JPS6352693A - Speed controller for single phase induction motor - Google Patents

Abstract

PURPOSE:To apply constant voltage to a single induction motor regardless of the fluctuation of input power, by changing the pulse width of driving pulse according to current detected signal. CONSTITUTION:By a current detection means 7, the effective value of current flowing to a single phase induction motor 5 is detected. By a pulse signal conversion moans 10, according to a detected signal value from the current detection means 7, the pulse width of the signal of output generated from an oscillation means 2 is changed. As the detected signal value is increased, the pulse width is continuously reduced. By the pulse signal having the pulse width, a switching transistor 12 is ON/OFF-controlled, and current is conducted to the single pulse induction motor during the only period of the pulse width of the pulse signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a speed control device for a single-phase induction motor used to control the amount of air blown by, for example, an electric fan.

(b) Conventional technology Single-phase induction motors used for blowing air such as electric fans change their rotational speed depending on the applied AC voltage. By connecting them in series or in parallel, a constant amount of air can be obtained.

In addition, as a speed control circuit for a blower, JP-A-56-10
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. 1089.

(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. ,
In countries where different voltages, such as C and 200V, are drawn into homes, it would be dangerous if the wrong input voltage was used. Furthermore, in the latter example, the speed control is performed with respect to a constant input, and the output is not constant when the input changes.

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

(d) Means for Solving the Problems The present invention has an oscillation means that outputs a signal with a constant frequency higher than the commercial frequency, a current detection means that detects the effective value of the current flowing through the single-phase induction motor, pulse signal converting means for converting the signal output from the oscillating means into a pulse signal having a pulse width that continuously decreases as the detection signal value from the current detecting means increases; Speed control of a single-phase induction motor (I device) characterized in that it is equipped with energization control means for energizing the single-phase induction motor only during a pulse width period.

(E) The working current detection means detects the effective value of the current flowing through 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 detection signal value from the current detection means, and outputs the pulse signal to the energization control means. The pulse width decreases as the detection signal value increases. and,
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 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.

The speed control device 1 of this embodiment includes an oscillation means 2, a resistor 4, an error detection circuit 5, and an error amplification circuit 6 for detecting the effective value of the current flowing through a single-phase induction motor R (hereinafter referred to as a motor) 3.
and a comparator circuit 8 to which the oscillation means 2 and the error amplification circuit 6 are respectively connected to the input terminals.
and an amplifier circuit 9 connected to the output side of the comparator circuit 8, and an energization control means 13 consisting of a power rectifier circuit 11 consisting of four diodes and a switching transistor 12. configured. 14 is commercial electricity a.

What is shown in FIG. 2 is a specific circuit diagram of the above embodiment. The oscillation means 2 includes two operational amplifiers (hereinafter referred to as operational amplifiers) 15 and 16, resistors 17 to 20, and a capacitor 21.
It outputs a triangular wave signal S1 with a constant frequency higher than the commercial frequency. The triangular wave signal S1 is inputted to a comparator 23 via a resistor 22. The resistor 22 and the comparator 23 are composed of a resistor 24 connected to the output of the comparator 23 and a pull-up resistor 2 connected to the output.
5 constitutes a comparator circuit 8.

The output of the comparator 23 is connected to an amplification circuit 9 including a resistor 26, an amplification transistor 27, and a resistor 28 connected to the collector of the amplification transistor 27. The error amplifying circuit 6 connected to the resistor 24 includes a resistor 29 that divides the DC voltage Vcc of a DC power supply (not shown) to generate a predetermined reference value, a variable resistor 30J5, and a resistor 31 connected in series in the above order. A voltage divider circuit connected to
The differential amplifier circuit includes an operational amplifier 32 and resistors 33 to 36, and an inverting amplifier circuit includes an operational amplifier 37 and resistors 38 to 40. The output of the voltage divider circuit is connected to a resistor 34, and the output of the operational amplifier 32 is connected to a resistor 38. Further, the output of the error detection circuit 5 is connected to the resistor 33 which is connected to the single terminal of the operational amplifier 32. The error detection circuit 5 includes an analog calculation IC 41, variable resistors 42, 43, and 44, and a resistor 4, which converts the rectangular waveform voltage applied across the resistor 4 into an effective value voltage.
5, operational amplifier 46, resistors 47 to 54, and capacitor 55
and a diode 56, and amplify the effective value iIf pressure of the analog calculation IC 41.
Operational amplifier 57, resistors 58 and 59, and capacitor 60.6
1 and an amplifier circuit consisting of 1.

Next, the operation of the embodiment will be explained with reference to FIG.

