor every 30 seconds, for example, the B frequency zone of 14 [A] and the C zone of 14 [A] or less. Although it is intended to perform frequency down control in which the frequency is lowered by 5 Hz, the B zone as the current regulation area is very rough. That is, the B zone is 14 to 1
Since it is 5 [A], it is assumed that the operation at 14.5 [A] continues, for example. As an air conditioner, near the upper limit of 14.9 [A], or 15
[A] If it can be operated exactly, the maximum air conditioning capacity can be exhibited within the allowable range. However, the method described in the above publication guarantees that the maximum air conditioning capacity within the allowable range can be exhibited under an overloaded condition. In some cases, the air conditioning capacity was surplus.

Further, the current control method described in the above publication is in the current control mode in which the frequency rise is forcibly prohibited or lowered so that the operating current does not exceed the allowable current (current capacity of the power breaker). There is no need for forced control, and what is the relationship between the frequency control width in both states when operating at a frequency (compressor speed, that is, the air conditioning capacity of the air conditioner) that is simply dependent on the room temperature? Not listed. For this reason, if the frequency control width that emphasizes control responsiveness is set, the control accuracy will be inevitably lowered. Conversely, if the frequency control width with high resolution is set in order to improve control accuracy, the response of the normal control will be reduced. There is a problem of poor sex.

The present invention has been made in view of such a conventional problem, and in particular, the operating current of the air conditioner is controlled so as not to exceed an upper limit value determined by the current capacity of the power breaker, and an overload is generated. Or, even in the case of heavy load, the purpose is to enable operation at a current value close to the upper limit value.

[0008]

In order to achieve the above object, the current control method for an air conditioner according to the present invention comprises a refrigeration cycle using a compressor, a condenser, a pressure reducing device, and an evaporator. In a current control method for controlling an operating current of an air conditioner configured to use an electric motor as a drive source of a compressor and automatically adjusting the rotational speed of the electric motor according to an air conditioning load, the rotational speed of the electric motor is designated. Enter the target value,
When the rotation speed of the electric motor is different from the target value, the rotation speed of the electric motor is changed at a predetermined change speed to control the rotation speed of the electric motor to reach the target value, and the air conditioner or the electric power consumption of the electric motor is reduced. When the electric power reaches a predetermined regulation range, the changing speed of the rotation speed when changing the rotation speed is changed small, and the target value is lowered.

[0009]

When the allowable current is a value determined by the current capacity of the power breaker, for example, 20 [A], the current regulation range is
For example, from a predetermined value around 19.8 [A] to an upper limit value of 20
The range is up to [A]. Operating current (mostly consumed by the compressor) does not fall within this current regulation range During normal operation (operating current does not exceed the upper limit value 20 [A])
Is increased or decreased so that the frequency command value follows the frequency target value in the first control width (for example, 1 [Hz]), and high responsiveness of the air conditioning capacity control is secured. On the other hand, if the air conditioning load becomes heavy and it is determined that the operating current is within the current regulation range, it is determined that current limitation is necessary, and the frequency target value is set in the second control range (for example, 0.1 [Hz]). Can be lowered. As a result, the target value is set to the limit with high resolution, so even when the operating current is likely to exceed the allowable current,
It is possible to operate with the current value at the limit of the allowable current, and maximize the air conditioning capacity within the allowable range.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An air conditioner according to an embodiment of the present invention will be described below with reference to FIGS.

First, the refrigerant circuit of the air conditioner will be described with reference to FIG.

In FIG. 1, reference numeral 1 is a hermetic compressor having a three-phase induction motor and a compressor body driven by the electric motor, and 2 is a sound generated from a refrigerant discharged from the compressor 1. The muffler 3 for reducing the air flow is a four-way valve that changes the direction of the refrigerant flow during cooling / heating operation.
Is a heat source side heat exchanger, 5 is a capillary tube (pressure reducing device), 6 is a screen filter, 7 is a use side heat exchanger,
8 is a muffler, 9 is an accumulator, and 10 is a solenoid valve.

Depending on the switching position state of the four-way valve 3 and the open / close state of the solenoid valve 10, the flow of the refrigerant discharged from the compressor 1 is in a solid arrow state (refrigerant operation) and a dotted arrow state (heating operation). And the state of a solid arrow with a dot (defrosting operation). During the cooling operation, the heat source side heat exchanger 4 acts as a condenser, and the use side heat exchanger 7 acts as an evaporator. On the other hand, during the heating operation, the use side heat exchanger 7 acts as a condenser, and the heat source side heat exchanger 4 acts as an evaporator. Further, during the defrosting operation, a part of the refrigerant discharged from the compressor 1 in the refrigerant flow during the cooling operation is directly supplied to the heat source side heat exchanger 4 to raise the temperature of the heat exchanger 4. The heat exchanger 4 is defrosted.

FIG. 2 shows an example of the control circuit of this air conditioner. The circuit on the left side of the one-dot chain line drawn in the center of the figure is the control circuit mounted on the indoor unit A, and the circuit on the right side is the control circuit mounted on the outdoor unit B. Both control circuits are the power line 100 and the communication line 200. Connected to each other.

The control circuit of the indoor unit A has a plug P
AC 100 [V] supplied from G is supplied to the rectifier circuit 11 and
A motor power supply circuit 12 that changes the voltage of DC power applied to a DC fan motor (brushless motor) (M1) 16 that sends cold and warm air to the room between 10 and 36 [V] according to a signal from the microcomputer 14, and a microcomputer. The power supply circuit 13 for generating a DC voltage of 5 [V] for 14 and the energization of the stator winding of the DC fan motor 16 in response to a signal from the microcomputer 14 based on the rotational position information of the DC fan motor 16. A switch board 17 provided with a motor drive circuit 15 for controlling timing, an ON / OFF switch provided on the operation panel of the indoor unit A, a trial run switch, and the like.
And the remote control signal (ON
18a for receiving the ON / OFF signal, the switching signal for cooling / heating, the room temperature set value signal, etc., the display plate 18 for displaying the operating state of the air conditioner, and the flap for changing the blowing direction of the cold / hot air Flap motor (M2)
And 19 are provided.

Further, a room temperature sensor 20 for detecting room temperature.
A heat exchanger temperature sensor 21 for detecting the temperature of the indoor heat exchanger, and a humidity sensor 22 for detecting the indoor humidity.
Converted and captured. The control signal output from the microcomputer 14 to the outdoor unit B is transmitted via the serial circuit 23 and the terminal board T3. In addition, a triac 26 is transmitted via the driver 24 by a signal from the microcomputer 14.
Also, the heater relay 27 is controlled, so that the energization of the reheating heater 25 during dehumidification is phase-controlled.

Further, reference numeral 30 in the indoor unit A indicates an external ROM (Read Only Memory) in which unique data for specifying the model and various characteristics of the air conditioner is stored. The unique data is fetched from the external ROM 30 immediately after the power is turned on and immediately after the operation is stopped. External RO at power on
Until the unique data is fetched from M30, the command input from the wireless remote controller 60, the operation described later, and the state of the test operation switch are not detected.

Next, the control circuit of the outdoor unit B will be described.

The outdoor unit B is connected to the terminal plates T1, T2 and T3 of the indoor unit A, respectively.
'1, T'2 and T'3 are provided. Reference numeral 31 is a varistor connected in parallel to the terminal plates T1 and T2, 32 is a noise filter, 34 is a reactor, 35 is a voltage doubler circuit for forming a voltage doubler, and 37 is a smoothing circuit. This gives 10
A DC voltage of about 280 [V] can be obtained from an AC voltage of 0 [V].

Reference numeral 39 is a serial circuit for converting the control signal transmitted from the indoor unit A through the terminal board T'3 and sending it to the microcomputer 41, and 40 is a current supplied to the load of the outdoor unit B. Is a current detection circuit which detects the current by the current transformer (CT) 33 and sends it to the microcomputer 41, 41 is a microcomputer, and 42 is a switching power supply circuit for generating a power supply voltage of the microcomputer 41. Further, reference numeral 38 is a motor drive circuit that performs PWM control of energization to the electric motor 43 (three-phase induction motor) of the compressor 1 based on a control signal from the microcomputer 41. The motor drive circuit 38 constitutes a so-called inverter device in which six power transistors are connected in a three-phase bridge shape. Reference numeral 44 is a discharge temperature sensor that detects the refrigerant temperature on the discharge side of the compressor, and 45 is a fan motor that regulates the speed to the third speed, which blows air to the outdoor heat exchanger. Four
Reference numerals 6 and 47 are four-way valves and solenoid valves for switching the flow path of the refrigerant.

