JPH0151788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality detection device for a tank load circuit that detects an abnormality in a tank load circuit energized by a load commutation type inverter.

A load commutation type inverter supplies high frequency AC power to a tank load circuit, that is, a parallel resonant circuit consisting of a resistor, a capacitor, and an inductance. Examples of the load include an induction furnace, an induction heater, and the like.

Figure 1 shows a circuit illustrating a general load commutation type inverter, in which a commercial frequency AC power source 1 is connected to a rectifier 2.
The output of the rectifier 2 is smoothed by a smoothing reactor 3 connected between the rectifier 2 and the inverter 4, and a continuous DC current is supplied to the inverter 4. Furthermore, the inverter 4 converts this direct current into high frequency single-phase alternating current and supplies it to the above-mentioned parallel resonant circuit. The type of inverter in which power is continuously supplied to the inverter 4 by the smoothing reactor 3 and the capacitor 5 is connected in parallel with the load 6 as described above is called a load commutation type inverter.

It is generally known that load commutation type inverters cannot be operated unless the current phase leads the voltage phase as an operating principle.

Induction furnace, which is the load, the power factor of induction heating is 0.2 to 0.4
The power factor becomes a relatively lagging power factor, and in order to make this a leading power factor, a capacitor 5 of considerable capacity is connected, and even if one of the capacitors is punctured, the inverter will not be able to start. Therefore, it is necessary to spend a lot of time to find a defective capacitor among a large number of capacitors.

In addition, even if the load coil is shorted between layers, the inverter will not be able to start.Moreover, the load coil is molded with refractory material to protect it from heat, and it takes a lot of effort to discover abnormalities in the load coil. have to spend time.

In this way, load commutation type inverters cannot be started even if there is an abnormality in the load, and it is abnormal to determine whether the cause is on the power supply side, the load side, or the load side. This is an essential element for early detection.

In the past, when it became impossible to start, it was difficult to determine whether the cause was the power supply or the load, and a lot of time was spent finding the abnormality, which also affected production.

SUMMARY OF THE INVENTION An object of the present invention is to provide an abnormality detection device for a tank load circuit that quickly determines whether the cause is the power supply side or the load side when a load commutation type inverter becomes unable to start.

Hereinafter, the present invention will be explained with reference to the drawings. Second
The figure shows a configuration diagram as an embodiment of the present invention.

In FIG. 2, an energy storage circuit such as a capacitor 8 is charged in advance by a DC power source 7, a gate pulse of an inverter 4 is blocked, and a gate pulse is applied to a thyristor 9 connected to the capacitor 8. When energy is released, if the tank load circuit is normal, capacitor 8
The tank load circuit causes parallel resonance due to the energy from the tank, and the voltage waveform of the tank load circuit repeatedly oscillates as shown in FIG. On the other hand, when there is an abnormality such as a puncture of the capacitor in the load tank circuit or a short circuit between phases of the windings, even if the energy of the capacitor 8 is applied to the tank load circuit in the same way as above, the load voltage will oscillate as shown in Figure 3b. The waveform stops after a few cycles or stops oscillating altogether.

As mentioned above, focusing on the fact that there is a difference in the vibration waveform when there is an abnormality in the load tank circuit and when there is no abnormality, the frequency of the load voltage is counted by the counter 11, and if the number is less than a certain value, then If so, you can discover that there is an abnormality in the load tank circuit.

[Brief explanation of drawings]

Fig. 1 is a general circuit diagram of a load commutation type inverter, and Fig. 2 is a configuration diagram showing an embodiment of the present invention.
The figure is a voltage waveform diagram of the load circuit. 2... Rectifier, 3... Smoothing reactor, 4...
...Inverter, 5...Capacitor, 6...Load,
7...DC power supply, 8...Charging capacitor, 9...
...discharge thyristor, 10...instrument transformer, 1
1...Counter.

[Claims]

1. An output noise detection device connected to an electrical detector, a spectrum calculation device that calculates a power spectrum or a linear spectrum of noise based on the output of this detection device, and a spectrum calculation device that calculates a noise power spectrum or a linear spectrum based on the output of this detection device, and detects that high-order white noise is present in the output of this spectrum calculation device. a fitting device that performs an operation to match spectra when passing through a delaying element and obtains a higher-order delaying element passage characteristic of white noise; and an estimation device that estimates a response characteristic of the detector based on the output of the fitting device. A detector response characteristic estimating device comprising: