JPS6352692A - Speed controller for single phase induction motor - Google Patents

Abstract

PURPOSE:To apply constant voltage to a single phase induction motor regardless of the fluctuation of input power, by detecting voltage applied to windings, and by changing the pulse width of driving pulse according to its detected signal. CONSTITUTION:By a detecting winding 17b wound up in parallel with a main winding 17a, voltage applied to the pain winding 17a is detected. By a pulse signal conversion means 26, according to the detected signal value of the voltage, the pulse width of the signal of output generated from an oscillation means 1 is varied. As the detected signal value of the voltage gets larger, the pulse width is made smaller. By a switching transistor 27, current is conducted to a single phase induction motor 17 during the only period of the pulse width of the pulse signal.

Description

DETAILED DESCRIPTION OF THE INVENTION B) Industrial Application Field This invention relates to a speed control device for a single-phase induction motor used in a blower such as the 7iffli.

(b) Conventional technology A single-phase induction motor used in a blower such as an electric fan changes its rotational speed depending on the applied AC voltage. Alternatively, they are configured so that a constant air flow ω can be obtained by connecting them in parallel. In addition, as a speed control circuit for a blower, JP-A-56-101
There is also known a motor which continuously controls the rotational speed of a single-phase induction motor according to changes in suction temperature, as disclosed in Japanese Patent No. 089.

(c) Problems to be Solved by the Invention However, in the above-mentioned device in which the switch is changed by the user each time, it is troublesome to operate the switch, and there are other problems.

In countries where different voltages such as A, C, 100V and A, C, 200V are drawn into homes, it is dangerous to use the wrong input voltage. In addition, in the example of the winner, speed control for a constant input,
When the input changes, the output does not remain constant.

This invention has been made in view of the above circumstances, and therefore aims to provide a speed control device for a single-phase induction motor that can apply a constant voltage to the single-phase induction motor regardless of fluctuations in input voltage. .

(d) Means for Solving the Problems This invention provides an oscillation means that outputs a signal with a constant frequency higher than the commercial frequency, and a voltage detection means that detects the voltage applied to the winding of a single-phase induction motor. , a pulse signal converting means for converting the signal output from the transmitting means into a pulse signal having a pulse width that continuously decreases as the detection signal value from the voltage detecting means increases; and a pulse signal output from the pulse signal converting means. 1. A speed control device for a single-phase induction motor, characterized in that it is equipped with energization control means for energizing zero single-phase induction lightnings only during a period of a pulse width of .

(E) The operating voltage detection means detects the voltage applied to the winding of the single-phase induction motor, and outputs a detection signal to the pulse signal conversion means.

The pulse signal conversion means converts the signal from the oscillation means into a pulse signal having a pulse width corresponding to the detected signal value, and outputs the pulse signal to the energization control means. The pulse width is decreased as the detection signal value increases. Then, the energization control means applies a constant voltage by energizing the single-phase induction motor only during a period of the pulse width of the pulse signal, thereby rotating the single-phase induction S motor at a constant speed.

(F) EXAMPLES Hereinafter, examples of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following examples.

In FIG. 1, reference numeral 1 denotes an oscillation means, which is composed of a rectangular wave oscillation circuit 6 consisting of resistors 2 to 4 and an operational amplifier (hereinafter referred to as an operational amplifier) 5, resistors 7 and 8, a capacitor 9, and an operational amplifier 10. 1, and a resistor 12 connected to the output of the integration circuit 11 and the input of the rectangular wave oscillation circuit 6, and outputs a triangular signal S1. 13 and 14 are voltage dividing resistors that generate an input voltage for the rectangular wave oscillation circuit 6, and the resistor 13 receives a DC voltage Vcc from a DC power supply (not shown). The triangular wave signal S1, which is the output signal of the JOB means 1, is inputted to the ten input terminal of the comparator 16 via the resistor 15. One input terminal of the comparator 16 is connected to a detection winding 17b, which is a voltage detection means, wound in parallel to the main wire 17a of a single-phase induction motor (hereinafter referred to as motor) 17, and connected in series to the detection winding 17b. An error detection circuit 22 includes a diode 18 connected to the diode 18, a variable resistor 19 connected in series to the diode 18, and a parallel circuit of a resistor 20 and a capacitor 21 connected in series to the variable resistor 19. It is connected via a resistor 23. The output terminal of the comparator 16 is connected to the base of an amplifying transistor 25 via a resistor 24. The comparator 16, the resistor 24, and the amplification transistor 25 constitute a pulse signal conversion means 26. 27 is a switching transistor whose base is directly connected to the emitter of the amplification transistor 25. Reference numeral 28 denotes an electric FA rectifier circuit, which is composed of a full-wave rectifier bridge circuit using four diodes. One input end 28a is connected to a commercial power supply 29, and the other input end 28b is connected to the motor 17. Ru. Further, one output end 28c is connected to the collector of the switching transistor 27, and the other output end 28d is connected to the ground 30. The switching transistor 27 and the power supply rectifier circuit 28 constitute an energization control means 31. Note that an auxiliary winding 17c and a capacitor 32 connected in series are connected in parallel to the main winding 17a of the motor 17.