Further, the outdoor unit B is provided with an outside air temperature sensor 48 for detecting the outside air temperature near its intake port. Further, a heat exchanger temperature sensor 49 for detecting the temperature of the outdoor heat exchanger is provided. These detected values are taken into the microcomputer 41 as digital values.

The outdoor unit B is also provided with an external ROM 60, and the unique data of the outdoor unit B is stored in this external ROM 60.

The symbol F of both units A and B is a fuse. The microcomputer has a configuration in which a ROM storing a program, a RAM storing reference data, and a CPU executing the program are housed in the same package (for example, 87C196MC (MCS manufactured by Intel Corp.
-96 series)).

Next, the current detection circuit 40 mounted on the outdoor unit B will be described with reference to FIG.

This current detection circuit 40 is used in the outdoor unit B.
Connected to a current transformer 33 that detects a current flowing through the current transformer 33 in a non-contact manner, and a resistor 91 connected to a secondary side of the current transformer 33,
It is composed of voltage dividing resistors 92a and 92b. The voltage at the output terminal a of the current transformer 33 is directly A /
It is supplied to the D port. The microcomputer 41 takes in the supplied voltage data at a cycle of 500 μsec.

A voltage of +5 [V] is applied across the series circuit of the voltage dividing resistors 92a and 92b. Resistor 92a,
Since both 92b have the same resistance value, the resistors 92a,
92b intermediate connection point, that is, the output terminal b of the current transformer 33
Is applied with a voltage of +2.5 [V].

The voltage at the output terminal a of the current transformer 33 is +2.5.
2.5 above and below the boundary of [V] (voltage of output terminal b)
Amplitude variation by [V] and plus 2.5
The resistance value of the resistor 91 is set so that the current peak value corresponds to 30 [V] when it is [V]. Therefore, a voltage varying between 0 and 5 [V] is supplied to the A / D port of the microcomputer 41.

FIG. 4 shows a voltage waveform (voltage waveform corresponding to current) applied to the microcomputer 41. It is a sine wave that swings up and down about +2.5 [V] (no distortion). This voltage change is A / D converted in a cycle of 500 μsec and stored as digital data in the microcomputer.

FIG. 5 is a schematic flowchart of current calculation executed by the microcomputer 41.

When the power switch (not shown) of the air conditioner is turned on, the current calculation shown in FIG. 5 is started. First, initialization is carried out (S-1), and a timer built in the microcomputer 41 starts counting time. Then, in step S-2, 500 μs
While ec does not elapse, the current is controlled based on the actual current value I (S-7: refer to the process of FIG. 6 described later), a PWM (pulse width modulation) signal is generated (S-8), and other control is performed. (S-9). However, in step S-2, 500 μse
When c has passed, the already stored Dn is replaced by Dn + 1
(S-3) (n is changed from 0 to 200), the voltage value of the output terminal a of the current transformer 33 is fetched as current data, and the digital value of the voltage applied to the microcomputer 41 is converted into a sine wave. The absolute value of the value obtained by subtracting 2.5 [V] which is the center is set as Do (S-4). As a result, the upper and lower amplitudes of the current can be full-wave rectified and captured. In addition,
At the start of operation, current calculation is not performed until 200 pieces of data Dn have been fetched (S-5), and after 200 pieces of data have been fetched, current calculation is performed by the following formula 1.

[0031]

[Equation 1] By the above current calculation, the actual current value I (substantially equivalent to the effective value) is obtained every 500 μsec. n = 200
By setting to, it is possible to obtain an average value for 6 cycles with an alternating current of 50 Hz and an average value for 5 cycles with an alternating current of 60 Hz.

In the example of FIG. 5, the current is calculated every 500 μsec, but it may be calculated every 200 msec.

FIG. 6 shows a frequency command value Fo (when the three-phase AC power is supplied to the compressor 1 based on the actual current value I, which is the current control executed in step S-6 in FIG. 5). It is a flowchart which correct | amends rotation speed.

