JPS59175336A - Protecting circuit at nongrounding time of electrostatic paying dc high voltage power source - 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 is a DC high voltage power supply device for electrostatic painting! (hereinafter referred to as a power supply device) relates to a protection circuit when the device is not grounded.

In the conventional power supply devices, the installed type is widespread9, and reliable grounding is ensured, and there are very few failures of the power supply device due to forgetting to connect the ground.

However, with recent advances in technology, power supplies have become smaller and lighter, and products have been developed that can be hung on the shoulder or waist.

Such a portable power supply device has the disadvantage that the stain source device may malfunction due to forgetting to ground the device or disconnection of the grounding wire during movement.

FIG. 1 shows a basic circuit of a specific example of a conventional power supply device.

In the figure, P is a one-end grounded power supply, T is a one-end grounded transformer, S is a rectifier, C is a capacitor, K is a high-voltage coaxial cable, R is a resistor, G is a painting gun, and A is an object to be painted ( metal), E is the ground terminal, Y is the transformer T1 rectifier S,
This is a case that houses a capacitor C.

Now, as an example, assume that a power supply P is supplied with filoOVAc, the voltage is stepped up to 50kVAC by a transformer T, DC is exchanged by a rectifier S, and this DC potential is smoothed by a capacitor C to generate a DC output voltage of 70kVDC. do. This output normal pressure is applied to the painting gun G through one resistor R to the coaxial cable.
A corona current 11 is caused to flow toward the object A to be coated. The load characteristics at the tip of the painting gun G at this time are
As shown in the figure. This characteristic is 70 kVD at no-load generated voltage.
At C, when the painting gun G comes into contact with the object A to be painted,
The resistor 8iSR is selected so that the voltage is zero and the current value at this time is 150 μA.

In the case where the grounding terminal E is open in Fig. 1, when the power supply P is turned on, the grounding terminal E, which should be at ground potential, floats to 70kVDC''!, so the secondary side of the transformer T There was a drawback that flash faults occurred between the line and case Y or between the supply power line.

The present invention aims to provide a protection circuit for a power supply device when the power supply device is not grounded, which eliminates the above-mentioned drawbacks.

The basic circuit of one embodiment of the present invention shown in FIG. 3 will be explained below.

Generally, the power supply is grounded at one end based on electrical equipment technical standards, and this one end ground potential is used to form a closed loop with a high voltage potential.

In FIG. 3, the same parts as in FIG. 1 are given the same reference numerals.

A nonlinear element Z for this purpose is inserted between the grounding terminal E of the DC secondary side of the power supply device and the U or V phase of the primary side supply power line.

As shown in FIG. 4, this nonlinear element Z generally exhibits a high impedance for small current values, and shifts to a low impedance as the current increases.

In other words, the limiting voltage hardly changes as the current increases. The present invention takes advantage of this property. In one example, the nonlinear element is
Select a product that has a discharge starting voltage of 5 MΩ or more at V and is higher than the supply voltage in the AC test.

In the case where the ground terminal E is open in Figure 3, when the power supply is turned on, the current loop is as shown by the dotted line: transformer T- + rectifier S → pressure coaxial cable → resistor R →
A closed loop is formed: painting gun G- + object A to be painted → one end of the power supply U or V phase grounded side → nonlinear element Z → transformer T. Here, the floating potential X of the grounding terminal E is: (1) When the supply power V phase is grounded, X- (output current 12vX impedance of the nonlinear element)
This maximum voltage does not exceed the limit voltage of the nonlinear element. (2) When the supply power supply U phase is grounded, it is expressed as: X = (supply power supply voltage + (output current 1zu Do not exceed (voltage).

By the way, when using a product whose limiting voltage of nonlinear element Z is 300V, the above DC generation voltage is 70kVD.
When C, the maximum floating potential of the ground terminal E is as shown in the formula (2).
00V) Medium 141+300V±441■ Tonashi, 441V for the floating potential of 70kV in Figure 1
reduced to Further, if the ground terminal E at this time has a withstand voltage exceeding 441V with respect to the ground potential, this power supply device can operate normally.

Although the above embodiment has been described using a non-linear element, an arrester having a firing voltage higher than the supply voltage may be used in place of the non-linear element.

As mentioned above, the present invention allows the power supply to operate normally even in the case of forgetting grounding or disconnection in DC high-pressure snow mud for electrostatic painting, and is useful as a safety circuit, making it useful for industrial and industrial purposes. It is of great spiritual value.

[Brief explanation of the drawing]

Figure 1 is a basic circuit diagram of a conventional high-voltage DC power supply for electrostatic painting, Figure 2 is a load characteristic diagram of output voltage versus output current of a specific example of a conventional high-voltage DC power supply for electrostatic painting, and Figure 3 4 is a basic circuit diagram of an embodiment of a DC high-voltage power supply device for electrostatic coating incorporating a protection circuit when not grounded according to the present invention, and FIG. 4 is a diagram showing the limited voltage versus current characteristic of a nonlinear element. P: Supply power T, one end grounded transformer S: Rectifier C: To the capacitor: High voltage coaxial cable R: Resistor G: Paint gun A: Non-painted object E: Ground terminal 2: Nonlinear element Patent applicant Nippon Capacitor Industry Co., Ltd. Company procedure amendment (
spontaneous) 1. Display of the incident 1982 Patent Application No. 49293 Bow 2 Name of the invention Protection circuit for non-grounding of DC high voltage power supply device for electrostatic painting 3
Relationship with the case of the person making the amendment Patent applicant 4, the subject of the amendment is the ``title column of the invention in the specification,'' ``the scope of claims in the specification,'' and the ``detailed description of the invention column in the specification.'' 5. Contents of the amendment (1) The title of the invention on page 1 of the specification is corrected as follows. "Protection circuit for ungrounded DC high-voltage power supply for electrostatic painting" (2. The claims are amended as follows. [In the DC high-voltage power supply for electrostatic painting, one end of the supply power is grounded, DC secondary side grounding terminal E of DC high voltage power supply
A discharge start type that is higher than the supply voltage between the supply voltage AC line U or V phase and the supply voltage AC line. This is a protection circuit for a DC high-voltage power supply for electrostatic painting when a voltage arrester or non-linear element Z is inserted to suppress the floating potential when the voltage is not grounded. (3) Specification page 2, No. 16
Correct "DC exchange" in the line to "DC degree conversion".

Claims (1)

[Claims] In a DC high-voltage power supply for electrostatic painting, the supply power is grounded at one end, and a discharge that is higher than the supply power voltage starts between the DC secondary side grounding terminal E of the DC high-voltage power supply and the supply power AC line U or 7 sets. A protection circuit for a DC high-voltage power supply device for electrostatic painting when a voltage arrester or non-linear element 2 is inserted to suppress floating potential when not grounded.