JPS6010516B2 - AC motor drive device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a drive device for an AC motor, and particularly to a drive device suitable for a relatively small capacity AC motor such as a pulse motor.

The power supplied by general AC motors, pulse motors, etc. always contains an alternating current component, and the existence of that alternating current component contributes to the generation of driving torque (or propulsive force) in a predetermined direction. Frequency is responsible for rotational speed (or propulsion speed). In many special AC motors such as pulse motors, the current supplied to each winding is a DC pulse current in a fixed direction, but in this case as well, the supplied current is divided into DC and AC components. Then, there are those that generate a driving torque proportional to the product of the alternating current component and the direct current component, and those that generate a driving torque that is proportional only to the alternating current component.

An example of the former is found in reluctance motors, and an example of the latter is found in motors using permanent magnets. In any case, the existence of an alternating current component is a necessary condition, and the frequency of the alternating current component determines the speed of the motor. Therefore, "here, motors without a commutator (mechanical frequency conversion mechanism or inverter) are collectively referred to as AC motors. Figure 1 is a circuit diagram showing the configuration of a drive device for a secondary AC motor. An AC motor winding 2 and a semiconductor switch 3 are connected in series from a DC power source 1 through a current limiting resistor or a time constant improving resistor 5 at low speeds, and the semiconductor switch 3 is controlled to open and close by a conduction control command device 10. It controlled the power supply current to line 2.

Then, the diode 4 and the voltage suppressing means 100 or 10
0' is provided to suppress the transient voltage generated by the inductance of the winding 2 when the semiconductor switch 3 changes from conduction to non-conduction, and to suppress the voltage applied to the semiconductor switch 3 and the rate at which the current decreases. I was trying to make it a value.

This voltage suppressing means 100 or 100' is composed of, for example, a resistor or a parallel body of a resistor and a capacitor.

However, the stored energy (power) due to the inductance of the winding 2 increases as the frequency (high speed) increases.
The ratio to the motor output sometimes reached several tens of percent.

Furthermore, in pulse motors and the like, the output may be greater than the electric motor output. Since this magnetic energy is consumed by the resistor which is the voltage control means 100 or 100', this type of AC motor has a large loss. The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a drive device that is driven by a small-capacity AC motor with little loss.

FIG. 2 is a circuit diagram showing the configuration of an embodiment of the present invention.
is a capacitor, 7 is a chopper, 8 is a diode, and 9 is a reactor.

The capacitor 6 is connected between the diode 4 and the positive terminal of the DC power supply 1, and suppresses the output of the diode 4, that is, the transient voltage of the winding 2, and absorbs and stores (charges) the accumulated magnetic energy. . When the chopper 7 is turned on in this state, the charge in the capacitor 6 is discharged via the reactor 9. Next, when the chopper 7 is turned off, the magnetic energy accumulated in the reactor 9 regenerates energy to the DC power supply 1 through the diode 8. In this series of operations, if the on-off time of the chopper 7 is controlled so that the current flowing through the reactor 9 continues, the following equation holds true.
．． bn. E, E, . ．． …． ．． 、． ．． ．． ．． ．． ．． ．． ．．
．． ．． [21Q=iF〒ear-E, 10E2 crocodile=vine...
……．・・Nimenn: Chotsupa ON time ff: Chotsupa OFF time T: Chotsupa ON-OFF cycle Q: Chopper conduction rate E,: DC power supply voltage E2: Capacitor charging voltage E3: E , 1E2, which is the output terminal potential of the diode 4.

Note that in a driving method in which the current flowing through the reactor 9 is discontinuous, the purpose is achieved by shortening the on-time ton of the chopper 7 than in the above case.

Further, regarding the capacitor 6, a pulse regeneration method may be adopted in which the capacitor 6 is discharged within one on-period of the chopper 7 so that the charging and pulsating pressure E2 does not become smooth.

In this case, the capacitor 6 is suitably an MP capacitor, an oil capacitor, a paper capacitor, or the like. FIG. 3 shows another embodiment of the present invention, in which semiconductor switches 3a to 3c are
Further, the current value is controlled by on/off control using the signal w from the second conduction control signal generator 12. That is, by controlling the on-off time ratio of the second signal w instead of the current-limiting resistor 5 of the embodiment explained in FIG. It controls the current value supplied to the phase winding 2.