The oscillation means 2 outputs a triangular wave signal S1 having a constant frequency higher than the commercial frequency of the commercial power source 14, as shown in FIG. Furthermore, a voltage v1 or a voltage v2 having a waveform shown in FIG. 3 is input to the error detection circuit 5 depending on the magnitude of the current flowing through the motor 3.

In other words, in this case, the voltage V1 is set to a state before the input voltage of the motor 3 changes, and the voltage v2 is set to a state of a variable contact. Then, the error detection circuit 5 outputs a voltage 11 which is the effective value of the voltage 11 corresponding to the voltage 1, and a voltage V21 corresponding to the voltage 2. The difference between the voltage V11 and the voltage V21 from a predetermined reference value is calculated by the error amplification circuit 6, and therefore, the output voltage v3 of the error amplification circuit 6 is within the maximum value of the triangular wave signal S1 by the voltage of each difference. Change. Here, it is assumed that the output voltage v3 corresponding to the voltage 11 is the voltage V31, and the output voltage v3 corresponding to the voltage 21 is the voltage V32.

Now, if the input voltage of motor 3 decreases, that is, resistance 4
A case will be explained in which the voltage across the voltage V1 changes from the voltage V1 to the voltage ■2.

In this case, the output of the error detection circuit 5 also decreases from the voltage V11 to the voltage V21. Correspondingly, the output of the error amplifier circuit 6 also decreases from the voltage V31 to the voltage V32. The voltage V32 is then compared with the triangular wave signal S1 of the oscillation means 2 in the comparator circuit 8, and converted into a pulse signal Sp having a pulse width P1 corresponding to fluctuations in the input voltage. Here, compared to before the input voltage change, the duty ratio of variable II becomes larger because the output voltage v3 decreases. The pulse signal Sp is amplified by the amplifier circuit 9 and then input to the switching transistor 12. This causes the switching transistor 12 to switch, and the motor 3 is energized only during the pulse width P1 of the pulse signal Sp. S2 is a voltage waveform at the collector of the switching transistor 12. Therefore, the voltage applied to the motor 3, which is effectively a load, is kept constant.

Further, even when the withstand current (load current) flowing through the motor 3 decreases, the current is converted into voltage by the resistor 4, so that the same operation as described above occurs.

Next, when the input voltage increases and the load current increases, the level of the output voltage v3 increases, so the duty ratio of the pulse signal Sp becomes smaller (the pulse width becomes smaller), and therefore the effective The voltage applied to the motor 3 is now reduced.

In addition to the above, in this embodiment, by adjusting the variable resistor 30 of the error amplification circuit 6, the voltage applied to the motor 3 can be adjusted steplessly when the input voltage is constant.

That is, by adjusting the variable resistor 30, the output voltage (3) of the error amplification circuit 6 continuously increases and decreases. As a result, the duty ratio of the pulse signal Sp output from the pulse signal converting means 10 changes, as in the case of the above-mentioned input voltage fluctuation, and as a result, for example, when the output voltage V3 is the voltage V31, the duty ratio of the pulse signal Sp that is applied to the motor 3 is changed. The voltage is effectively reduced.

Conversely, if the resistance value of the variable resistor 30 is increased to reduce the output voltage v3, the duty ratio of the pulse signal Sp increases, and the voltage applied to the motor 3 effectively increases. As described above, the rotation and speed of the motor 17 can be continuously varied.

(G) Effects of the Invention According to the present invention, there is provided a speed control device for a single-phase induction motor that achieves the effects listed below.

(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 different 1-voltage commercial power sources.

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

(・1) Compared to the phase control method, no electromagnetic noise is generated because the energization is controlled at a frequency higher than the commercial frequency.

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

(6) Since error detection is performed using current, it is possible to prevent an increase in load current when the motor is locked.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of the embodiment, and FIG. 3 is a signal waveform diagram showing the relationship between the respective signals when the input voltage decreases. 2... Oscillation means, 3... Single phase induction motor, 7... Current detection means, 10... Pulse signal conversion means, 13...・
・Electrification control means. Figure 1

Claims (1)

[Claims] 1. Oscillation means for outputting a signal with a constant frequency higher than the commercial frequency, current detection means for detecting the effective value of the current flowing through the single-phase induction motor, and current detection means for detecting the signal output from the oscillation means. a pulse signal converting means for converting the detected signal from the means into a pulse signal having a pulse width that continuously decreases as the value increases; and a single-phase induction motor for only the period of the pulse width of the pulse signal output by the pulse signal converting means. 1. A speed control device for a single-phase induction motor, comprising: energization control means for energizing. 2. The current detection means includes an error detection circuit that converts the effective value of the current flowing through the single-phase induction motor into an effective value voltage, and an error amplification circuit that calculates the difference between the output signal of the error detection circuit and a predetermined reference value. A speed control device for a single-phase induction motor according to claim 1, comprising: