JPS58159624A - Inverter with impact preventing unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling device that drives a compressor via an inverter, and is intended to prevent destruction of the inverter, protect the compressor, or protect the compressor from damage when abnormal voltage is applied to the compressor for some reason. This invention relates to an inverter equipped with a shock prevention device that can prevent electric shock to the inverter.

In an electromagnetically driven compressor (compressor) driven by a DC power source via a DC/AC inverter, the method for electrically controlling the drive coil of the compressor is 1, for example, as described in Japanese Patent Application No. 49-40191 filed by the same applicant. It is disclosed in the book.

For example, the device shown in FIG. 1 is an example of a circuit that realizes such a control method, and its detailed operation can be found in the above-mentioned patent application issued in 1983.
Although it is clear from the specification of No. 40191, the outline thereof will be explained as follows. That is, in FIG. 1, an alternating current is generated from a DC power supply via an inverter INV to drive a compressor drive coil pw.
When rI turns on, the primary winding 11 of transformer T
If a current begins to flow in the direction of the solid line arrow in s, an electromotive force is generated in the first winding W3 in a direction that obstructs the direction of the current, and a current as shown in the dotted line arrow begins to flow. This causes the current to flow through the transistor Trot resistor R4 and the capacitor CM +
Current flows through diode D and transistor T
r l becomes more conductive, but the pace current of transistor Tr+ decreases as capacitor Cs is charged to the next level.

Resistor R4+ Determined by the time constant determined by the resistance values of other circuit elements. Then, the transistor T r l is I
c') bpH・IB (However, hpg is the current amplification factor, I
When the switch-off condition of (Bi, pace current) is satisfied, the transistor Trx transitions from the on state to the off state. Due to this rapid voltage drop between the collector and emitter of transistor Ty+, an electromotive force is generated that prevents the decreasing current, and an induced current begins to flow in the direction of the solid arrow in the first winding Wt. is the transistor Tde4. The current begins to flow through the capacitor Cat resistor R4+ and the diode Da, the transistor Tr is turned on and the transistor Tr1 is turned off, and the above operation is repeated.

The drive coil pw is energized by the energy converted from direct current to alternating current. In this case, since the time constant of IClR4 is set to a value corresponding to the vibration period of the compressor, the transistor Tdel
! :Trt is now turned on and off alternately.

The present invention is designed to protect the compressor or inverter when an abnormally high voltage is applied to the cooling device for some reason in the device shown in FIG. The purpose of the present invention is to provide a shock prevention device for a compressor inverter that protects the compressor inverter and prevents electrical shock to the human body if the output terminal of the inverter is touched in the above-mentioned no-load condition. .

For this reason, in the impact protection device according to the invention.

A feature of this system is that if an abnormally high voltage appears on the drive coil side of the compressor, it is detected and the shock prevention device shuts off both mutual on/off transistors for DC/AC conversion in the inverter. .

Next, embodiments according to the present invention will be described with reference to the accompanying drawings.

FIG. 2 shows one embodiment of the shock prevention device of the present invention.

In FIG. 2, the device includes a voltage detection section 100. Photo coupler 200. and a control unit 300, including input terminals 1.2.3.4. and 5.6 are connected to corresponding terminals 1-6 in FIG.

The voltage detection section 100 has diodes DIl to DI4.

A Zener diode ZD is placed in the center of each side of the diode.
and a resistor R1s are connected in series, and the light emitting diode side of the photocoupler 200 is connected to the series circuit. C1l is an electrolytic capacitor.

On the other hand, the control unit 300 has a diode D+i+DB・,
Transistor Tr*, timer TM composed of an IC chip, resistor R14, RB, RI constituting a time constant
It consists of SICtt+ and capacitor C1I. The operation of the circuit configured in this way will be explained next.

Now, let us consider a case where, for example, the secondary side of the transformer T of the inverter INV becomes unloaded, and the voltage on the secondary side of the transformer increases. Then.

In Fig. 71, the rising voltage between terminals 5 and 6 is applied via the terminals 5 and 6 of Fig. 2, for example, through diodes D, -R+t -C.
A rectified current flows as +t -D 14 and charges the electrolytic capacitor C1l, but when the voltage applied to Ic,1 exceeds the breakover voltage of the Zener diode ZD, a photo force is generated through the Zener diode ZD and the resistor R11, and the electrolytic capacitor C1l is charged. A current flows through 200 and the light emitting diode of the photocoupler PC 7 emits light, which turns on the phototransistor which is the light receiving element of the PC, thereby triggering the trigger 5 of the timer TM via the capacitor CI3.

Therefore, this causes the output terminal 3 to shift from the LOW state to the HIGH state, and the transistor Trs turns on. Therefore, the diode DIsD! Since a conduction current flows through the transistor Trg through the transistor Trg, both the transistors Tr1 and Try (Fig. 71) of the inverter INV are turned off, and their output drops to zero level. However, due to the previous conduction of the transistor T r H, the capacitor CI! , after the time constant of the time constant circuit consisting of the resistor R1m, the capacitor C11 has finished charging, so the output terminal 3 of the timer returns from HIGH to LOW.

Therefore, the transistor Tr6 changes from on to off, and the inverter circuit INV starts to start up again.

However, at this point, if an abnormal voltage different from the normal output still appears on the drive coil side of the secondary side of the transformer T, the above operation is repeated and the inverter circuit I
The output of NV is maintained at zero level, otherwise producing normal on/off output.

As described above, the device of the present invention prevents damage to the inverter when abnormal high voltage is applied to the cooling device, or when the inverter becomes unloaded due to disconnection on the compressor side, or in such cases. This prevents electric shock to the human body due to contact with other objects.

[Brief explanation of the drawing]

FIG. 1 shows an inverter circuit including a drive coil of a compressor to which the device of the present invention is applied, and its related devices. FIG. 2 each shows an embodiment of the impact protection device according to the invention. In the figure, (100) is a voltage detection section, (200) is a photocoupler, (300) is a control section, (ZD) is a Zener diode, (TM) is a timer, (Di = H + 11
) indicates a diode, (R 11 + 1m-) indicates a resistor, and (C 11 + 1m-) indicates a capacitor. Patent applicant: Sawafuji Electric Co., Ltd.

Claims (1)

[Scope of Claims] A time constant circuit having a time constant corresponding to the vibration period of the compressor, and a time constant circuit that is determined by a relationship between the time constant and a signal responsive to the vibration period and that alternately corresponds to the operation of the compressor. In an inverter for driving a compressor equipped with a switching device that turns on and off. A shock prevention device is provided to detect the output voltage of the inverter, and only when the voltage detected by the shock prevention device is larger than a predetermined value, the switching device is controlled to abruptly reduce the output voltage level to near zero level. An inverter equipped with an anti-equilibrium device that allows the inverter to fall.