JPH04295297A - Rotational speed controller for blower motor - Google Patents

Abstract

PURPOSE:To suppress running cost to a minimum by improving power factor during high torque in a rotational speed controller for blower motor. CONSTITUTION:When a regulated voltage of a voltage regulation circuit 110 becomes maximum, a power transfer circuit 118 for transferring voltage applied to an induction motor 78 from an inverter output circuit 111 to the commercial power source is provided.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational speed control device for a blower motor that changes the amount of air passing through the blower by combining an induction motor and a blower such as a sirocco fan or a propeller fan.

0002

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional rotational speed control device for a blower motor, which is disclosed in "Electronic Technology (published by Nikkan Kogyo Shimbun, 1988)". This conventional device includes a power supply circuit 1 consisting of a power transformer 2 and a rectifier 3;
A zero cross detection circuit 4 consisting of a transistor 5, a diode 6, a current limiting resistor 8 and a voltage dividing resistor 9, and an inverted output I
The output oscillation circuit 10 includes a current limiting resistor 16, an output transistor 17, and a voltage dividing resistor 18, and a power circuit section 19 includes a triac 20 and an induction motor 21.

Next, the operation of the above configuration will be explained. A power supply voltage (for example, 10
When 0V) is input, the voltage is reduced and converted into a DC voltage by the rectifier 3. At the same time, the diode 6 of the zero-cross detection circuit 4 oscillates due to the current limited by the current limiting resistor 8, turning the transistor 5 on and off. The voltage generated across the voltage dividing resistor 9 by turning on and off the transistor 5 is input to the signal input section 13 of the inverting output IC 11. The inverted output IC 11 to which power is supplied by the (+) power input section 12 and the (-) power input section 14 is connected to the signal input section 1.
The inverting output section 15 is turned on and off every cycle based on the input signal to the input signal 3, and the output transistor 17 connected via the current limiting resistor 16 is turned on and off. 18 is applied to the gate 22 of the triac 20 in the power circuit section 19.
and turns the triac 20 on and off. Through the above operations, the voltage to the induction motor 21 is turned on and off, and the rotation speed of the induction motor 21 is controlled.

0004

[Problem to be Solved by the Invention] Since the conventional rotation speed control device for a blower motor is constructed as described above,
Since the voltage applied to the induction motor 21 is a rectangular wave output, the power factor is worse than that of a sine wave output and is particularly noticeable at high torque, so a reactor must be incorporated to improve the power factor. The problem was that there were many cases where costs were forced to increase. This invention was made to solve the above problems,
The object of the present invention is to obtain a rotation speed control device for an electric blower motor that improves the power factor at high torque and minimizes running costs.

[0005]

[Means for Solving the Problems] A rotation speed control device for a blower motor according to the present invention transfers the voltage applied to the induction motor from the inverter output circuit to the commercial power supply when the regulated voltage of the voltage regulation circuit reaches the maximum. It is equipped with a power supply switching circuit.

[0006]

[Operation] The power supply switching circuit of the rotation speed control device for a blower motor in this invention switches the voltage applied to the induction motor from the inverter output circuit to the commercial power supply when the voltage regulation circuit reaches its maximum. Aims to improve power factor during torque.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a rotation speed control device for a blower motor in one embodiment of the present invention. In the figure,
109 is a power supply circuit consisting of a power transformer 106, a rectifier 107 and a smoothing capacitor 108; 110 is a diode bridge 112; a phototransistor 38;
Timing oscillation circuit 44, photo triac 45, triac 50, voltage dividing resistors 31, 32, 41, 43, 4
8, 49, a voltage adjustment circuit comprising a current limiting resistor 37 and a transistor 42 and adjusting the power supply voltage by phase control.

113 is a diode bridge, 100 is a frequency oscillation circuit, 82, 98, 99 are counter ICs, 8
7 is a current limiting resistor, 88 is a transistor, 89 is a voltage dividing resistor, 111 is a phototransistor 58, 61, 64,
67, an inverter output circuit consisting of power transistors 71, 73, 75, 77 and current limiting resistors 70, 72, 74, 76 and converting the output of the rectifier 107 into alternating current; Auxiliary C contact 11 is a power switching relay that operates when
6C1 and 116C2 together with the power supply switching circuit 118
is doing. 78 is a single-phase or three-phase induction motor,
A blower consisting of a sirocco fan or a propeller fan is installed. 79 is a coil, and 80 and 81 are capacitors. Note that the terminals a, b, c, and d are connected with the same reference numerals.

Next, the operation of the rotation speed control device for a blower motor in one embodiment of the present invention constructed as described above will be explained. First, the power supply voltage (for example, 100V
) is input, the power transformer 1 of the power circuit 109
The voltage is reduced at 06, converted to a DC voltage by a rectifier 107, smoothed by a smoothing capacitor 108, and this smoothed DC low voltage is supplied between a and b. On the other hand, the input AC voltage is divided by the voltage dividing resistors 31 and 32 and input to the diode bridge 112, and the half-wave rectified voltage flows through the current limiting resistor 37 to the diode of the phototransistor 38 to 39. A signal synchronized with the cycle of the transistor 40 controls the voltage generated in the voltage dividing resistor 41 as the transistor 40 turns on and off controls the transistor 42, and thereby the voltage signal generated in the voltage dividing resistor 43 is controlled by the timing oscillation circuit 44.
It is input to the oscillation pulse and serves as the reference for the oscillation pulse.

