JPS62123968A - Suppression of electrical noise in variable voltage variable frequency inverter - Google Patents

Abstract

PURPOSE:To contrive to absorb the current in a simple constitution which causes electric noise by providing for the zero-phase filter composed of a condenser grounding three-phase input wiring separately and a zero-phase reactor provided so as to put together the input wiring. CONSTITUTION:In a three-phase input wiring 7 of a variable voltage variable frequency inverter unit 4 the wiring of every phase is grounded separately through a condenser 3. The leakage current from a three-phase output wiring 8 and an induction motor 5 is almost absorbed through the condenser 3. In this case, as the condenser 3 grounding the three-phase input wiring 7 also absorbs the zero-phase current, the source of which is other equipment connected to the same three-phase power source, the absorption of the zero-phase current from other power sources is prevented by providing a zero-phase reactor 2 so as to put together the three-phase input wiring 7 on the way from a three- phase power source 1 to the inverter unit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention is directed to suppressing electrical noise caused by a potential difference that changes rapidly in steps between the output wiring of a variable voltage variable frequency inverter device and the ground. , regarding control methods. It is desired that this type of suppression method be as simple and effective as possible.

(Prior art and intervening points) With the Otani FJT switching element and the advancement of element application technology, inverter devices, especially sturdy and inexpensive induction 1 and UF variable voltage that can efficiently and steplessly control the speed of the motor, have been developed. Frequency (VVVP) inverter devices have become rapidly popular over the past few years.

However, in this type of v v' V F inverter device, high-speed switching, that is, high-speed sine wave pulse width modulation control is performed in order to reduce its own loss and make the output waveform a sine wave. Since the potential difference between the output wiring and the ground changes at high speed and generates various types of high frequency 111 noise, this type of noise becomes a problem when using the inverter device a.

Generally, the charging/discharging current I for the stray d, v capacitance that exists between the output wiring of a VVVF' inverter device and the ground, or between the windings of an induction motor as a load and a grounded frame. = aoπ is a considerable value because the step change period v (i) of the potential difference between the output wiring and the ground is extremely large, and most of it becomes a zero-sequence current. Therefore, equipment such as instrumentation equipment that is more susceptible to this type of 11°C atmospheric noise than general industrial equipment requires appropriate noise countermeasures.

As a measure on the inverter side to reduce the adverse effects of this type of electrical noise, the output wiring of the inverter device is grounded as metal tube wiring, and the inverter device itself, the induction motor, the metal tubes, etc. are grounded. While measures are being taken to reduce the impedance of wires to high frequencies, measures are being taken to improve the noise tolerance of the devices that receive the noise, or to change the wiring routes leading to the devices. Measures have been taken.

However, in order to obtain satisfactory results with these measures, there is a drawback in that both the parties generating the noise and those affected by it must purchase measures that are cumbersome and impose a heavy economic burden. I'm coming.

(Object of the Invention) In view of the above-mentioned drawbacks of various countermeasures against electrical noise generated by the output wiring of the variable voltage variable frequency inverter device, it is possible to eliminate the noise generation source such as the output wiring of the VVVP inverter device by simple measures. The purpose is to proactively absorb the current that causes electrical noise and reduce the impact on other equipment.

(Summary of the Invention) In order to achieve the above-mentioned object, the present invention provides the electrical noise suppression method described above, which includes a suitable capacitor for individually grounding three-phase input wiring on the input side of the inverter device, and the input wiring. By providing a zero-phase filter consisting of an appropriate zero-phase reactor provided so as to collectively
It absorbs the zero-phase current leaking to the ground from the output wiring of the inverter device, the induction motor as a load, etc., and suppresses the return of the current to the three-phase power supply side as much as possible.

(Embodiments of the Invention) Next, the present invention will be described in detail based on embodiments shown in the drawings.

In FIG. 1, a variable voltage variable frequency (vvVy) inverter device 4 receives three-phase AC power from a three-phase AC power source 1 via a three-phase input wiring 7, and connects the load (in this case, an induction motor) via its output wiring 8. Three-phase alternating current power of variable voltage and variable frequency is supplied to the motor 5, so that the 'R motor speed control is performed steplessly. Furthermore, in the case of the vvvp inverter device 4 shown in FIG. are grounded via individually connected capacitors 3.

In that case, as already mentioned, in this type of inverter device 4, high-speed sine wave pulse width modulation control is generally performed using transistors.
The 11-to-2 position difference between each phase output wiring 8 and the ground V changes stepwise at high speed, and its value π becomes extremely large. Charging fit! v Ryuko. =Co7i- is generated. Historically, a similar current occurs in the induction motor 5 connected to the output end of the output wiring in the stray capacitance between its winding and the grounded frame. (not shown). Since most of these currents are zero-sequence currents, they normally become leakage currents and flow through the ground.
If the neutral point of the transformer of the three-phase AC power supply 1 is grounded, it returns via the grounding wire and causes electrical noise to other devices connected to the power supply 1.

However, in the three-phase input wiring 7 of the variable voltage variable frequency inverter device 4 according to the present invention, each phase wiring is individually grounded via the capacitor 3. Most of the leakage 11f flow is collected through the capacitor 3 and is converted into a three-phase 'rti
Feedback to the source 1 side is significantly suppressed, and the influence of electrical noise on other devices connected to the three-phase power source 1 is reduced to such an extent that it hardly becomes a problem.

In this case, the capacitor 3 that grounds the three-phase input wiring 7 will also absorb the zero-phase current that is powered by other devices connected to the same three-phase power supply 1. A zero-phase reactor 2 is provided in the middle of the input wiring 7 leading to the inverter device 4 so as to bundle three phases at once to prevent absorption of zero-phase current from other power sources.

(Effects of the Invention) As described above, the present invention provides a method for suppressing electrical noise caused by a potential difference that makes a rapid step change between the output wiring of a variable voltage variable frequency inverter device and the ground. By providing a zero-phase filter on the input side of the inverter device consisting of appropriate capacitors that ground the three-phase input wires individually and a zero-phase reactor provided so as to bundle the input wires together, the output of the inverter device By absorbing the zero-phase current that leaks to the ground from wiring and induction motors as loads, and suppressing the current that returns to the three-phase power supply, the influence of electrical noise based on the current on other equipment can be reduced to almost no problem. Since the electrical noise can be reduced to such an extent that it does not cause electrical noise, there is an effect that no special defense measures are required for equipment receiving the electrical noise.

[Brief explanation of drawings]

FIG. 1 shows a schematic wiring diagram of a variable voltage variable frequency inverter device related to the electrical noise suppression method of the present invention. l Zero-phase reactor, 3: Grounding capacitor, 4: Variable voltage variable frequency inverter device, 7: Input wiring, 8: Output wiring.

Claims (1)

[Claims] 1) In a method for suppressing electrical noise caused by a potential difference that changes rapidly between the output wiring of a variable voltage variable frequency inverter and the ground, three-phase input wiring is individually connected to the input side of the inverter. A method for suppressing electrical noise in a variable voltage variable frequency inverter device, comprising: providing a zero-phase filter consisting of a suitable capacitor grounded to the ground and a zero-phase reactor provided so as to bundle the input wiring .