JPH01222695A - Air conditioner - Google Patents

Abstract

PURPOSE:To restrain the primary input current below a safety value, to evade stop during the operation, and to perform efficient operation by reducing the maximum operation frequency of an electric compressor at the time of input voltage drop on the primary side or at the time of overload. CONSTITUTION:The DC output of an AC/DC conversion circuit 102 is detected by a detection means 101, and varies in proportion with the changes of the voltage of a power source and the load change of an electric compressor. Accordingly, the output of the detection means 101 and the set value 106 are compared by a comparison means 105 and when the output of the detection means 101 is below the set value 106, the primary side input is prevented from becoming an overcurrent by lowering the maximum frequency of a control means 103 to the specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an air conditioner that performs cooling using a refrigerant compression cycle, and particularly relates to an air conditioner whose cooling capacity is adjusted by inverter control.

(B) Conventional technology In this type of conventional air conditioner, when the current to the electric compressor increases due to an increase in the load on the electric compressor or a drop in the input power supply voltage, the negative side input becomes excessive. The system detects current and temporarily stops the compressor to prevent destruction or damage to the inverter control circuit elements and other parts.

(c) Problems to be solved by the invention However, there is a conundrum that if the electric compressor is operated intermittently due to fluctuations in input voltage or load, the operating efficiency as an air conditioner will drop significantly. .

This invention was made in consideration of these circumstances,
By detecting power supply voltage fluctuations and load fluctuations and operating the electric compressor at the corresponding maximum frequency, the electric compressor is prevented from operating intermittently in response to fluctuations in the base N voltage and load. It provides air conditioners.

(d) Means for Solving the Problems FIG. 1 is a block diagram showing the configuration of the present invention, in which 1 inch is a detection means for detecting and outputting the DC output of the A C/DC conversion circuit 102, and 103 is a detection means for detecting and outputting the DC output of the A C/DC conversion circuit 102. DC/AC conversion circuit 104
105 is a detection means l for controlling the output frequency of the
Comparison circuit 107 that compares the output of ot and the set value 106
is the control means 1 when the output of the detection means 1 inch is less than the set value.
This is a setting means for lowering the maximum frequency of the output of 03 to a predetermined value.

(e) Operation In FIG. 1, the DC of the A C/DC conversion circuit 102
The output is detected by the detection means 101, but A C/
The DC output of the DC conversion circuit 102 increases or decreases in proportion to fluctuations in the power supply voltage and the load on the electric compressor. Therefore,
A comparison means 105 compares the output of the detection means 101 and the set value 106.
The output of the detection means 101 is compared with the set value 106.
By lowering the maximum frequency of the control means 103 to a predetermined value when the current is less than 1, the negative side input is prevented from becoming overcurrent. This prevents the air conditioner from being stopped during operation, improving operating efficiency.

(f) Examples The present invention will now be described in detail based on examples shown in the drawings. This invention is not limited by this.

FIG. 2 is a block diagram showing an embodiment of the present invention,
■ is a compressor, 3 is an outdoor heat exchanger, 4 is an indoor heat exchanger, 5
6 is an outdoor blower, and 7 is an indoor blower.

FIG. 3 is an electric circuit diagram showing the control circuit of the embodiment shown in FIG. 2, in which 2 is a single-phase motor connected to the compressor 1 (FIG. 2), 8 is a commercial AC power supply, and 9 is a diode. Bridge DB
9a is a voltage dividing circuit for detecting the output voltage Vd of the rectifying surface path, 10 is an inverter, and the inverter 10 is composed of transistors TRI to T.
It consists of a bridge circuit composed of R4 and a flywheel diode DI-D4, and receives the output of the rectifier circuit 9 and supplies variable frequency AC output to the single-phase electric motor 2.

C2 is a driving capacitor connected to the auxiliary winding of the single-phase electric kuma 2, 11 is a one-chip microcomputer (hereinafter referred to as microcomputer) with built-in ROM, RAM, CPU, etc., and 12 is the microcomputer 11's A transistor drive circuit that receives the output and controls the transistors TRI to TR4, C
T is a current transformer 13 that detects the primary input current of the rectifier circuit 9;
converts the output of current transformer CT into DC and sends it to microcomputer 11? This is the rectifier circuit that inputs this.

The operation in such a configuration will be explained using the flowchart shown in FIG. First, when the air conditioner starts operating (step 201), the transistor drive circuit 12 adjusts the output frequency of the inverter IO, causing the motor 2 to rotate and the compressor 1 to operate. Then, the cooling system shown in FIG. 2 starts operating (step 202). Then, the output voltage Vcl of the rectifier circuit 9 is detected by the voltage dividing circuit 9a (step 2'03), and the set value Vs and voltage Vd are compared in the microcomputer II (step 204). If Vd≧Vs, the maximum frequency fM of the inverter 10 is set to fl (step 205). However, in step 204, vd<V
s, the maximum frequency set value fM is changed to a frequency f2 lower than fl (step 206).

Then, these routines are repeated and the microcomputer l'
When a stop command is output from 1, the operation is stopped (step 207).

Note that even if the maximum frequency set value fM is lowered from fl to f2, if an overcurrent in the primary input is detected by the current transformer CT, the output of the inverter IO is stopped as before.

In this way, in response to changes in the output Vd of the rectifier circuit 9,
Since the maximum frequency of the inverter is set, it is avoided that the primary current becomes overcurrent due to fluctuations in the power supply voltage or load during operation and the operation of the inverter 10 is stopped, and the air conditioner operates efficiently. will be done.

(G) Effects of the Invention According to this invention, the maximum operating frequency of the electric compressor is reduced when the input voltage on the negative side drops or when there is an overload, so the input current on the negative side is suppressed to below a safe value and the compressor is operated. Stopping operations during operation are avoided, resulting in efficient operation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing an embodiment of the invention, and FIG. 3 is an electric circuit diagram showing a control circuit of the embodiment shown in FIG. FIG. 4 is a flowchart showing the operation of the embodiment shown in FIG. ■・・・Compressor, 2...Single-phase electric motor, 3
...Outdoor heat exchanger, 4...Indoor heat exchanger, 5...Pressure reducer, 6.Outdoor blower, 7
... Indoor blower, 8 ... Commercial AC power supply, 9 ... Rectifier circuit, 9a ... Voltage dividing circuit, 10
- Inverter, 11... - Microcomputer, 12... Transistor drive circuit, 13... Rectifier circuit.ゝ-7-

Claims (1)

[Claims] 1. An electric compressor is operated by an inverter consisting of an AC/DC conversion circuit that converts AC input from an AC power source into DC and smoothes it, and a DC/AC conversion circuit that further converts the DC into AC. In an air conditioner configured to operate, the detection circuit detects and outputs the DC output voltage of the AC/DC conversion circuit, the control means controls the output frequency of the DC/AC conversion circuit, and the output of the detection means and a set value, and a setting means for reducing the maximum frequency set by the control means to a predetermined value when the output of the detection means falls below the set value. Machine.