Next, the operation of the embodiment will be explained with reference to FIGS. 2 to 4.

The oscillation means 1 integrates the rectangular wave s2 shown in FIG. This is what is output. Further, the output voltage Ve of the error detection circuit 22 is
The voltage level corresponds to the voltage applied to a. Then, the triangular wave signal S1 and the output voltage Ve are compared by the comparator 16 of the pulse signal converting means 26, and
As shown in FIG. 2, a pulse signal Sp of a predetermined width is outputted in accordance with the output voltage e. In other words, when the voltage applied to the motor 17 increases, the detection signal value of the output signal of the detection winding 17b increases, and therefore the output voltage Ve of the error detection circuit 22 increases, as shown in FIG. 2B. The pulse width P1 of the pulse signal Sp becomes smaller. On the contrary, when the voltage applied to the motor 17 decreases, the output voltage Ve of the error detection circuit 22 also decreases, and the pulse width P2 increases as shown by Δ in FIG. 2.

The pulse signal Sp is amplified by the amplification transistor 25 and causes the switching transistor 27 to switch. As a result, when the output voltage Ve is low, as shown in FIG.
, the commercial 3!29 voltage is converted to DC, and a voltage V1 is generated that is conductive only during a period of pulse width P2. Therefore, the motor 17 is energized only during the period of this pulse width P2.

Next, when the input voltage of the motor 1a increases from the above state, the voltage induced in the detection winding 17b also increases, that is, the detection signal value increases, and the output voltage Ve of the error detection circuit 22 increases. As a result, the pulse signal converting means 2
The pulse width (or duty ratio) of the pulse signal @Sp generated by No. 6 becomes smaller, so the voltage V1 changes, effectively lowering the voltage applied to the motor 17, and causing the motor 17 to have an effective A constant voltage will be applied to.

In addition to the above, in this embodiment, by adjusting one variable resistor of the error detection circuit 22, the voltage applied to the motor 17 can be adjusted steplessly when the input voltage is constant.

That is, by adjusting the variable resistor 19, the third
As shown in the figure, the output voltage Ve of the error detection circuit 22 continuously rises and falls between the level L level L2. As a result, the duty ratio of the pulse signal Sp output from the pulse signal converting means 26 changes, as in the case of the input voltage fluctuation, and as a result, for example, when the output voltage VO is at level L1, one of the power source rectifying circuits 28 A voltage V11 is generated at the output terminal 28c of the motor 17, and the voltage applied to the motor 17 is effectively reduced. Conversely, if the resistance value of the variable resistor 19 is increased to bring the output voltage Ve to the level L2, the duty ratio of the pulse signal Sp increases, and a voltage V12 is generated at one output terminal 280, causing the motor 17 The voltage applied to becomes effectively larger. As above,
The rotational speed of the motor 17 can be varied continuously.

In the above embodiments, a detection winding provided in the motor is used as the voltage detection circuit, but a potential transformer (PT) or the like may also be used. Further, a control semiconductor such as a thyristor may be used instead of the switching transistor.

(g) Effects of the Invention According to the present invention, a speed control device for a single-phase induction motor that achieves the effects listed below can be obtained.

(1) The motor can be rotated at a constant speed regardless of input voltage fluctuations.

[2] Motors without motor windings, such as those for 100V and 200V, can be used with commercial power supplies of different voltages.

(3) There is no danger even if the motor power supply voltage is incorrectly used.

(4) Compared to the phase control method, since the energization is controlled at a frequency higher than the commercial frequency, no electric current Eft M is generated.

(5) No speed adjustment tap is required on the winding of the motor used.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an embodiment of the present invention, Fig. 2 △ and B show signal waveform diagrams showing the relationship between the signals J3 when the input voltage drops and when the input voltage rises, respectively. Fig. 3 shows the variable resistance FIG. 3 is a signal waveform diagram showing the relationship between the respective signals when the device is adjusted. 1...Oscillation means, 17...Single-phase induction motor, 1ab...Detection winding (voltage detection means)
, 26...pulse signal conversion means, 31...
...Electrification control means.

Claims (1)

[Claims] 1. An oscillating means for outputting a signal with a constant frequency higher than the commercial frequency, a voltage detecting means for detecting the voltage applied to the winding of a single-phase induction motor, and a signal output from the oscillating means. A pulse signal converting means converts the detected signal from the voltage detecting means into a pulse signal having a pulse width that continuously decreases as the value increases, and the pulse signal converting means outputs a single phase signal only during the pulse width period of the pulse signal. 1. A speed control device for a single-phase induction motor, comprising energization control means for energizing the induction motor. 2. The speed control device for a single-phase induction motor according to claim 1, wherein the voltage detection means is a detection winding provided in parallel with the winding of the single-phase induction motor.