Fan speed controller based on three-phase motor

Abstract

A fan speed regulator based on three-phase motor, which comprises a sampling circuit of motor terminal voltage, a comparison circuit for comparing the signal outputted by the sampling circuit with a set value, and a control circuit for controlling the conducting area of the bidirectional thyristor according to the control signal outputted by the comparison circuit. The sampling value of the prior art rectification filter sampling circuit only corresponds to the amplitude of the output voltage of the bidirectional thyristor and cannot reflect the conducting area of the bidirectional thyristor. When the amplitude of the output voltage of the bidirectional thyristor is equal to the amplitude of the commercial power, the sampling value has no feedback effect. The voltage signal collected by the sampling circuit is the average value of the output voltage of the bidirectional thyristor. When the average value is compared with the set value, the comparison result is reliable. The conducting area of the bidirectional thyristor is controlled by the comparison result, so that the terminal voltage of the motor can be kept near the set value and the wind speed of the fan can be stabilized. The wind speed of the fan can be conveniently adjusted by adjusting the potentiometer. The speed measuring generator is omitted, so that the manufacturing cost can be reduced.

Description

Technical Field

[0001] This invention relates to a speed regulator for a fan. Background Technology

[0002] The wind speed of a fan can be adjusted by changing the terminal voltage of the motor. There are two types of fan speed controllers: closed-loop control and open-loop control.

[0003] The closed-loop control type includes a tachogenerator, a comparator circuit, a thyristor trigger circuit, and a thyristor. Its principle is that the tachogenerator converts the fan speed into a voltage signal, and the comparator circuit compares the speed signal with a set value. When the speed signal is greater than the set value, the thyristor trigger circuit reduces the conduction angle of the thyristor, and the thyristor reduces the terminal voltage of the motor, thus reducing the speed of the motor (fan). Conversely, the same applies, keeping the fan speed near the set value.

[0004] This type of speed controller uses a tachogenerator, which has a high manufacturing cost.

[0005] Some methods use the motor terminal voltage as the feedback voltage signal, which is obtained through rectification and filtering. However, the drawback is that the feedback voltage signal can only reflect the change in the amplitude of the motor terminal voltage, and cannot reflect the change in the conduction area of ​​the thyristor, resulting in a large control error in the motor terminal voltage.

[0006] Open-loop control type, including thyristor trigger circuit and thyristor, this speed controller has low manufacturing cost, but poor speed regulation stability. When the mains voltage fluctuates, the wind speed will also fluctuate. In particular, when the mains voltage is low, the motor may stop rotating. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a fan speed controller based on a three-phase motor, which has stable speed regulation performance and the fan speed is not affected when the mains voltage fluctuates; the speed controller eliminates the need for a tachogenerator, which can reduce manufacturing costs.

[0008] The technical solution of the present invention is a fan speed controller based on a three-phase motor, which includes a sampling circuit for the motor terminal voltage, a comparison circuit for comparing the sampling signal output by the sampling circuit with a set value, and a control circuit for controlling the conduction area of ​​the bidirectional thyristor according to the control signal output by the comparison circuit. Its characteristic is that the sampling circuit includes a transformer B1, the primary coil of transformer B1 is connected in parallel with the a-phase winding of the motor, one end of the secondary coil of the transformer is connected to the cathode of diode D1, the anode of diode D1 is connected to the inverting input terminal of operational amplifier A1 through resistor R1, the inverting input terminal of operational amplifier A1 is connected to the output terminal of operational amplifier A1 through capacitor C1, electronic switch DK1 is connected in parallel with capacitor C1, the non-inverting input terminal of operational amplifier A1 is grounded, the other end of the secondary coil of the transformer is connected to the anode of diode D2, the cathode of diode D2 is connected to the base of transistor T1 through resistor R2, the emitter of transistor T1 is grounded, the collector of transistor T1 is connected to the power supply VDD through resistor R3, the collector of transistor T1 is connected to the control terminal of electronic switch DK1, the output terminal of operational amplifier A1 is connected to the anode of diode D3, and the cathode of diode D3 is grounded through electrolytic capacitor C2.

