JPH0783633B2 - Pulse width modulation type single-phase motor inverter - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pulse width modulation type single-phase motor inverter.

(Prior Art) A pulse width modulation type motor inverter, in which a semiconductor switch is turned on and off many times by a pulse width modulation signal to adjust an output voltage and an output frequency, has been conventionally known for a three-phase motor. .

That is, FIG. 3 shows a basic circuit of a three-phase pulse width modulation type inverter, in which each of the transistors 1, 2, 3, 4, 5 and 6 is turned on and off every half cycle by a pulse width modulation signal, and a DC power source 7
Supplies the three-phase AC voltage to the three-phase motor 8. The pulse width modulation signal is obtained from the pulse generation circuit connected to each of the transistors 1, 2, 3, 4, 5 and 6, but the pulse generation circuit has many fundamental wave components of the inverter output voltage and It is close to a sine wave.

When the voltages at points A, B, and C in FIG. 3 are represented by vectors, they are equivalent to voltages that are out of phase by 120 ° as in FIG. 4, and in the case of the three-phase motor 8, this is If a voltage with a phase difference of 120 ° is applied to each winding, a rotating magnetic field is generated and the three-phase motor 8 can be rotated. This applies to both the star connection shown in FIG. 3 and the delta connection shown in FIG.

The vector voltages U, V, W between AB, BC, and CA are also shifted by 120 °.

In the case of the single-phase motor 9, when a voltage with a phase difference of 90 ° is applied to the main winding 10 and the auxiliary winding 11, a rotating magnetic field is generated to rotate, so that the windings 10 and 11 are shown in FIG. If connected in this way, the voltage at point C becomes a vector in the opposite direction to the voltage at point A, as shown in FIG. 7, so that vector voltages U and X are orthogonal, and therefore the three-phase inverter can be used as is. Thus, the single-phase motor 9 can be rotated.

(Problems to be Solved by the Invention) However, although the circuit of FIG. 6 can be used for the single-phase motor 9, it requires a semiconductor switch, that is, six transistors. An additional circuit must be provided for each transistor, and therefore, the structure is complicated and expensive despite the single-phase motor 9.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to reduce the number of semiconductor switches by utilizing the fact that they are single-phase motors, and to enable simple and inexpensive implementation.

(Means for Solving the Problem) As a means for solving the problem, the present invention alternately turns on and off 2
The first circuit 24 and the second circuit 25, which are formed by connecting the semiconductor switches 26, 27, 28, 29 in series, are provided in parallel, and both ends of the main winding 22 of the single-phase motor 21 are connected to the first circuit 24 and the second circuit 25. It connects between each semiconductor switch 26,27,28,29 with 2 circuits 25, and both ends of the auxiliary winding 23 of the single phase motor 21 are connected to the intermediate tap of the main winding 22 and the voltage dividing point of the DC power supply 20. It was done.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a vector diagram thereof. In FIG. 1, 20 is a DC power supply, 21 is a single-phase motor, and has a main winding 22 and an auxiliary winding 23. Reference numeral 24 is a first circuit, and 25 is a second circuit, which are configured by connecting transistors 26, 27, 28, 29 as semiconductor switches in series and are connected in parallel with each other. Then, the transistors 26, 27, 2 of these circuits 24, 25
Both ends of the main winding 22 of the single-phase motor 21 are connected to points A and B between 8 and 29.

Then, using the main winding 22 of the single-phase motor 21, an intermediate tap E ′ is provided at a position where the winding ratio is 1: 1 on the main winding 22, and the auxiliary winding 23 is provided on the intermediate tap E ′. Are connected.

With this configuration, as shown in FIG.
Since the voltage vector DE 'at the point E'is orthogonal to AB, the single-phase motor 21 can be rotated.
Therefore, the number of transistors is reduced to four as compared with the conventional one, so that the configuration including the attached circuit and the like can be simplified and the cost can be reduced. Moreover, in this case, since the phase of the auxiliary winding 23 is shifted, members such as a capacitor and a transformer are not required, and the cost can be further reduced.

(Effect of the Invention) In the present invention, two semiconductor switches that are alternately turned on and off
First circuit 24 and second circuit formed by connecting 26, 27, 28, 29 in series
25 in parallel with each other, and the two ends of the main winding 22 of the single-phase motor 21 are connected to the respective semiconductor switches 26, 27, 28, of the first circuit 24 and the second circuit 25.
Since it is connected between 28 and both ends of the auxiliary winding 23 of the single-phase motor 21 are connected to the intermediate tap of the main winding 22 and the voltage dividing point of the DC power source 20, the number of semiconductor switches is reduced to four. Moreover, members such as a capacitor and a transformer for shifting the phase of the auxiliary winding 23 are unnecessary. Therefore, the structure is very simple, easy to manufacture and inexpensive to implement.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is the same vector diagram, FIG. 3 is a conventional three-phase circuit diagram, FIG. 4 is the same vector diagram, and FIG. A wiring diagram of the motor, FIG. 6 is a conventional single-phase circuit diagram, and FIG. 7 is a vector diagram of the same. 20 …… DC power supply, 21 …… Single-phase motor, 22 …… Main winding, 23
...... Auxiliary winding, 24 ...... First circuit, 25 ...... Second circuit, 26-
29: Transistor (semiconductor switch).

Claims (1)

[Claims] 1. A pulse width modulation type single phase motor inverter, wherein a semiconductor switch is turned on and off by a pulse width modulation signal to supply an alternating voltage from a direct current power source (20) to a single phase motor (21). A first circuit (24) and a second circuit (25), which are two semiconductor switches (26) (27), (28) (29) that are turned on and off connected in series, are provided in parallel, and a single-phase motor (21 ) Each of the main switches (22) of the semiconductor switch (26) of the first circuit (24) and the second circuit (25)
Connect between (27), (28) and (29) and connect both ends of the auxiliary winding (23) of the single-phase motor (21) to the center tap of the main winding (22) and the voltage dividing point of the DC power supply (20). An inverter for a pulse width modulation type single-phase motor characterized by being connected to and.