Then, as a method for controlling the current value, for example, the output signal of the current detector 15 and the reference value are compared by the comparison controller 13, and the second signal w is outputted so as to maintain a constant relationship.
Constant current limit control can be performed by controlling the ON-OFF time ratio. Reference numeral 14 denotes a smoothing reactor for improving the smoothing effect of the power supply current in the above-mentioned current value control.

Note that this smoothing reactor 14 can be omitted if the inductance of the winding 2 is sufficiently large, such as in a pulse motor, or if the semiconductor switch 3 is capable of high-speed switching, such as a transistor. 11a, 11b, 1
Reference numeral 1c denotes an AND element, which controls the semiconductor switches 3a, 3b, 3c according to the AND condition of the distribution signals Sa, Sb, Sc of the first conduction control device 10 and the second signal w.

When high-frequency pulse modulation control is performed using the second signal w as in this embodiment, the current flowing through the diodes 4a to 4c further increases compared to the embodiment explained in FIG. The power recovery effect by the chopper 7 to the reactor 9 becomes even greater. FIG. 4 is a circuit diagram showing still another embodiment of the present invention, in which a thyristor is used as the semiconductor switch. In the figure, the semiconductor switch 3 is formed by a thyristor 31, a series diode 32, and an arc-extinguishing capacitor 33. Also, the AC motor windings are 2a and 2b.
Each phase is provided with windings of both forward and reverse polarity as group A and group B, respectively, and has a push-pull configuration, which is a so-called double star connection. The reactor 16 connected between the neutral points here is an interphase reactor. Reference numeral 17 is a chopper control device for controlling the power supply current value.

As described above, according to the present invention, the residual magnetic energy of the windings generated each time the semiconductor switch that feeds power from the DC power source to the AC motor windings is turned off can be recovered to the DC power source, so that a drive device with low loss can be obtained. .

That is, according to the present invention, there is a capacitor that absorbs and stores the residual magnetic energy of the winding 2 at the output end of the diode 4, a chopper that discharges the charge of the capacitor, and a capacitor that discharges the electromagnetic energy discharged from the capacitor when the chopper is turned on. It is equipped with a reactor that accumulates energy, and a diode that regenerates the electromagnetic energy accumulated in the reactor into a DC power supply when the chopper is off, and when the chopper is on, the charge on the capacitor is discharged in a circuit consisting of the capacitor, the chopper, and the actor. The electromagnetic energy of the capacitor is stored in the reactor, and when the chopper is off, the electromagnetic energy of the reactor is regenerated into the DC power supply in a circuit consisting of the reactor, DC power supply, and diode, so that the residual magnetic energy of the winding is reduced. By controlling the on/off of the chopper, the magnetic energy is transferred from the capacitor to the reactor and from the reactor to the DC power supply, which has the effect of effectively recovering magnetic energy and lowering the withstand voltage of the capacitor.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a conventional AC motor drive device, and FIGS. 2 to 4 are circuit diagrams each showing the configuration of an embodiment of the present invention. In the figure, 1 is a DC power supply, 2 is an AC motor winding, 3 is a semiconductor switch, 4 is a diode, 6 is a capacitor, and 7
8 is a diode, and 9 is a reactor. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A group of semiconductor switches each having one end connected to one end of the DC power source, and an AC motor winding having one end connected to the other end of the semiconductor switch group, and the other ends commonly connected to the other end of the DC power source. , a group of diodes each having one end connected to a connection point between the other end of the semiconductor switch group and one end of the AC motor winding, and the other end of which is commonly connected; a common connection point of the diode group and the other end of the DC power supply; a capacitor connected between one end of the semiconductor switch group and charged with electromagnetic energy of the AC motor winding via the diode group when the semiconductor switch group is shut off; one end of the capacitor connected to the common connection point of the diode group; a reactor connected between the other end of the chipper and the other end of the DC power supply, in which electromagnetic energy discharged from the capacitor is stored when the chipper is turned on; the chipper and the reactor; and one end of the DC power source, the diode regenerating the electromagnetic energy accumulated in the reactor to the DC wire when the chopper is turned off.