[0009] The beneficial effects are as follows: Existing rectifier and filter sampling circuits only sample values ​​corresponding to the amplitude of the bidirectional thyristor output voltage, failing to reflect the conduction region of the thyristor. When the amplitude of the bidirectional thyristor output voltage equals the amplitude of the mains voltage, the sampled value has no feedback effect. This sampling circuit collects the average value of the bidirectional thyristor output voltage. When compared with the set value, the comparison result is reliable. Using this comparison result to control the conduction region of the bidirectional thyristor ensures that the motor's terminal voltage remains near the set value. Stable motor terminal voltage leads to stable fan speed. The fan speed can be easily adjusted by adjusting the potentiometer. This speed controller eliminates the need for a tachogenerator, reducing manufacturing costs. Attached Figure Description

[0010] Figure 1 This is the circuit schematic diagram of the present invention.

[0011] Figure 2 for Figure 1 A circuit diagram of the control unit.

[0012] Figure 3 for Figure 1 Another circuit diagram of the control unit.

[0013] Figure 4 This is a wiring diagram of a bidirectional thyristor and a motor winding. Detailed Implementation

[0014] A fan speed controller based on a three-phase motor includes a sampling circuit for the motor terminal voltage, a comparison circuit for comparing the sampled signal output by the sampling circuit with a set value, and a control circuit for controlling the conduction zone of a bidirectional thyristor based on the control signal output by the comparison circuit.

[0015] The sampling circuit includes a transformer B1. The primary coil of transformer B1 is connected in parallel with the a-phase winding of the motor. One end of the secondary coil of transformer B1 is connected to the cathode of diode D1. The anode of diode D1 is connected to the inverting input of operational amplifier A1 through resistor R1. The inverting input of operational amplifier A1 is connected to the output of operational amplifier A1 through capacitor C1. Electronic switch DK1 is connected in parallel with capacitor C1. The non-inverting input of operational amplifier A1 is grounded. The other end of the secondary coil of the transformer is connected to the anode of diode D2. The cathode of diode D2 is connected to the base of transistor T1 through resistor R2. The emitter of transistor T1 is grounded. The collector of transistor T1 is connected to power supply VDD through resistor R3. The collector of transistor T1 is connected to the control terminal of electronic switch DK1. The output of operational amplifier A1 is connected to the anode of diode D3. The cathode of diode D3 is grounded through electrolytic capacitor C2.

[0016] The principle is that resistor R1, capacitor C1 and operational amplifier A1 form an integrating circuit. When the voltage polarity of the other end of the secondary coil is positive, the collector of transistor T1 is at a low level and electronic switch DK1 is cut off. At this time, the voltage polarity of one end of the secondary coil of transformer B1 is negative, diode D1 is turned on, and capacitor C1 is charged through resistor R1. When the voltage polarity at one end of the secondary coil changes from negative to 0, diode D1 is cut off, charging ends, and the voltage on capacitor C1 corresponds to the average value of the output voltage of the bidirectional thyristor. At this time, the voltage polarity at the other end of the secondary coil is also 0, the collector of transistor T1 is at a high level, electronic switch DK1 is turned on, and capacitor C1 is discharged. During charging, if the voltage across capacitor C1 is greater than the voltage across electrolytic capacitor C2, diode D3 conducts, and the voltage across electrolytic capacitor C2 rises along with the voltage across capacitor C1. If the voltage across capacitor C1 is less than the voltage across electrolytic capacitor C2, diode D3 is cut off, and the voltage across electrolytic capacitor C2 remains constant. To prevent the voltage across electrolytic capacitor C2 from remaining consistently high, a discharge resistor Rb is connected in parallel with diode D3. The resistance value of Rb can be determined experimentally, ensuring that the voltage across electrolytic capacitor C2 corresponds to the average value of the output voltage of the bidirectional thyristor.

[0017] It should be noted that the sampling value of a traditional rectifier filter circuit only corresponds to the amplitude of the output voltage of the bidirectional thyristor and cannot reflect the conduction region of the bidirectional thyristor. When the amplitude of the output voltage of the bidirectional thyristor is equal to the amplitude of the mains voltage, the conduction region of the bidirectional thyristor changes, but the sampling value does not change. In this case, the sampling value has no feedback effect.

[0018] The comparison can be a differential operational amplifier circuit composed of operational amplifiers, with the non-inverting input terminal of the operational amplifier connected to a set value, the inverting input terminal connected to an electrolytic capacitor C2, and the output terminal outputting the comparison result.

[0019] The comparison circuit can also be constructed using transistors. Its structure includes transistor T2, with the base of transistor T2 connected to the cathode of diode D3, the collector of transistor T2 connected to power supply VDD, the emitter of transistor T2 grounded through resistor R4, the emitter of transistor T2 connected to the emitter of transistor T3, the base of transistor T3 connected to the slider of potentiometer W1, one end of potentiometer W1 connected to power supply VDD through resistor R5, the other end of potentiometer W1 grounded through resistor R6, the collector of transistor T3 connected to power supply VDD through resistor R7, and the collector of transistor T3 outputs a control signal.

