JPS6041833Y2 - Current source inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter device that converts DC power to AC power, and particularly relates to a current source inverter device with an improved output current waveform.

A problem with variable speed control of the motor by supplying a square wave current to the load AC motor with a conventional 1200 current type current controlled inverter device is that the harmonics contained in the output current are relatively large. , the output torque ripple of the load motor becomes large.

Particularly when speed control is performed in a low frequency range, the pulsation of the output torque makes accurate control impossible, and the output efficiency of the load motor also decreases.

As a method for reducing this problem, that is, harmonic components, two sets of current-controlled inverter circuits I as shown in FIG.
There is a method of driving the motor M by connecting NVI and INV2 in parallel and setting the phase difference between them to θ as shown in FIG.

However, when driving the electric motor M with the current control type inverter shown in FIG.
If the load power factor angle is φ, the voltages EdIV and Ed2V of DC power supplies Ed□ and Ed2 are θ Ed□=1.35EMCO3 ($ -7) ---
---(1) θ Ed2 = t35EMCO3 (φ10-)...
...(2), and when the power factor is close to 1, there is not much of a problem, but when the power factor is bad, there are cases where Ed>Ed2,
DC power supply Ed1. Ed2 is required to have a different power supply capacity and output voltage value.

Furthermore, when the phase angle θ of current-controlled inverter circuits INVl and INV2 is increased, currents overlap when the thyristors commutate in an actual device, and thyristor U of current-controlled inverter circuit INVl and current-controlled inverter circuit There is a risk that the thyristor X of INV2 overlaps and becomes conductive, and unless the DC voltage d□ and Ed2 are electrically insulated, the operation of the device will become unstable.

Furthermore, the control circuit for controlling the phase angle θ becomes complicated.

Therefore, the present invention has been made in view of the above points, and it is an object of the present invention to provide a current source inverter device in which the DC power sources Ed and Ed2 can be used as a common power source, and the phase angle θ can be arbitrarily controlled. purpose.

Hereinafter, one embodiment of the present invention will be briefly described with reference to the drawings.

Figure 3 shows the constituent countries of an embodiment of the present invention, with rectifier Rf
Connect current control type inverter circuit (hereinafter simply referred to as inverter circuit) INV1 and INV2 to the output terminal of
Each inverter circuit INV l.

The output terminal of INV2 is connected in parallel to the electric motor M via inverter transformers T1 and T2.

By configuring as described above, the inverter circuit IN
Thyristors U, X1v and Y between V l and INV2
, even if the energization periods of W and Z overlap, the inverter transformer T□
Since it is insulated by T2 and T2, the phenomenon of unstable operation of the device can be eliminated.

(Even if the thyristor X of the inverter circuit INV2 is conducting when the thyristor U of the inverter circuit INVl starts conducting, a short-circuit current loop that flows from the power supply positive bus line to the load line via the two thyristors U and X does not occur).

Also, even if a common DC bus is used, inverter transformers T1 and T
By differentiating the primary side voltages of the two, the above-mentioned inconvenience does not occur.

FIG. 4 shows another embodiment of this invention.

In FIG. 4, the same effect as the circuit system of FIG. 3 can be obtained by dividing the primary winding of one inverter transformer T in the inverter transformers T□ and T2 of FIG. 3.

In Figures 3 and 4, when combining the current flowing from each inverter circuit, the operating phase difference θ of each inverter circuit can be controlled to a predetermined value, and the primary side connections of each inverter transformer can be By adopting any connection method such as Δ connection or Y connection, the phase difference (θ + δ) is the sum of the operating phase difference θ of each inverter circuit and the phase difference δ caused by the difference in the primary side connection of the transformer. The inverter output current can be synthesized by

At this time, when the phase difference θ is zero and control is performed, the phase difference between the output currents of each inverter becomes δ in FIGS. It has the advantage of being able to supply

According to this invention, the following effects and advantages can be obtained.

(1) Since the output current of each inverter circuit is insulated and covered, even if the phase angle θ is arbitrarily selected, the operating condition of one inverter circuit will not affect the other inverter circuit, resulting in stability and reliability. It can be a high-performance device.

(2) Since the output voltages of each inverter circuit can be different by changing the primary voltage of each inverter transformer, a common DC power source can be used.

As a result of the above effects, it is possible to provide a current control type inverter device which has excellent controllability such as small torque ripple during low speed operation and is highly reliable.

[Brief explanation of drawings]

FIG. 1 shows the constituent countries of the conventional device, FIG. 2 shows waveform diagrams of various parts of FIG. 1, and FIGS. 3 and 4 show the constituent countries of different embodiments of the present invention. INVl, INV2. INV3...Current control type inverter circuit, Rf, Rfl, Rf2...
- Rectifier circuit, T. T1. T2...Inverter transformer, T3...
...Input transformer, M...Load AC motor, E
dl, Ea, ...DC power supply.

Claims (1)

[Scope of utility model registration request] The input sides of at least two sets of current-controlled inverter circuits are commonly connected, the output sides are insulated and connected in parallel via an inverter transformer, and the output phases of the inverter transformers are shifted by a predetermined phase to vary the power factor. A current source inverter device characterized by driving a load.