JPH09245988A - Secondary voltage fluctuation adjusting circuit of static eliminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the costs and provide controllability for a secondary voltage fluctuation within the allowable range even at the time of using with any desired length in the longest range of a high voltage cable by inserting a voltage compensation resistance having an appropriate value previously in the primary side of a transformer. SOLUTION: When the primary current increases and a secondary voltage is generated with increasing inter-wire capacitance of a high voltage cable, a voltage drop caused by a voltage compensation resistance 10 inserted in the primary winding cancels the rise of the secondary voltage, which causes a reduction of the secondary voltage fluctuation. If the resistance value is represented by Ra and the winding ratio of transformer 3 by (a), the equivalent resistance value viewed from the secondary side becomes a<2> Ra, and it is possible to determine Ra from the equivalent circuitry. Ra can be decided so that |V2 |=|aV1 | under the condition C=Cmax, where the change in the inter-wire capacitance Cc of the high voltage cable 4 ranges from zero to Cmax. The actual measurements of the peak of the error in the secondary voltage V2 ranged from -0.5% thru +2.5%, while corresponding calculations range from zero to +2.1%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary voltage fluctuation adjustment circuit caused by fluctuations in the line capacitance of the secondary side cable of a static eliminator for neutralizing statically charged objects.

[0002]

2. Description of the Related Art Since semiconductor devices are easily destroyed by static electricity, it is necessary to remove static electricity during storage and manufacturing processes. Therefore, conventionally, the static eliminator having the configuration shown in FIG. 4 has been used in the semiconductor device manufacturing process and the like.

FIG. 4 is a circuit diagram showing the structure of a conventional static eliminator. In FIG. 4, 1 is a commercial AC power supply (voltage value 1
00 [V]), 2 is a power switch connected in series to the commercial AC power supply 1. 3 is a step-up transformer, 1
A commercial AC power supply 1 and a power switch 2 are connected to the next side. Reference numeral 4 is a high-voltage cable connected to one end of the transformer 3 on the secondary side. Reference numeral 5 is a static elimination electrode composed of a ground electrode 6 and a discharge electrode 7. The discharge electrode 7 is connected to one end of the secondary coil of the step-up transformer 3 via the conductor portion of the high voltage cable 4. The ground electrode 6 is connected to the other end of the secondary coil of the step-up transformer 3 via the ground wire of the high-voltage cable 4 and grounded. Further, 8 is a charged object such as a semiconductor device which is opposed to the static elimination electrode 5 in a non-contact state.

In the above structure, when the power switch 2 is in the ON state, the output voltage V ₁ of the commercial AC power supply ₁ is boosted by the boosting transformer 3 and the secondary voltage V ₂ of positive or negative (for example, to the discharge electrode 7) (for example, , Its value is 7 [kV]) is applied alternately. Then, corona discharge occurs between the discharge electrode 7 and the ground electrode 6, and the air around the static elimination electrode 5 is alternately ionized into positive and negative ions. As a result, ions of either polarity are attracted to the charged object 8 and recombined with the charged charge of the charged object 8 depending on the polarity of the charged charge of the charged object 8, and as a result, the charged charge is neutralized. .

[0005]

By the way, in order to avoid the risk of electric shock to the human body due to leakage of the secondary voltage V ₂ from the static eliminator, a coaxial cable may be used as the high voltage cable 4 in FIG. is there. In such a case, the load on the secondary side of the step-up transformer 3 becomes capacitive. Reference numeral 9 indicates the line capacity of the high voltage cable 4.

FIG. 5 is a circuit diagram showing an electrical equivalent circuit in the configuration of FIG. 4, and includes an equivalent series resistance R _t of the step-up transformer 3, a leakage inductance L _t , and a line capacitance 9 (capacitance C of the high voltage cable 4). It is represented by a series circuit consisting of _c ). Further, aV ₁ is a voltage on the primary side of the step-up transformer 3 as viewed from the secondary side. Here, a is the winding ratio of the step-up transformer 3.

In the above structure, since the secondary voltage V ₂ of the step-up transformer 3 is determined by the voltage division of the secondary impedance including the leakage inductance L _t and the line capacitance 9, the high voltage cable 4 is extended and the line capacitance is increased. When 9 is increased, the leakage inductance L _t is apparently canceled by the capacitance, so that the divided voltage, that is, the secondary voltage V ₂ is rapidly increased. The practical allowable fluctuation range of the secondary voltage V ₂ is within ± 3%, but when the cable length is about 50 meters and the line capacity 9 is about 8,000 [pF], the increase is 10% or more. Impractical. Therefore, the step-up transformer must be designed and manufactured in accordance with the cable length, and there is a problem in that the cost is high.

The present invention has been made in view of the above circumstances, and by adding a simple additional element, it is possible to maintain the fluctuation of the secondary side voltage within a practical allowable range even when the high voltage cable is extended. It is also an object of the present invention to provide a static eliminator that can use a general-purpose step-up transformer and can reduce costs.