In this embodiment, the operating current range of the air conditioner is set to "TRIP" and "DOW" as shown in FIG.
It is divided into three stages of "N" and "NORMAL". "TR
"IP" is the allowable current 20 determined by the power breaker
This is a current region exceeding [A] (upper limit value). "DOW
"N" is equal to or less than the allowable current 20 [A], but is in a region (corresponding to the current regulation region of the present invention) which is fairly close thereto, and is a current region between the allowable current 20 [A] and the reference current Is. . In this embodiment, the minimum capacity control width of the compressor (0.
The reference current Is is set to 19.8 [A] in consideration of 1 Hz), but it is not necessarily limited to this value, and when the allowable current is 15 [A], for example, Is = 14.8.
It may be set to [A]. A differential is set for the reference current Is in consideration of the hysteresis characteristics of the state in which the actual current value I is increasing and the state in which the actual current value I is decreasing. Furthermore, "NORMAL" is a region below the reference current Is, and indicates a current region in which normal operation without current limitation is possible.

Now, the processing of FIG. 6 will be sequentially described.

The microcomputer 41 of the outdoor unit B determines whether the actual current value I falls within the "TRIP" region shown in FIG. 7 (S-20). When it enters the "TRIP" region, the operating current exceeds the allowable current 20 [A] and it is recognized that the power breaker will be dropped, and the frequency command value Fo of the three-phase AC power supplied to the compressor is forcibly set to zero. (S-21).

On the other hand, when the actual current value I does not fall within the "TRIP" area, it is determined whether the value I falls within the "DOWN" area (S-22). Here, when it is determined that the frequency target value F falls within the "DOWN" region, the frequency target value F is forcedly set to a fine control width (corresponding to the second control width of the present invention) of 0.
Decrease by 1 [Hz] (S-22). In other words, in this state, even if the indoor unit A commands the frequency target value F of the normal control width in steps of 1 Hz according to the set temperature or the like, it is ignored and the current limit is given priority, and the target value is The step of F is finely lowered by 0.1 [Hz].

However, when it is determined in step S-22 that the actual current value I is not within the "DOWN" region, the actual current value I is within the "NORMAL" region, so current limitation is not necessary. At this time, the frequency target value F is the frequency Ft transmitted from the indoor unit A through the communication line.
(S-24).

Then, at this time, the frequency command value Fo actually supplied to the compressor 1 is compared with the frequency target value F (S-25, 27). As a result, if F> Fo, the frequency command value Fo is raised by 1 Hz which is the normal adjustment width (corresponding to the first control width of the present invention) (S-26), and F ≦ F.
If o, then F <Fo is determined (S-27). As a result, if F <Fo, the frequency command value is lowered by the normal adjustment width of 1 Hz (S-28). When F = Fo, the command value Fo naturally remains unchanged.

By thus obtaining and supplying the frequency command value Fo, the actual value of the operating current I is controlled to a value corresponding to the command value Fo through the processing of step S-8 in FIG.

Particularly, in this embodiment, the current transformer 3
Since the current is detected by the method of directly capturing the output of No. 3 into the microcomputer 41, the fluctuation of the operating current can be detected by the actual value without any delay, and the approximate current value after being smoothed by the conventional capacitor. It is possible to detect with much higher accuracy and with higher response than the current detection of the method using.

Therefore, the reference current Is that defines the "DOWN" region can be set to a value as close as possible to the allowable current of 20 [A]. As a result, since the "NORMAL" region is expanded, even if the air conditioning load increases, the current limiting state is unlikely to occur, and the desired air conditioning operation can be performed with a value very close to the allowable current 20 [A].

When the air conditioning load further increases and the actual current value I of the operating current enters the "TRIP" region, the rotation stop of the compressor is immediately instructed. When it is confirmed that the rotation speed has decreased due to this stop command and the actual current value I has entered the "DOWN" region, this time the frequency is finely reduced in 0.1 [Hz] steps (down of the target frequency value F). Command.