Furthermore, since power is input to the power input ports 103 and 104 of the timing oscillation circuit 44 via the terminals a and b, the output port 105 is the (-) power source b.
The terminal is turned on and off, the diode 46 is also turned on and off, and the triac 47 is turned on and off. At this time, the voltage dividing resistor 48
, 49 controls the gate 51 of the triac 50, and an AC voltage with a partially cut sinusoidal waveform is input to both ends of the diode bridge 113. Here, the capacitors 80 and 81 and the coil 79 are provided to prevent noise when the triac 50 generates a voltage. Further, the voltage half-wave rectified by the diode bridge 113 is supplied to the inverter output circuit 111.

Next, regarding the operation of the phototransistors 58, 61, 64, and 67 of the inverter output circuit 111,
The switching frequency of the inverter output circuit 111 is 5
A case where the frequency becomes 0 Hz will be explained as an example. First, power input ports 101 , 102 ,
When power is input from the a and b terminals of the power supply circuit 109 to the power input ports 91 and 92 of the counter IC 82 and the power input ports 94 and 95 of the counter IC 99, respectively,
The frequency oscillation circuit 100 generates a preset frequency (50H
z) oscillates at twice the frequency. When this 100Hz oscillation pulse is input to the input port 86 of the counter IC 82,
A pulse with one cycle of on and off is generated 50 times from the output port 85 of the counter IC 82, and the transistor 88 is turned on and off via the current limiting resistor 87, and the voltage generated by the voltage dividing resistor 89 connected to this transistor 88 is applied to the counter. It is input to input port 90 of IC98.

In this case, when the transistor 88 is turned on, a current flows through the terminal b, so that the input port 90 becomes a low level, which is inverted from the output port 85. At the same time, output port 85 is connected to input port 96 of counter IC 99. Furthermore, due to internal time constants, the counter ICs 98 and 99 almost interlock with the counter IC 82 when they are on, but there is a slight delay (about 3 msec) when they are off. A waveform diagram of the above operation is shown in FIG. 2, where (a) shows the output of the counter IC82;
(b) is the output of the output port 93 of the counter IC98, (
c) is the output of the output port 97 of the counter IC99, (d)
) indicates the voltage applied to the induction motor 78.

That is, the transistors 60 and 59 are turned on via the diodes 59 and 58, and the current limiting resistors 70 and 76 are turned on.
When the power transistors 71 and 77 are turned on via
A voltage flow is generated as indicated by the dashed arrow in the figure. Also, in the next cycle, the transistor 66 is connected via the diodes 65 and 62.
, 63 are turned on, power transistors 75 and 73 are turned on via current limiting resistors 74 and 72, and a voltage flow as indicated by a solid line arrow occurs. On the other hand, by detecting the output voltage of the diode bridge 113, the voltage variable resistor 117
The power switching relay 116 operates when the voltage exceeds the divided voltage generated from the coil impedance of the power switching relay 116 (for example, maximum voltage 100V).
is turned on, the power supply switching relay 116
The auxiliary C contacts 116C1 and 116C2 operate,
That is, the power supply switching circuit 118 converts the rectangular wave voltage from the inverter output circuit 111 to the commercial power supply (100V
sine wave) is performed.

By repeating the above operations, the rectangular wave voltage shown in FIG. 2(d) is applied to the induction motor 78. The height of this rectangular wave is determined by the voltage adjustment circuit 110 using phase control.
This is the rectified and smoothed value of the adjustment voltage.To increase the rotation speed, the peak value is increased, and to decrease the rotation speed, the peak value is lowered. The switching (reversal) time in this case is constant, and is 3 msec in this embodiment. As a result, there is no change in the number of reversals, and the induction motor 78
The startup sound will be lower. In addition, by switching from AC square wave output by the inverter output circuit to commercial power supply (sine wave) at high torque rotation speed (full rotation), the operating noise at high torque is further reduced, and the commercial power supply (sine wave) The power factor is improved and the energy saving effect is significant due to low running costs.

In the above-mentioned embodiment, when the regulated voltage of the voltage regulating circuit 110 reaches the maximum, that is, at full rotation, the AC rectangular wave output by the inverter output circuit 111 is switched to the commercial power supply (sine wave). However, if the voltage of the commercial power supply is set and switched to an arbitrary voltage value according to the characteristics of each induction motor, the operating noise at the optimum value of high torque depending on the usage conditions can be further reduced.

[0016]

[Effects of the Invention] As described above, according to the present invention, a power supply switching circuit is provided which switches the voltage applied to the induction motor from the inverter output circuit to the commercial power supply when the regulated voltage of the voltage regulation circuit reaches the maximum. Therefore, it is possible to obtain a rotation speed control device for a blower motor that improves the power factor at high torque and minimizes running costs.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a rotation speed control device for a blower motor in an embodiment of the present invention.

FIG. 2 is an operation waveform diagram showing the operation of the rotation speed control device for the blower motor in FIG. 1;

FIG. 3 is a circuit showing a conventional rotation speed control device for a blower motor.

[Explanation of symbols]

78 Induction motor 110 Voltage adjustment circuit 111 Inverter output circuit 113 Diode bridge 116 Power switching relay 116C1 Auxiliary C contact 116C2 Auxiliary C contact 118 Power switching circuit

Claims (2)

[Claims] Claim 1: A single-phase or three-phase induction motor that rotationally drives a fan, a voltage adjustment circuit that receives a power supply voltage and adjusts the voltage by phase control, and a rectifier that converts the adjusted voltage into a DC voltage. and an inverter output circuit that converts the output of the rectifier circuit into alternating current and applies it to the induction motor. A rotation speed control device for a blower motor, characterized in that a power supply switching circuit is provided for switching the voltage applied to the induction motor from the inverter output circuit to the commercial power supply. 2. The rotation speed control device for a blower motor according to claim 1, wherein the power supply switching circuit is configured to be able to switch at an arbitrary voltage value depending on the characteristics of each induction motor.