[0020] The principle of the comparator circuit is that the voltage across resistor R4 corresponds to the voltage across electrolytic capacitor C2, and the voltage on the slider of potentiometer W1 is the set voltage. When the mains voltage increases, the output voltage of the bidirectional thyristor also increases, the voltage across resistor R4 increases accordingly, and the collector voltage of transistor T3 decreases; conversely, when the output voltage of the bidirectional thyristor decreases, the voltage across resistor R4 decreases accordingly, and the collector voltage of transistor T3 increases. Adjusting potentiometer W1 can set the output voltage of the bidirectional thyristor.

[0021] The control circuit includes a first control unit CF1, a second control unit CF2, and a third control unit CF3. The first pin 1 and the second pin 2 of the first control unit CF1 are connected to the A phase and B phase of the mains power, respectively. The seventh pin 7 of the first control unit CF1 is connected to the collector of the transistor T3. The third pin 3 of the first control unit CF1 is connected to the power supply VDD. The sixth pin 6 of the first control unit CF1 is grounded. The fourth pin 4 of the first control unit CF1 is connected to the control electrode G1 of the first bidirectional thyristor SCR. The fifth pin 5 of the first control unit CF1 is connected to the cathode T11 of the first bidirectional thyristor SCR. The first pin 1 and the second pin 2 of the second control unit CF2 are connected to the B phase and C phase of the mains power, respectively. The seventh pin 7 of the second control unit CF2 is connected to the collector of the transistor T3. The third pin 3 of the second control unit CF2 is connected to the power supply VDD. The sixth pin 6 of the second control unit CF2 is grounded. The fourth pin 4 of the second control unit CF2 is connected to the control electrode G2 of the second bidirectional thyristor SCR2. The fifth pin 5 of the second control unit CF2 is connected to the cathode T12 of the second bidirectional thyristor SCR2. The first pin 1 and the second pin 2 of the third control unit CF3 are connected to the C phase and A phase of the mains power, respectively. The seventh pin 7 of the third control unit CF3 is connected to the collector of the transistor T3. The third pin 3 of the third control unit CF3 is connected to the power supply VDD. The sixth pin 6 of the third control unit CF3 is grounded. The fourth pin 4 of the third control unit CF3 is connected to the control electrode G3 of the third bidirectional thyristor SCR3. The fifth pin 5 of the third control unit CF3 is connected to the cathode T13 of the third bidirectional thyristor SCR3. The first control unit CF1, the second control unit CF2, and the third control unit CF3 have the same internal circuit structure. The first control unit CF1 includes a bridge rectifier QL1. The input terminals of the bridge rectifier QL1 correspond to the first pin 1 and the second pin 2. The first pin 1 and the second pin 2 are respectively connected to the A phase and B phase of the mains power. The positive terminal of the output terminal of the bridge rectifier QL1 is connected to the anode of the light-emitting diode of the optocoupler GE1. The cathode of the light-emitting diode is connected to the negative terminal of the output terminal of the bridge rectifier QL1 through the resistor R8. The collector of the phototransistor of the optocoupler GE1 is connected to the third pin 3. The third pin 3 is connected to the power supply VDD. The emitter of the phototransistor is connected to the emitter of transistor T4 through the resistor R9. The base of transistor T4 is connected to the seventh pin 7. The seventh pin 7 is connected to the external power supply T4. The collector of transistor T4 is connected to pin 6 via capacitor C4. Pin 6 is grounded. The collector of transistor T4 is connected to the emitter of unijunction transistor Q1. The second base of unijunction transistor Q1 is connected to pin 3. The first base of unijunction transistor Q1 is connected to pin 6 via the primary of pulse transformer M1. A freewheeling diode D5 is connected in parallel to the primary of pulse transformer M1. One end of the secondary of pulse transformer M1 is connected to pin 4. Pin 4 is externally connected to the control electrode G1 of the first bidirectional thyristor SCR1. The other end of the secondary of pulse transformer M1 is connected to pin 5. Pin 5 is externally connected to the cathode T11 of the first bidirectional thyristor SCR1.

