JPH043456Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an electromagnetic device used in an electromagnetic contactor, etc. In this type of electromagnet device, it is desired to reduce power consumption.

[Prior art]

A conventional device of this kind is shown in FIG. In Fig. 3, 1 is a power source, 2 is an operating coil for attracting the iron core, 3 is a transistor as a switching means, 4 is a flywheel diode, and the output 5 is a control circuit. The collector-emitter path is connected in series with the power supply 1, the flywheel diode 4 is connected in parallel with the operating coil 2, and the output 5 of the control circuit is connected to the base of the transistor 3. Although the power source 1 is shown as a DC power source for ease of explanation, it is generally used as a full-wave rectified single-phase AC power source.

As shown in FIG. 4, the control circuit 5 applies continuous pulses to the base of the transistor 3 for a predetermined time t necessary for inserting the iron core, and after the elapse of the predetermined time t, intermittent pulses are applied to the base. Therefore, a continuous current flows through the operating coil 2 when the core is inserted, creating a large attraction force, and after the core is attracted, an intermittent pulsed current flows to maintain the attraction state of the core.

[Problem that the invention attempts to solve]

When switching is performed by the transistor 3 in order to reduce the power consumption of the electromagnet device, noise intrudes into the power supply 1 due to the stray capacitance shown by the dotted line due to the change in potential at point a shown in FIG. If this noise is in the AM frequency band of the radio, it will enter the radio and have an adverse effect. For this reason, it is conceivable to connect the noise filter 7 as shown in FIG. 5, but unless the earth terminal A of the noise filter 7 is grounded, it will not be effective as a noise filter. Earth terminal A
In order to ground the noise filter 7, a capacitor with a withstand voltage of several kV is required, which has the disadvantage of increasing the size. Furthermore, it may be difficult to ground some electrical appliances using such electromagnetic devices.

Therefore, an object of the present invention is to eliminate the drawbacks of the conventional devices described above, and to provide an electromagnetic device that is non-grounded and can reliably remove noise in the AM frequency band.

[Means to solve the problem]

In order to solve the above-mentioned problems, this invention includes an operating coil for attracting the iron core, a switching means connected in series between the operating coil and the power source, and a device that continuously energizes the switching means when the iron is turned on and when holding the iron core. In an electromagnet device equipped with a control circuit for attracting and holding an iron core through intermittent energization, an LC parallel resonant circuit is connected between the power source, an operating coil connected in series, and switching means.

[Effect]

By connecting an L-C parallel resonant circuit between the power supply, the operating coil connected in series, and the switching means, a specific frequency band, in this case,
The impedance of the LC resonance circuit becomes infinite with respect to noise in the AM frequency band, and noise can be reduced.

〔Example〕

FIG. 1 shows an embodiment of the present invention, and the same components in FIG. 1 as those in the conventional device shown in FIG. 3 are given the same reference numerals, and their explanations will be omitted.

1 differs from FIG. 3 in that an LC parallel resonant circuit 6 is connected between a power supply 1, an operating coil 2 connected in series, and a transistor 3 serving as a switching means. In the LC parallel resonant circuit 6, the inductance value of L and the capacitance value of C are determined based on the parallel resonance frequency (c) based on the formula c=1/2π√LC. This value is selected to be set for AM frequencies with a narrow frequency range. In terms of the parallel resonance frequency (c) of this L-C parallel resonant circuit 6, its impedance is ideally infinite, and the L-C parallel resonant circuit 6 is responsible for the AM frequency band among the noise generated by the switching of the transistor 3. It is possible to reduce noise from entering the power supply 1.

Figure 2 shows actual noise measurement data when using the L-C parallel resonant circuit 6 according to the present invention (dotted chain line) and when using the conventional device (solid line), where the horizontal axis represents one frequency and the vertical axis represents one frequency. It is a decibel that is the logarithm of the power ratio. As is clear from this graph, the AM frequency band (455KHz~455KHz) is
1.6MHz), the noise is reduced.

In addition, in the above embodiment, a case was explained in which one LC parallel resonant circuit was used to remove noise in a specific AM frequency band, but it is also possible to provide a plurality of LC parallel resonant circuits having different resonant frequencies. Accordingly, noise caused by switching of the transistor 3 can be further reduced.

〔effect〕

According to the present invention explained above, by providing an L-C parallel resonant circuit, it is possible to reduce noise without grounding, and to compare the L-C constant with respect to the frequency of the noise to be reduced. can be easily determined. Further, since the capacitor C is not grounded, it has the advantage that a withstand voltage lower than the power supply voltage used is sufficient.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention;
3 is a circuit diagram showing a conventional device, FIG. 4 is a timing chart, and FIG. 5 is a circuit diagram showing another conventional device. 1...Power source, 2...Operation coil, 3...Transistor, 5...Control circuit, 6...L-C parallel resonant circuit.

Claims (1)

[Scope of utility model registration request] An operating coil for attracting the iron core, a switching means connected in series between the operating coil and a power source, and a control device that attracts and holds the iron core by continuously energizing the switching means when turning on the iron core and intermittently energizing it when holding the iron core. 1. An electromagnet device comprising a circuit, characterized in that an LC parallel resonant circuit is connected between the power source, an operating coil connected in series, and switching means.