JPS60229670A - Overload protecting circuit - Google Patents

Abstract

PURPOSE:To detect a compressor operation by a commercial power source circuit and an overload at a compressor operating time by an inverter by one detector by mounting an overload detector between the compressor and a switching relay. CONSTITUTION:An overload detector 8 is mounted between a compressor 2 and a switching relay 7, and the output is input to a refrigerator controller 4. If the compressor 2 becomes an overload state at a compressor operation time by a commercial power source 1 and compressor operating time by a controller 4, a control signal is input to the controller 4 by the detector 8, a triac 3 is turned OFF or an inverter 5 is stopped.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention provides a refrigerator/freezer in which a compressor is operated in combination with a commercial power supply circuit or an inverter circuit, and in which one overload detection circuit is used to This is an overload protection circuit for refrigerators and freezers that can detect overloads during operation in the motor circuit.

[Background of the invention]

Conventional overload protection during compressor operation using a commercial power supply circuit and compressor operation using an inverter circuit each has an overload protection circuit, and there is no common line for transmitting signals between the refrigerator control circuit and the inverter circuit. Therefore, the signal was transmitted using a coupling element such as a photocoupler. In this case, two overload detection circuits are required, and the use of couplers and the like has the drawback of increasing costs.

[Purpose of the invention]

An object of the present invention is to use a single overload detection circuit to detect overloads during compressor operation by a commercial power supply circuit (commercial power supply circuit) and compressor operation by an inverter circuit, and to provide an inexpensive overload protection circuit. It is.

[Summary of the invention]

When operating a compressor using a commercial power supply circuit, it is necessary to detect overload to protect the compressor, and the same applies when operating using an inverter circuit. In this case, adding an overload protection circuit to each requires two detection circuits, and since there is no common line between the refrigerator control circuit (which outputs compressor on/off output) and the inverter circuit, a coupling element such as a photocoupler is required. Therefore, the circuit becomes complicated. Therefore, one overload detection circuit is used to detect overloads in each operation mode.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram of an embodiment of the present invention, where 1 is a commercial power source and 2 is a compressor. Reference numeral 3 denotes an AC control element (hereinafter referred to as a triac) which uses the commercial power source 1 to turn on and off the compressor 2, and these elements constitute a commercial power source circuit. 4 is a control circuit for the refrigerator, which outputs an output to turn on and off the compressor 2 depending on the internal temperature of the refrigerator, and also outputs an output to switch between compressor operation by a normal commercial power circuit and compressor operation by an inverter circuit. , and also processes the compressor overload signal and stops the compressor.

5 is an inverter circuit that rotates the compressor 2 in a certain frequency range. Reference numeral 6 denotes a current peak detector of the inverter circuit, which is provided to protect the inverter output elements. Reference numeral 7 denotes a relay circuit that allows the control unit 4 to switch between compressor operation using the open power supply circuit and compressor operation using the inverter circuit 5.

8 is an overload detection circuit inserted between the compressor 2 and the switching relay circuit.

Normally, the switching relay 7 is connected to the commercial power supply 1 and controls the operation of the compressor via the triac 3 based on the output signal of the refrigerator control circuit (hereinafter referred to as the control circuit) 4. In this case, when the compressor 2 falls into an overload state, the overload detector 8 detects the overload and inputs it to the control circuit 4. Therefore, the triac 3 of the compressor 2 is turned off by the control circuit 4, and the compressor 2 is stopped. Next, when it becomes necessary to operate the compressor 2 in a certain frequency range, the relay circuit 7 is switched to the inverter circuit 5 side based on the output signal of the control circuit 4. For this reason, the compressor 2 is operated in a certain frequency range. Even in this case, if the compressor 2 falls into an overload state, a compressor stop signal is input from the overload detector 8 to the control circuit 4, and the compressor 2 is stopped. FIG. 2 shows details of the overload detection circuit 8, where 9 is a current transformer for detecting overload of the compressor 2, 10 is a diode for rectifying the secondary output of the current transformer, and 11 is a resistor. 12 is a voltage comparator, and 13 is a DC voltage for arbitrarily setting an overload current (stopping the compressor). When the compressor 2 is overloaded, a current flows through the compressor 2 and a DC voltage 13 is applied to the secondary side of the current transformer 9.
A voltage larger than the voltage determined by is generated, the voltage comparator 12 is activated, and an overload signal is input to the control circuit 4, the compressor 2 is stopped, and the compressor 2 is protected.

〔Effect of the invention〕

As described above, the present invention provides overload protection for each operation mode with one overload detection circuit 8, eliminates the need for a separate overload protection circuit, and eliminates coupling elements associated with it, resulting in cost reduction. Furthermore, reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention in which one overload detection circuit is used to protect the compressor from overload in each operation mode, and FIG. 2 is a detailed diagram of the overload detection circuit. DESCRIPTION OF SYMBOLS 1... Commercial power supply, 2... Compressor, 3... AC control element (TRIAC), 4... Refrigerator control circuit, 5...
...Inverter circuit, 6...Current peak detector, 7.
・Relay for switching commercial power supply and inverter circuit, 8
... Overload detection circuit, 9... Current transformer, 10.
...Diode, 11...Resistor, 12...Voltage comparator, 13...DC voltage. Agent Patent Attorney Akio Takahashi

Claims (1)

[Claims] 1. It has a commercial power supply circuit that operates the compressor at the commercial power frequency, and an inverter circuit that operates the compressor in a certain frequency range regardless of the commercial power supply, and a signal from the refrigerator control circuit can be used to connect the commercial power supply circuit or the inverter circuit. In a refrigerator-freezer equipped with a switching relay, an overload detector is installed between the compressor and the switching relay, and the overload detector detects overload when the compressor is operated by the commercial power circuit and when the compressor is operated by the inverter circuit. An overload protection circuit for a refrigerator-freezer, which is characterized by detecting