JP2005057980A - Power control of electric motor and generator using magnetic energy regenerative current switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance an output by improving a force factor of a rotating machine all over the operating range including the number of revolutions. <P>SOLUTION: A snubber energy regenerative two-way current switch is connected in series between the rotating machine and a power supply or an electric motor and a load, and the switch is turned on or off by adjusting its phase to that of a flowing current. Thereby, a reactance voltage is compensated by accumulating magnetic energy in a capacitor and adding its voltage to the power supply voltage. As a result, the waveform of the flowing current is controlled and the force factor is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

In the present invention, when an electric motor is connected to a power source or a generator is connected to a load, a magnetic energy regenerative switch composed of a semiconductor device is connected in series, and is turned off in synchronization with the phase of the power supply voltage. In the case of a generator, the power factor of the motor current is improved or increased by the same effect as the series capacitor by supplying the power voltage by turning on in synchronization with the voltage phase and supplying it. The present invention relates to control for increasing output voltage.

Electric motors and generators perform energy conversion between electricity and machine through the interaction of magnetism and current. However, when the motor rotates at high speed, the frequency of the current increases, and reactance voltage is generated due to the presence of elements that delay current such as leakage inductance. As the current decreases, the rotating machine torque decreases, and eventually the output of the electric motor and the generator decreases.

In order to improve the power factor of a load having a conventional inductance, it is well known and partially implemented to cancel the reactance voltage by inserting a capacitor in series (for example, series capacitor compensation in a power transmission line).

However, since the capacitor capacity increases and instability may occur, it is not widely used.

There is a snubber energy regenerative bidirectional current switch that cuts off current at an arbitrary timing, accumulates magnetic energy at that time in a storage capacitor, and can be regenerated to a load at the next turn-on (see Patent Document 1).

If this switch is connected to a full-wave rectification configuration as shown in Fig. 1 and a snubber energy storage capacitor is connected to the DC generation terminal, this switch becomes a bidirectional lossless switch for the alternating current terminal. It is.
Patent Publication 2000-358359

  In electrical / mechanical energy conversion equipment such as electric motors and generators, the power factor in the high-frequency operating range is improved to increase the current, so that the reactance voltage by the conventional series capacitor method can be compensated. It was not adopted except in a special area because of its large size, large size, and the possibility of unexpected instabilities such as harmonic vibrations and electrical / mechanical coupling problems.

If the role of this series capacitor can be replaced with a small-sized, low-priced DC capacitor with the size of a semiconductor switch and capacitor, it becomes a power factor compensator that can control instability regardless of frequency, and increase the electromechanical conversion output of the rotating machine Can be made.

  A snubber energy regenerative bidirectional current switch (see Patent Document 1) that cuts off the current, accumulates the magnetic energy at that time in the snubber energy storage capacitor, and can be regenerated to the load the next time it is turned on or between the motor and the power source, or By connecting in series between the generator and the load, the magnetic energy of the current is stored in the capacitor in accordance with the timing of the voltage phase or the rotation phase, and when discharged, the same effect as the series capacitor is obtained.

  The function of the series capacitor for power factor improvement can be replaced with a DC switch with a small switch size and a capacitor size, and the on / off control synchronized with the voltage frequency can always maintain the current power factor at 1, and harmonic resonance, etc. Instability is unlikely to occur. (Independent of frequency, series capacitor action)

In the case of an electric motor, a reactance voltage is automatically generated by a magnetic energy regenerative switch and is connected in series with a power source, so that the power source voltage can be lowered accordingly. (Reducing power supply voltage)

When the motor or generator is operated in a high speed or high frequency region, the reactance voltage is automatically compensated by controlling the current power factor to 1 with this switch. There is an effect of increasing. (Torque increasing action at high speed)

Since the generator has the effect of increasing the output voltage, in the case of the same output, it can be said that the copper loss is reduced and the efficiency is increased as the current decreases. (Generator loss reduction action)

A bidirectional current switch that regenerates magnetic energy is connected in series between the rotating machine and the power supply or load, and is turned on / off by a voltage phase of the power supply or a phase signal that matches the position of the rotating machine. At this time, the capacity of the capacitor is first selected so that the magnetic energy of the rotating machine can be stored. However, if the capacity is increased, the voltage waveform changes, so it should be selected according to the requirements of the system. A small capacitor is used to suddenly change the current in a pulsed manner, and a large capacitor is preferred to change slowly.

  FIG. 1 shows an experimental circuit for demonstrating the principle of the present invention.

A 50 Hz 70V AC power supply 3 and a coil coil cooling fan motor 4 are connected via a magnetic energy regeneration switch.

The fan motor 4 has a rating of 100V50 Hz, a rating of 0.2 amperes, a self-inductance of 0.7 henry, and a DC resistance of 150 ohms.

Since the magnetic energy regenerative switch can use an optically coupled semiconductor relay in this embodiment, four of them are connected together with a reverse conducting diode as shown in FIG. 1, and the LED current for turning on and off the optically coupled semiconductor relay is as follows. This is done directly from the power supply voltage 3 with a current through a capacitor 0.47 microfarad. The energy storage capacitor 2 is a 200 V 47 microfarad electrolytic capacitor.

By turning on the switch 1 and the switch 4 at a phase advanced by 90 degrees of the power supply voltage by the switch on / off signal 9 of FIG. 2, the voltage of the storage capacitor 2 is added to the AC power supply voltage as shown in FIG. The coil current rises rapidly. If the two switches are turned off and the opposite switch gate G2 and switch gate G3 are turned on when the phase advances by about 180 degrees, the coil current rapidly increases because the voltage of the storage capacitor 2 is added to minus. To descend.

Thus, as a result of adding the capacitor voltage by advancing the phase by 90 degrees to the power supply voltage, the amplitude of the coil current increases. At this time, since the voltage of the storage capacitor is supplied because it regenerates the magnetic energy of the coil current, it does not need to be supplemented, and the capacitor voltage rises until the coil current reaches a power factor of 1.

Although the current waveform looks like a triangular wave, it is because the capacitance of the storage capacitor is increased.

As a result of the increase in current, the rotation speed of the fan 4 increases and reaches the rotation speed without a switch rated at 100 V at a power supply voltage of 70 V. That is, the magnetic energy regenerative switch generates a voltage of 30 V. The voltage is generated by regenerating the magnetic energy of the load.

Since the power factor of the electric motor can be improved with a magnetic energy regenerative switch, the same current can flow even if the power supply voltage is lowered. In particular, in the case of a DC brushless motor, a large output can be output in a high speed range.

In the case of a generator, if this switch is connected in series to improve the power factor of the current, a high voltage can be output by compensating for the voltage drop of the leakage reactance of the generator. When the output of the generator changes with the wind or the frequency changes like wind power generation, the series capacitor does not satisfy the resonance condition and becomes overcompensated, but if this switch is used, it will be automatically The power factor is compensated, and the loss decreases as the generator output voltage increases.

A magnetic energy regenerative switch is connected in series to a torsion coil type induction motor / fan, and the power factor of the current is improved by switching the switch with a synchronized signal, indicating that the rotation speed is equivalent to 100V at a voltage of 70V. Model experiment circuit diagram The figure explaining the power supply voltage of the circuit of FIG. 1, a current waveform, etc.

Explanation of symbols

1 optical coupling semiconductor relay switch (control LED current 3mA, DC current 1.3A-200V)
2 energy storage capacitor (47 microfarad, 200V)
3 power supplies (70V)
4 winding coil type induction motor (50Hz 100V 0.2A, 0.7H, 150 ohm)
5-phase signal generator (0.47 microfarad and diode)
6 Power supply voltage waveform 7 Motor voltage waveform 8 Current waveform 9 Switch on / off signal

Claims (1)

A snubber energy regenerative bidirectional current switch is connected in series between the AC rotating machine and the power supply or the load in the case of a generator, and the switch is turned on / off according to the voltage phase of the power supply or the rotating phase of the rotating machine. By turning on and off the rotating machine current once or multiple times in a half cycle, the magnetic energy of the current is stored in the energy storage coil, and the reactance voltage of the rotating machine is compensated in series with that voltage. An electric power control device characterized by changing a current waveform and a power factor.

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