[0022] The principle of this control unit is that when the mains power UAB is not zero, the optotransistor of optocoupler GE1 is turned on, providing a synchronization signal for the trigger pulse. When the base voltage of transistor T4 increases, the collector current of transistor T4 increases, the charging voltage of capacitor C4 increases, the unijunction transistor Q1 turns on earlier, and the pulse output of pulse transformer M1 triggers the bidirectional thyristor earlier, increasing the conduction area of ​​the bidirectional thyristor, and vice versa.

[0023] The first control unit CF1 can also have the following structure: it includes a transformer B2, the primary winding of which corresponds to the first pin 1 and the second pin 2. The first pin 1 and the second pin 2 are respectively connected to phase A and phase B of the AC mains. The secondary winding of the transformer B2 is connected to the input terminal of the bridge rectifier QL2. The negative terminal of the output terminal of the bridge rectifier QL2 is connected to the sixth pin 6, which is grounded. The positive terminal of the output terminal of the bridge rectifier QL2 is connected to the cathode of the Zener diode DW1 through a resistor R11. The anode of the Zener diode DW1 is connected to the sixth pin 6. The cathode of the Zener diode DW1 is connected to the emitter of the transistor T5 through a resistor R12. The base of the transistor T5 is connected to the seventh pin 7. Pin 7 is connected to the collector of transistor T4. The collector of transistor T5 is connected to pin 6 through capacitor C5. The collector of transistor T5 is connected to the emitter of unijunction transistor Q2. The second base of unijunction transistor Q2 is connected to pin 3. The first base of unijunction transistor Q2 is connected to pin 6 through the primary of pulse transformer M2. A freewheeling diode D5 is connected in parallel to the primary of pulse transformer M2. One end of the secondary of pulse transformer M1 is connected to pin 4. Pin 4 is connected to the control electrode G1 of the first bidirectional thyristor SCR1. The other end of the secondary of pulse transformer M1 is connected to pin 5. Pin 5 is connected to the cathode T11 of the first bidirectional thyristor SCR1.

[0024] The principle is that the mains power UAB is stepped down and rectified by transformer B2 and bridge rectifier QL2, and then regulated by Zener diode DW1 to form a synchronous signal power supply. When the base voltage of transistor T5 increases, the collector current of transistor T5 increases, the charging voltage of capacitor C5 increases, the unijunction transistor Q2 turns on earlier, and the pulse output of pulse transformer M2 triggers the bidirectional thyristor earlier, increasing the conduction area of ​​the bidirectional thyristor, and vice versa.

[0025] The MD winding of the motor is connected in a delta configuration. The first bidirectional thyristor SCR1 is connected in series in the a-phase winding circuit of the motor, the second bidirectional thyristor SCR2 is connected in series in the b-phase winding circuit of the motor, and the third bidirectional thyristor SCR3 is connected in series in the c-phase winding circuit of the motor.

Claims

1. A fan speed controller based on a three-phase motor, comprising a sampling circuit for the motor terminal voltage, a comparison circuit for comparing the sampling signal output by the sampling circuit with a set value, and a control circuit for controlling the conduction area of ​​a bidirectional thyristor based on the control signal output by the comparison circuit. Its characteristics are, The sampling circuit includes a transformer B1. The primary coil of transformer B1 is connected in parallel with the a-phase winding of the motor. One end of the secondary coil of the transformer is connected to the cathode of diode D1. The anode of diode D1 is connected to the inverting input of operational amplifier A1 through resistor R1. The inverting input of operational amplifier A1 is connected to the output of operational amplifier A1 through capacitor C1. Electronic switch DK1 is connected in parallel with capacitor C1. The non-inverting input of operational amplifier A1 is grounded. The other end of the secondary coil of the transformer is connected to the anode of diode D2. The cathode of diode D2 is connected to the base of transistor T1 through resistor R2. The emitter of transistor T1 is grounded. The collector of transistor T1 is connected to power supply VDD through resistor R3. The collector of transistor T1 is connected to the control terminal of electronic switch DK1. The output of operational amplifier A1 is connected to the anode of diode D3. The cathode of diode D3 is grounded through electrolytic capacitor C2.

2. The fan speed controller based on a three-phase motor according to claim 1, characterized in that, The comparison circuit includes transistor T2, with its base connected to the cathode of diode D3, its collector connected to power supply VDD, its emitter grounded through resistor R4, its emitter connected to the emitter of transistor T3, its base connected to the slider of potentiometer W1, one end of potentiometer W1 connected to power supply VDD through resistor R5, the other end of potentiometer W1 grounded through resistor R6, and its collector connected to power supply VDD through resistor R7. A control signal is output from the collector of transistor T3.