As described above, when the frequency is reduced, the frequency is controlled more finely than in the normal state, so that the operation can be performed while maintaining the actual current value I at the margin of the permissible current immediately after returning to the "DOWN" region. That is, the actual current value I = 19.9 [A]
Alternatively, it can be operated at a value just below the upper limit of whether I = 20 [A]. Therefore, unlike the case where the frequency is lowered at the control width of 1 [Hz], which is the same as in the normal state, the frequency down control can be operated in the state close to the maximum capacity corresponding to the allowable current when the load is heavy or overloaded. This allows
Although the current is limited, the capacity of the air conditioner can be maximized within the allowable range.

On the other hand, in this embodiment, since the frequency control width (the step size of the increase / decrease of the frequency command value) is separately used in the normal operation and the current limitation, the high responsiveness in the normal operation and the current limitation are set. There is also an advantage that high resolution (control accuracy) is compatible.

In the above embodiment, the position of the current transformer for detecting the load current is set to the midway position to reach the compressor of the outdoor unit, but the present invention is not limited to this. Most of the electric current of the air conditioner is consumed for driving the compressor, so such a mounting position is used for convenience. However, for example, the line on the power plug side of the indoor unit may be used,
Further, it may be a line of a power breaker attached to this air conditioner.

In the above embodiment, the case where the number of indoor units is one has been described, but it may be applied to a multi-type air conditioner having a plurality of indoor units. Furthermore, although the indoor unit power supply type has been described, it can be applied to the outdoor unit power supply type.

Although the three-phase induction motor is used as the drive source of the compressor in the above embodiments, a DC motor may be used as the drive source of the compressor. In this case, the frequency may be replaced by the voltage in the above-described embodiment, and the ability adjustment performed by changing the frequency may be changed to adjust the ability by changing the voltage. Further, in the case of a DC brushless motor, if the motor drive circuit 38 is used, the DC motor can be easily used if the microcomputer 41 switches the energization to the stator winding instead of generating the PWM waveform.

Needless to say, at this time, the same effect as that obtained by using the induction motor can be obtained.

[0050]

As described above, according to the operation control method of the air conditioner according to the present invention, the frequency target is set according to the room temperature or the like during the normal operation in which the operating current does not reach (do not enter) the current regulation region. The value is set, the frequency command value is increased or decreased in the first control width (for example, 1 [Hz]) so as to follow this target value, the air conditioning load becomes heavy, and the operating current enters the current regulation range. If it is determined that the current limit is required, the second control width (for example, 0.1
Since the target frequency value can be lowered at [Hz]), high responsiveness of control can be secured during normal operation, and the air conditioning capacity can be maximized within the allowable range even during operation in the current limit state, and the power breaker can be used. A good air-conditioning environment can be obtained without dropping it.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a control circuit diagram of the air conditioner of the embodiment.

FIG. 3 is a circuit diagram of a current detection circuit.

FIG. 4 is a waveform diagram of an output voltage of a current detection circuit.

FIG. 5 is a schematic flowchart showing current calculation by a microcomputer.

FIG. 6 is a schematic flowchart showing correction processing of a frequency command value by a microcomputer.

FIG. 7 is an explanatory diagram showing up and down of an operating current corresponding to a current region.

[Explanation of symbols]

 A outdoor unit B indoor unit 1 compressor 4 heat source side heat exchanger 5 capillary tube (pressure reducing device) 7 use side heat exchanger, 33 current transformer 38 motor drive circuit 41 microcomputer 42 switching power supply 43 compressor electric motor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazunobu Hosokai 2-18 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Yoshinori Nakayama 2-18, Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. Incorporated (72) Inventor Kenji Shimizu 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A refrigeration cycle is configured using a compressor, a condenser, a decompression device, and an evaporator, an electric motor is used as a drive source of the compressor, and the rotation speed of the electric motor is automatically adjusted according to an air conditioning load. In the current control method for controlling the operating current of the air conditioner configured as described above, a target value that specifies the rotation speed of the electric motor is input, and when the rotation speed of the electric motor is different from the target value, at a predetermined change speed. When changing the rotation speed of the electric motor to control the rotation speed of the electric motor to reach a target value, and changing the rotation speed when the power consumption of the air conditioner or the electric motor reaches a predetermined regulation range. Current control method for controlling the operating current of an air conditioner, characterized in that the speed of change of the number of revolutions of the air conditioner is reduced and the target value is lowered.