JPH02203142A - Air-conditioner - Google Patents

Abstract

PURPOSE:To widen the range of an operation frequency by a method wherein the value of a detective operation current is obtained at every prescribed sampling time, while this value and a value obtained at the last time are subjected to computation to calculate the rate of increase of the current value, and this rate of increase is compared with a value stored beforehand in an internal memory or the like. CONSTITUTION:An operation current detecting element 10 which includes a detecting sensor 9 for detecting a primary-side current (operation current) between a noise filter element 2 and an AC-DC converter element 4 and obtains an operation current value by converting the detected current into a voltage, an overcurrent detecting element 11 which converts a detected current by a shut resistance 6 into a voltage and obtains its current value (overcurrent value), and a control element 12 which outputs a pulse signal for switching to a transistor of a power transistor element for subjecting a compressor 8 to an inverter control and executes stopping of the inverter control on the basis of the detected values of the operation current and the overcurrent, are provided. Besides, an air-conditioner has an operation current suppressing function etc. In the control element 12, the value of the aforesaid primary- side current is compared with a regulating value set beforehand, and when it exceeds this value, the operation current is suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an air conditioner in which a load (compressor) is controlled by an inverter, and more specifically, the invention relates to an air conditioner in which a load (compressor) is controlled by an inverter. The present invention relates to an air conditioner that detects this and stops invar control when the lock state is reached.

[Conventional Example] Conventionally, this type of air conditioner has various protection functions, such as a function to protect against overcurrent caused by locking of the compressor. This overcurrent protection function turns off all switch data applied to the power transistor when the DC current supplied to the power transistor that drives the compressor exceeds a preset regulation value. Power to the compressor is stopped to prevent compressor overcurrent.

Therefore, if the compressor becomes locked, no voltage is applied to the compressor, or in other words, the compressor power supply is shut off (current trip operation), resulting in damage to the compressor and power transistor section. etc. can be prevented.

[Problem to be solved by the invention] By the way, the inverter control in the above air conditioner is as follows:
Digital sine wave approximation PWM()'ulse Wi
dth Modulation) method to process the waveform of the AC V4 source, and as shown in the ■/de characteristic diagram in Figure 4, in order to keep the torque of the compressor motor constant, the frequency F and voltage ■ are simultaneously converted, and V /F is kept constant. Further, as shown at point A in the figure, during inverter control, when the operating frequency is at the lowest value of 1, voltage v1 is applied to the compressor. At this time, when the compressor becomes locked, the detected value IA of the DC current supplied to the power transistor section exceeds the regulation value IT, as shown at point 0 in FIG. 5, and the overcurrent protection The function will work. Conversely, the minimum operating frequency 1.゛ must be such that the detected current IA exceeds the regulation value IT when, for example, the compressor is in a locked state in the inverter control of the frequency F machine. .

However, in the above-mentioned overcurrent protection function, as shown at point B in Fig. 4, the lowest operating frequency of the compressor is Fa (< F
l), the voltage of the compressor will naturally be Va (<V□). At this time, if the compressor becomes a locked layer, the fifth
As shown at point D in the figure, the detected current is the regulation value I? As a result, the above-mentioned overcurrent protection function will not operate. Therefore, in the air conditioner having the above-mentioned overcurrent protection function, the value of the minimum operating frequency is limited.

On the other hand, in an air conditioner, if the operating frequency can be set over a wide range, fluctuations in indoor temperature can be suppressed and comfort can be further improved. For this purpose, it is necessary to lower the value of the minimum operating frequency, but from the above-mentioned point, it has not been possible to lower the minimum operating frequency.

This invention was made in view of the above-mentioned problems, noting that the locked state of a compressor can be detected by a sudden change in operating current, and its purpose is to widen the range of operating frequencies. To provide an air conditioner capable of improving indoor comfort.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides a primary current (
In an air conditioner that is equipped with an operating current detection means for detecting the operating current (operating current) and suppresses the operating current so that the operating current does not exceed the rated value due to overload operation etc. when controlling the load with an inverter, ! calculation means for calculating the rate of increase in the operating current by comparing the operating current detected by the rotating current detection means and the operating current detected last time;
If the increase rate is larger than a preset value, it is determined that the compressor is in a locked state, and an OFI° signal is applied to each transistor of a power transmitter section that applies voltage to the compressor; A control means for stopping the inverter control is provided, and the inverter control is stopped when the compressor is in a locked state.

[Function] With the above configuration, when the compressor is controlled by the inverter, the primary side current (operating current) of the air conditioner is detected in the operating current detection means, and the control section of the calculation means and control means ( The microcomputer obtains the value of the detected operating current at every predetermined sampling time, calculates the increase rate of the current value by calculating the value and the value obtained in the previous question, and stores the increase rate and the internal memory in advance. The detected current is compared with the stored value, and it is determined whether the detected current is rapidly increasing. Note that when the compressor is in a locked state, the primary side current (operating current) increases sharply, so the amplification factor thereof is obtained in advance and stored in the internal memory. As a result, if the control unit determines that the amplification factor of the detected operating current exceeds the value stored in its internal memory, it applies voltage to the compressor in order to stop the inverter control. An OFF signal is given to each transistor in the power transistor section.

[Implementation example] Embodiments of the present invention will be described below based on the drawings.

In Fig. 1, an AC base [1] supplied to an air conditioner passes through a noise filter section 2 and a power factor improvement reactor 3, is voltage-doubled and rectified by an A-DC-DC converter section 5, and is converted into a direct current. Ru. This converted DC power source is smoothed by a large capacity capacitor 5 which also serves as a low frequency noise filter, and is supplied to a switching power transistor section 7 controlled by an inverter via a shunt resistor 6 for overcurrent detection of the transistor. - Voltage is applied to the compressor 8 by turning on and off the transistor of the transistor section 7.

The air conditioner also includes the noise filter section 2 and an AC
- An operating current detection unit 1 that includes a current sensor (CT) 9 for detecting the primary side current (operating current) between the DC converter unit 4 and converts the detected current into a voltage to obtain an operating current value.
0, an overcurrent detection unit 11 that converts the current detected by the shunt resistor 6 into voltage and obtains the current value (overcurrent value), and a transistor of the power transistor unit 7 for inverter control of the compressor 8. A control section (microcomputer) 12 is provided which outputs switching pulse signals and stops inverter control based on the detected values of the operating current and overcurrent. In addition,
Upper JL! The air conditioner has an operating current suppression function, etc., in which the control unit 12 compares the primary current value with a preset regulation value, and when it exceeds the regulation value, the operating current is suppressed, and the operating current becomes normal. Make sure not to exceed the rating of the breaker used at home.

Next, the operation of the air conditioner having the above configuration will be explained based on the flow chart of FIG. 2 and the time chart of FIG. 3. Note that the control unit 12 has the operating current increase rate H obtained in advance when the compressor is in the locked state, and stores it in the internal memory (
(not shown).

First, in the control unit 12 of this air conditioner, the compressor is inverter-controlled according to the operating frequency according to the operating command (
Step 5TI), then in the operating current detection unit IO, for example, the time constant C-R of the circuit that detects the primary current and converts it into a DC voltage is lk (Ω) x 100 (μF) =
100 (m100), the control unit 12 sets the sampling time (t) of the detected operating current by the operating current detection unit 10 to 100 (msec) or more, for example, 200 msec.
This is performed every (msec) (step ST 2 ). Then, at every predetermined time period t = ZOO (msec), the operating current value is calculated, compared with the previously calculated value, and the rate of increase for f4 operations is calculated (step 5T3).

That is, when the compressor is controlled by the inverter according to the operation command, if the operating current changes as shown by the solid line in Fig. 3, in 'r□, the previously detected operating current and the same detection The increase rate is calculated from the difference in operating current.

Subsequently, it is determined whether the calculated increase rate of the operating current is greater than or equal to a predetermined value H, that is, whether it has increased by a certain value or more than the previously detected operating current value (step 5T4). That is, it is determined whether or not the compressor 8 is in the locked state. When the rate of increase is not H or more, it is determined that the compressor 8 is not in the locked state, and the process returns to step S'rl, where inverter control is performed in accordance with the operation command. If such inverter control is continued, as shown in Fig. 3, T,,'1°
,.

The rate of increase in the operating current is calculated every '1m, T, and it is determined whether the rate of increase is greater than or equal to H.
Detection of lock status is performed. and.

As shown at point X in FIG. 3, when the compressor 8 becomes locked for some reason between 'l' 6 and 17, the operating current increases rapidly. Then, at the 1'77 timing of the third Y point, the calculated rate of increase becomes H or higher (step 5T4), so the inverter control is stopped (step 5T5).

That is, the control section 12 outputs a signal that turns all the transistors of the power transistor section 7 into OF)I', and no voltage is applied to the compressor 8.

That is, as explained in FIGS. 4 and 5, when the compressor 8 is in the locked state, the operating frequency is too low,
If the current value detected by the overcurrent detection unit ti does not exceed the regulation value (current trip operation value), the operating current detected by the operating current measurement unit lO changes rapidly, so that the locked state is not detected. , the inverter control of the compressor 8 can be stopped.

In this way, even if the operating frequency is low, the locked state of the compressor 8 can be detected, so the frequency of inverter control can be controlled over a wide range.

Note that the above air conditioner also has the same protection function as the conventional one, but a description thereof will be omitted.

[Effects of the Invention] As explained above, according to the present invention, in an air conditioner in which a load compressor or the like is controlled by an inverter, an operating current detection means for detecting the primary current and a detected operating current value are provided. It is obtained at regular intervals, and the current detected operating current value is compared with the previous detected operating current value to determine whether it has increased by a predetermined value or more. We have provided a calculation means for determining the operating current, and a control means for stopping the inverter control if the rate of change in the operating current value exceeds the value when detecting the operating current, so even if the operating frequency of the compressor is low, the Since the locked state of the compressor can be detected, the frequency of the inverter control can be widened, which has the effect of improving indoor comfort.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of an air conditioner showing an embodiment of the present invention, FIGS. 2 and 3 are a flow chart and a time chart for explaining the operation of the air conditioner, and FIG. 5 is a V/F characteristic diagram for explaining inverter control in an air conditioner, and FIG. 5 is a diagram for explaining a protection function in a conventional air conditioner. In the figure, 1 is an AC power supply, 6 is a shunt resistor, and 7 is a power supply.
transistor section, 8 a compressor, 9 a current sensor (C'!
'), 10 is an operating current detection section, 11 is an overcurrent detection section, 1
2 is a control unit (microcomputer). Patent applicant Fujitsu General Co., Ltd. Representative Patent attorney Takuya Ohara Figure 4 F2 Fl Frequency Figure 5 Voltage

Claims (1)

[Claims] (1) Equipped with an operating current detection means that detects the primary side current (operating current), and suppresses the operating current so that the operating current does not exceed the rating due to overload operation etc. when controlling the load with an inverter. In the air conditioner, a calculation means calculates an increase rate of the operating current by comparing the operating current detected by the operating current detection means and the previously detected operating current, and the increase rate is larger than a preset value. An air conditioner further comprising a control means for stopping the inverter control in some cases.