3. The fan speed controller based on a three-phase motor according to claim 2, characterized in that, The control circuit includes a first control unit CF1, a second control unit CF2, and a third control unit CF3. The first and second pins of the first control unit CF1 are connected to phase A and phase B of the mains power, respectively. The seventh pin of the first control unit CF1 is connected to the collector of transistor T3. The third pin of the first control unit CF1 is connected to the power supply VDD. The sixth pin of the first control unit CF1 is grounded. The fourth pin of the first control unit CF1 is connected to the control electrode G1 of the first bidirectional thyristor SCR. The fifth pin of the first control unit CF1 is connected to the cathode T11 of the first bidirectional thyristor SCR. The first and second pins of the second control unit CF2 are connected to the B phase and C phase of the mains power, respectively. The seventh pin of the second control unit CF2 is connected to the collector of the transistor T3. The third pin of the second control unit CF2 is connected to the power supply VDD. The sixth pin of the second control unit CF2 is grounded. The fourth pin of the second control unit CF2 is connected to the control electrode G2 of the second bidirectional thyristor SCR2. The fifth pin of the second control unit CF2 is connected to the cathode T12 of the second bidirectional thyristor SCR2. The first and second pins of the third control unit CF3 are connected to the C phase and A phase of the mains power, respectively. The seventh pin of the third control unit CF3 is connected to the collector of the transistor T3. The third pin of the third control unit CF3 is connected to the power supply VDD. The sixth pin of the third control unit CF3 is grounded. The fourth pin of the third control unit CF3 is connected to the control electrode G3 of the third bidirectional thyristor SCR3. The fifth pin of the third control unit CF3 is connected to the cathode T13 of the third bidirectional thyristor SCR3. The first control unit CF1, the second control unit CF2, and the third control unit CF3 have the same internal circuit structure. The first control unit CF1 includes a bridge rectifier QL1. The input terminals of the bridge rectifier QL1 correspond to the first and second pins, which are respectively connected to the A and B phases of the AC mains. The positive terminal of the output terminal of the bridge rectifier QL1 is connected to the anode of the LED of the optocoupler GE1. The cathode of the LED is connected to the negative terminal of the output terminal of the bridge rectifier QL1 through resistor R8. The collector of the phototransistor of the optocoupler GE1 is connected to the third pin, which is connected to the external power supply VDD. The emitter of the phototransistor is connected to the emitter of transistor T4 through resistor R9. The base of transistor T4 is connected to the seventh pin. The seventh pin is connected to the collector of transistor T3. The collector of transistor T4 is connected to the sixth pin through capacitor C4. The sixth pin is grounded. The collector of transistor T4 is connected to the emitter of unijunction transistor Q1. The second base of unijunction transistor Q1 is connected to the third pin. The first base of unijunction transistor Q1 is connected to the sixth pin through the primary of pulse transformer M1. One end of the secondary of pulse transformer M1 is connected to the fourth pin. The fourth pin is connected to the control electrode G1 of the first bidirectional thyristor SCR1. The other end of the secondary of pulse transformer M1 is connected to the fifth pin. The fifth pin is connected to the cathode T11 of the first bidirectional thyristor SCR1.

4. The fan speed controller based on a three-phase motor according to claim 3, characterized in that, The first control unit CF1 includes a transformer B2. The primary winding of transformer B2 corresponds to the first and second pins, which are respectively connected to phase A and phase B of the AC mains. The secondary winding of transformer B2 is connected to the input terminal of bridge rectifier QL2. The negative terminal of the output terminal of bridge rectifier QL2 is connected to the sixth pin, which is grounded. The positive terminal of the output terminal of bridge rectifier QL2 is connected to the cathode of Zener diode DW1 through resistor R11. The anode of Zener diode DW1 is connected to the sixth pin. The cathode of Zener diode DW1 is connected to the emitter of transistor T5 through resistor R12. The base of transistor T5 is connected to... Pin 7 is connected to the collector of transistor T4. The collector of transistor T5 is connected to pin 6 through capacitor C5. The collector of transistor T5 is connected to the emitter of unijunction transistor Q2. The second base of unijunction transistor Q2 is connected to pin 3. The first base of unijunction transistor Q2 is connected to pin 6 through the primary of pulse transformer M2. One end of the secondary of pulse transformer M1 is connected to pin 4. Pin 4 is connected to the control electrode G1 of the first bidirectional thyristor SCR1. The other end of the secondary of pulse transformer M1 is connected to pin 5. Pin 5 is connected to the cathode T11 of the first bidirectional thyristor SCR1.

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