JPS61214794A - Variable speed motor - Google Patents

Abstract

PURPOSE:To remove a starter and to reduce a starting current by displacing a current phase flowing to a main winding and a starting winding at 90 deg.. CONSTITUTION:The main winding 8 and the starting winding 9 of an induction machine are independently driven by single-phase bride inverters 10, 11. Accordingly, when semiconductor switches of the inverters 10, 11 are energized or interrupted by the prescribed frequency, two voltage phases can be arbitrarily altered as shown in Fig. (a) as the voltage waveform 13 applied to the winding 8. When the pulse width control of the inverter is executed, an ideal sinusoidal wave approximate waveform is obtained as shown in Fig. (b) to improve the motor characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to variable speed of a single-phase induction machine, and particularly to a two-phase inverter that can omit a starting device.

[Background of the invention]

In the conventional device, as shown in FIG. 1, a DC power source 2 was simply converted into AC power through a single-phase bridge type inverter 1. Therefore, the main winding 4 or starting winding 5 of the single-phase induction machine 3 is the same as before.

The running capacitor 6 and the starting bag W7 remain connected. Therefore, when starting the motor, a large current flows.2This starting rating determines the capacity of the inverter element. It should be noted that there are no known documents related to this type of device, and Japanese Patent Application No. 59-69054 is listed in the applicant's prior order.

[Purpose of the invention]

The purpose of the present invention is to provide a variable speed induction machine system that eliminates the starting device of a single-phase induction machine and reduces the starting current = [Summary of the Invention] In general, a single-phase induction machine has a starting torque of zero. Yes, special activation device is required. The purpose of this is to shift the phase of the current flowing through the main winding and the starting winding by 90".
On the other hand, if the current phases of the two windings can be shifted by 90 degrees using another method, the starting device becomes unnecessary. In view of this point, the present invention optimizes the characteristics during startup and operation by independently controlling the phase of the voltage applied to the main winding and the startup winding using an inverter.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Although the principle of the invention is the same in this embodiment, the configuration is different from the scope of the claims.

In FIG. 1, the main winding 8 and starting winding 9 of the induction machine are independently driven by single-phase bridge inverters 0 and 11, respectively. Therefore, if each semiconductor switch of the inverter is energized and cut off at a predetermined frequency.

As shown in FIG. 2(a), the two voltage phases can be changed arbitrarily, such as the voltage waveform 12 applied to the main winding 8 and the voltage waveform 1°3 applied to the starting winding 9. be. Furthermore, if the inverter pulse width is controlled, the
), an ideal sine wave approximation waveform is obtained and the motor characteristics are improved.

A second embodiment of the invention is shown in FIG. In FIG. 1, eight semiconductor switches are required, but in FIG. 3, only four are required. To explain the operation shown in Figure 3, first, the single-phase induction machine 1
When the semiconductor switch 19 closes, a voltage is applied to the main winding 15 of No. 4 from the power source 17. In the next half cycle, after closing semiconductor switch 19, semiconductor switch 2
0, a reverse voltage is applied from the power supply 18 to the main winding 15, and as a result, the power supply 17 is applied to the main winding lllA15.
and 18 as well as semiconductor switches 19 and 20, the second
A rectangular wave AC voltage as shown in FIG. 12 is applied.

Similarly, a rectangular AC voltage as shown in FIG. 2(a) 13 is applied to the starting winding 16 by power supplies 17 and 18 and semiconductor switches 21 and 22. .

The phases of the voltages applied to these two windings can be controlled independently. Furthermore, by controlling the pulse width of each semiconductor switch, it is possible to form an approximate sinusoidal current as shown in FIG. 2(b).

Note that even when using a general commercial power source, the power sources 17 and 18 can be easily created using a voltage doubler rectifier circuit or the like.

〔Effect of the invention〕

According to the present invention, it is possible to provide a single-phase induction variable speed device that does not require a starting device, optimize the voltage and current phase of the main winding and starting winding of the induction machine, and enable low frequency starting. Therefore, it is possible to reduce the starting current.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a first embodiment of the present invention;
Figure 2 shows voltage and current waveforms that can be formed by the circuit in Figure 1, Figure 3 is a circuit block diagram of the second embodiment of the present invention, and Figure 4 is a circuit block diagram of a conventional single-phase induction motor variable speed system. It is a diagram. DESCRIPTION OF SYMBOLS 1...Single-phase bridge type inverter, 2...DC power supply, 3...Single-phase induction machine, 4...Main winding, 5...Starting winding, 6...Running capacitor, 7 ... Starting device, 8... Main winding, 9... Starting winding, 10.11.
... Single-phase bridge type inverter, 12.13... Applied voltage waveform to winding, 14... Single-phase induction machine, 15...
Main winding, 16... Starting winding, 17.18... Power supply,
19, 20, 2]. 22...Semiconductor switch. /”～

Claims (1)

[Claims] In a variable speed motor consisting of a single-phase bridge type inverter consisting of four semiconductor switches, two DC power supplies connected in series, and a single-phase induction machine consisting of a main winding and a starting winding, two of the inverters One of the output terminals of the inverter is connected to the induction machine main winding, the other output terminal of the inverter is connected to the induction machine starting winding, and the other terminal of the main winding and the starting winding is connected to the DC power supply. A variable speed electric motor characterized in that it is connected to a series connection point of.