[0009]

In order to solve the above problems, the present invention provides a step-up transformer whose primary side is connected to an AC power source, and a discharge electrode connected to one end of the step-up transformer on the secondary side. An ion balance adjusting circuit for a static eliminator, the ion balance adjusting circuit being arranged so as to face the discharge electrode and having a ground electrode connected to the other end of the secondary side of the step-up transformer, It is characterized in that it comprises a voltage compensating resistance means interposed between the AC power source and the AC power source.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Action When the primary current increases and the secondary voltage rises due to the increase in the line capacity of the high-voltage cable, the voltage drop due to the voltage compensation resistance means inserted in the primary winding causes the secondary voltage to rise. And the secondary voltage fluctuation is reduced. (2) Embodiment Hereinafter, a secondary voltage fluctuation adjusting circuit for a static eliminator according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an electric circuit diagram showing a configuration of an electric circuit of a static eliminator having a secondary voltage adjusting circuit according to an embodiment of the present invention. The same parts as those in FIG. Omit it. In FIG. 1, reference numeral 10 is _a voltage compensating resistance means having _a resistance value R _a , which is inserted and connected in series with the primary side circuit of the transformer 3. Further, in the figure, reference numeral 12 is a static elimination electrode similar to the static elimination electrode 5 in FIG. 4, and reference numerals 14 and 15 are discharge electrodes and ground electrodes similar to the discharge electrode 7 and the ground electrode 6 in FIG. 4, respectively.

FIG. 2 is an equivalent circuit of the circuit shown in FIG. 1, and is different from the conventional equivalent circuit shown in FIG. 5 in that the voltage compensation resistance means 10 is additionally inserted in series. .
Resistance value of the voltage compensating resistance means 10 is R _a, the equivalent resistance seen from the secondary side if the winding ratio of the step-up transformer 3 is a, the a ² R _a.

[0012] The change in the capacitance C _c of the line capacitance 9 of the high-voltage cable 4 When 0 to C _max, when the capacitance C _c = C _max |
Optimally, the resistance value R _a is determined so that V ₂ | = | aV ₁ |. Hereinafter, the equivalent circuit is used for the calculation. The overall impedance Z is expressed by the following equation. _{^{Z = a 2 R a + R}} t + jωL t -j / (ωC max) i 2 = aV 1 / Z, V 2 = -i 2 j / (ωC max) However, in the above equation, j denotes an imaginary unit. From these relationships, | V ₂ | = | aV ₁ |

[0013]

[Equation 1]

This is the case. For example, regarding the step-up transformer 3, the number of turns a is 72, the value of the equivalent series resistance R _t is 14.3 [kΩ], and the value of the leakage inductance L _t is 99.
[H] and the frequency of the commercial AC power supply is 50 [Hz], the capacity C _max is 8250 [pF] (the capacity per unit length is 150 [pF / m], and the length is 55).
[M]), the resistance value R of the voltage compensation resistance means 10
the optimum value of _a becomes 26.5 [Ω]. FIG. 3 is a characteristic diagram showing the change of the secondary voltage V ₂ with respect to the change of the line capacity 9 of the high voltage cable 4, in which the dotted curve F shows the calculated value and the solid curve F ′ shows the measured value. The peak of the error of the secondary voltage V ₂ is 0 to + 2.1% in the calculated value, but is −0.5 to + 2.5% in the measured value.

In FIG. 3, a dotted curve G is a calculated value when the resistance value R _a is 29.5 [Ω], which is slightly larger than the calculated optimum value 26.5 [Ω], and G ′ is the calculated value. It is a measured value curve. The peak of the error in this case is −
1.9 to + 1.7%, but measured value is -0.6 to +
It is 1.9%, which is excellent as an error characteristic. That is, it is effective to adopt a resistance value slightly larger than the ideal calculated value. In any case, the voltage fluctuation is within ± 3%, and it can be sufficiently put to practical use.

Further, the dotted curve H in FIG. 3 is a calculated value in the case of the conventional configuration in which the voltage compensating resistance means 10 is not provided, and the error of the secondary voltage V ₂ is 8.4% at maximum. In this case, the actually measured value greatly exceeds the calculated value as shown by the solid curve H ', and a dangerous voltage rise occurs. Therefore, the extension of the cable is limited to be extremely short. The table below shows a summary of fluctuation errors in the above calculated and measured values.

[0017]

[Table 1]

[0018]

As described above, according to the present invention,
By inserting voltage compensation resistance means of an appropriate value in the primary side of the transformer in advance, the secondary voltage fluctuation can be controlled within the allowable fluctuation range even if the high voltage cable is used in an arbitrary length in the maximum length range. Therefore, it is not necessary to design and manufacture a transformer according to the cable length, and it is possible to contribute to cost reduction by sharing parts.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a configuration of an electric circuit of a static eliminator having a secondary voltage adjusting circuit according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit of the circuit shown in FIG.

FIG. 3 shows a change in the line capacity 9 of the high-voltage cable 4 with respect to 2
It is a characteristic diagram showing the change of the next voltage V _2.

FIG. 4 is a circuit configuration diagram showing a configuration of a conventional static eliminator.

5 is a circuit diagram showing an electrically equivalent circuit in the configuration of FIG.

[Explanation of symbols]

 1 Commercial AC power supply 3 Step-up transformer 4 High-voltage cable 6 Ground electrode 7 Discharge electrode 10 Voltage compensation resistance means

Claims (1)

[Claims] 1. A step-up transformer having a primary side connected to an AC power source, a discharge electrode coupled to one end of a secondary side of the step-up transformer, a discharge electrode arranged to face the discharge electrode, and the step-up transformer. An ion balance adjusting circuit for a static eliminator having a ground electrode connected to the other end of the secondary side of the step-up transformer, the voltage-compensating resistance means interposed between the primary side of the step-up transformer and the AC power supply. A secondary voltage fluctuation adjusting circuit for a static eliminator, characterized by: