Speed controller for a fan

Abstract

A speed regulator of a fan, which comprises a motor end voltage sampling circuit of the fan, a comparison circuit for comparing the voltage signal outputted by the sampling circuit with a set value, and a control circuit for adjusting the conducting area of the bidirectional thyristor according to the output signal of the comparison circuit; the sampling circuit converts the AC voltage outputted by the bidirectional thyristor into corresponding voltage average value, which has the beneficial effects that: 1. the voltage uc2 outputted by the sampling circuit corresponds to the voltage usr outputted by the bidirectional thyristor, that is, when the amplitude or / and the conducting area of usr changes, uc2 will change accordingly, while the conventional rectification filter circuit sometimes cannot reflect the change of the conducting area of the bidirectional thyristor; 2. the conducting area of the bidirectional thyristor is controlled according to the voltage uc2, so as to stabilize the voltage usr outputted by the bidirectional thyristor and the rotating speed of the fan, and avoid the stop rotating caused by the under-voltage of the commercial power; 3. the speed measuring generator is omitted, so as to reduce the manufacturing cost.

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, when the speed signal is less 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).

[0004] This type of speed controller uses a tachogenerator, which has a high manufacturing cost and is not conducive to market competition.

[0005] Open-loop control type, including thyristor trigger circuit and thyristor, 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 thyristor output voltage is low and the mains voltage is low, the motor may stop rotating. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a speed regulator for a wind turbine with stable speed regulation performance, which does not affect the speed of the wind turbine when the mains voltage fluctuates; the speed regulator eliminates the need for a tachogenerator, thereby reducing manufacturing costs.

[0007] The technical solution of the present invention is a speed regulator for a fan, which includes a motor terminal voltage sampling circuit for the fan, a comparison circuit for comparing the voltage signal output by the sampling circuit with a set value, and a control circuit for adjusting the conduction area of ​​the bidirectional thyristor according to the output signal of the comparison circuit. Its characteristic is that the sampling circuit includes a transformer B1, the primary winding of transformer B1 is connected in parallel with the stator coil XL of the motor, the secondary winding of the transformer is connected to the input terminal of bridge rectifier QL1, the output terminal of bridge rectifier QL1 is connected to the base of transistor T2, the emitter of transistor T2 is grounded through resistor R3, the collector of transistor T2 is connected to power supply VDD through resistor Rc, the collector of transistor T2 is connected to the base of transistor T3, and the emitter of transistor T3 is connected to power supply VDD through resistor R4. The power supply is VDD. The collector of transistor T3 is grounded through electrolytic capacitor C1. Electrolytic capacitor C1 is connected in parallel with electronic switch K1. The collector of transistor T3 is connected to the base of transistor T4. The collector of transistor T4 is connected to the power supply VDD. The emitter of transistor T4 is grounded through capacitor C2. The emitter of transistor T4 is connected to the non-inverting input of operational amplifier A1. The inverting input of operational amplifier A1 is connected to its output. The output of operational amplifier A1 is the output of the sampling circuit. The output terminal of the bridge rectifier QL1 is connected to the base of transistor T1 through resistor R1. The emitter of transistor T1 is grounded. The collector of transistor T1 is connected to the power supply VDD through resistor. The collector of transistor T1 is connected to the control terminal of electronic switch K1.

[0008] The comparator circuit includes a transistor T5. The base of transistor T5 is connected to the slider of potentiometer W1. One end of potentiometer W1 is connected to power supply VDD through resistor R5, and the other end of potentiometer W1 is grounded. The emitter of transistor T5 is connected to the output of operational amplifier A1. The collector of transistor T5 is connected to power supply VDD through resistor R6. The collector of transistor T5 is the output of the comparator circuit.

[0009] The control circuit includes comparator A2. The non-inverting input of comparator A2 is connected to the collector of transistor T5. The inverting input of comparator A2 is grounded through capacitor C3. Electronic switch K2 is connected in parallel with capacitor C3. The control electrode of electronic switch K2 is connected to the collector of transistor T1 through capacitor C4. The control electrode of electronic switch K2 is grounded through resistor R12. Diode D2 is connected in parallel with resistor R12. The anode of diode D2 is grounded. The output of comparator A2 is connected to the base of transistor T6 through resistor R10. The emitter of transistor T6 is connected to power supply VDD through resistor R9. The collector of transistor T6 is grounded through the primary winding of pulse transformer B2. One end of the secondary winding of pulse transformer B2 is connected to the control electrode of bidirectional thyristor SCR. The other end of the secondary winding of pulse transformer B2 is connected to one end of bidirectional thyristor SCR through resistor R11. The bidirectional thyristor SCR is connected in series with the stator coil of the motor.

[0010] Its beneficial effects are: 1. The output voltage uc2 of the sampling circuit corresponds to the output voltage usr of the bidirectional thyristor. That is, when the amplitude and / or conduction area of ​​usr changes, uc2 will change accordingly. However, conventional rectifier and filter circuits sometimes cannot reflect the changes in the conduction area of ​​the bidirectional thyristor; 2. By controlling the conduction area of ​​the thyristor according to the voltage uc2, the output voltage usr of the bidirectional thyristor is stabilized, thus stabilizing the speed of the fan and avoiding the shutdown caused by undervoltage of the mains power; 3. It eliminates the need for a tachogenerator, which can reduce manufacturing costs. Attached Figure Description

[0011] Figure 1 This is the circuit schematic diagram of the present invention.

[0012] Figure 2 The waveform diagram shows the relevant points in the sampling circuit. Detailed Implementation

[0013] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0014] A speed controller for a fan includes a motor terminal voltage sampling circuit, a comparison circuit that compares the voltage signal output by the sampling circuit with a set value, and a control circuit that adjusts the conduction area of ​​a bidirectional thyristor according to the output signal of the comparison circuit; the motor is a single-phase AC motor.

[0015] The sampling circuit includes a transformer B1. The primary winding of transformer B1 is connected in parallel with the stator coil XL of the motor. The secondary winding of the transformer is connected to the input terminal of a bridge rectifier QL1. The negative terminal of the output terminal of bridge rectifier QL1 is grounded, and its positive terminal is connected to the base of transistor T2. The emitter of transistor T2 is grounded through resistor R3. The collector of transistor T2 is connected to power supply VDD through resistor Rc. The collector of transistor T2 is connected to the base of transistor T3. The emitter of transistor T3 is connected to power supply VDD through resistor R4. The collector of transistor T3 is grounded through electrolytic capacitor C1. Resistor R12 is connected in parallel with electrolytic capacitor C1. Electronic switch K1 is connected in parallel with electrolytic capacitor C1. The collector of transistor T3 is connected to the base of transistor T4. The collector of transistor T4 is connected to power supply VDD. The emitter of transistor T4 is grounded through capacitor C2. The emitter of transistor T4 is connected to the non-inverting input of operational amplifier A1. The inverting input of operational amplifier A1 is connected to its output. The output of operational amplifier A1 is the output of the sampling circuit. The output terminal of the bridge rectifier QL1 is connected to the base of transistor T1 through resistor R1. The emitter of transistor T1 is grounded. The collector of transistor T1 is connected to the power supply VDD through resistor. The collector of transistor T1 is connected to the control terminal of electronic switch K1.

[0016] The sampling principle is that the voltage ud output by the bridge rectifier corresponds to the terminal voltage usr of the stator coil, and the collector current of transistor T3 changes with the voltage ud. When the voltage ud is greater than 0, the collector voltage uk of transistor T1 is low, the electronic switch K1 is off, the collector current of transistor T3 charges electrolytic capacitor C1, when the voltage uc1 of electrolytic capacitor C1 is greater than the voltage uc2 of capacitor C2, capacitor C2 is charged, and charging ends when the voltage ud is 0. When voltage ud is 0, voltage uk is high, electronic switch K1 is turned on, electrolytic capacitor C1 is discharged, voltage uc1 drops to 0, transistor T4 is turned off, and voltage uc2 of capacitor C2 does not decrease with voltage uc1. Operational amplifier A1 forms a voltage follower with power amplification function, and its output voltage value is equal to the value of uc2.

[0017] The technical effect of the sampling circuit is that its output voltage uc2 corresponds to the average value of the thyristor output voltage usr. That is, when the amplitude of usr and / or the conduction region changes, uc2 will change accordingly.

[0018] It should be noted that when the conduction angle of the bidirectional thyristor is in the range of 90 degrees to 180 degrees, a conventional rectifier and filter circuit can be used for sampling. However, when the conduction angle of the bidirectional thyristor is in the range of 0 to 90 degrees, the sampled voltage can only reflect the amplitude of the thyristor's output voltage, not the average value, that is, it cannot reflect the changes in the conduction area of ​​the bidirectional thyristor.

[0019] The comparison circuit can be a differential amplifier composed of operational amplifiers. The differential amplifier will subtract the voltage uc2 from the set value and output the difference. The comparator circuit can also be constructed using transistors and resistors. Its structure includes transistor T5, with the base of transistor T5 connected to the slider of potentiometer W1. One end of potentiometer W1 is connected to power supply VDD through resistor R5, and the other end of potentiometer W1 is grounded. The emitter of transistor T5 is connected to the output of operational amplifier A1, and the collector of transistor T5 is connected to power supply VDD through resistor R6. The collector of transistor T5 is the output of the comparator circuit.

[0020] Resistor R5 and potentiometer W1 constitute a setpoint generation circuit. Adjusting the potentiometer can change the output voltage of the bidirectional thyristor.

[0021] The control circuit can be a conventional unipolar transistor trigger circuit, whose output controls the conduction angle of the bidirectional thyristor. Alternatively, the control circuit can be constructed from an integrated circuit comparator, which includes comparator A2. The non-inverting input of comparator A2 is connected to the collector of transistor T5, and the inverting input of comparator A2 is grounded through capacitor C3. Electronic switch K2 is connected in parallel with capacitor C3. The control electrode of electronic switch K2 is connected to the collector of transistor T1 through capacitor C4, and the control electrode of electronic switch K2 is grounded through resistor R13. A diode D2 is connected in parallel with resistor R13, and the anode of diode D2 is grounded. The output of comparator A2 is connected to the base of transistor T6 through resistor R10. The emitter of transistor T6 is connected to power supply VDD through resistor R9. The collector of transistor T6 is grounded through the primary winding of pulse transformer B2. One end of the secondary winding of pulse transformer B2 is connected to the control terminal of bidirectional thyristor SCR. The other end of the secondary winding of pulse transformer B2 is connected to one end of bidirectional thyristor SCR through resistor R11. The bidirectional thyristor SCR is connected in series with the stator coil XL of the motor.

[0022] The control principle is as follows: the voltage at the inverting input of comparator A2 is equal to the voltage at capacitor C3. Power supply VDD charges capacitor C3 through resistor R8, causing the voltage at the inverting input of comparator A2 to gradually increase. When the voltage at the inverting input of comparator A2 is greater than the voltage at the non-inverting input of comparator A2, the output of comparator A2 becomes low, transistor T6 conducts, and the pulse transformer outputs a pulse to turn on the bidirectional thyristor. As the voltage at the non-inverting input of comparator A2 increases, the charging time of capacitor C3 also increases, and the conduction region of the bidirectional thyristor decreases. Conversely, as the voltage at the non-inverting input of comparator A2 decreases, the charging time of capacitor C3 also decreases, and the conduction region of the bidirectional thyristor increases. When voltage usr crosses zero, voltage uk1 is at a high level, the differentiating circuit outputs a pulse, and electronic switch K2 turns on to discharge capacitor C3; the differentiating circuit consists of capacitor C4 and resistor R12; When the mains voltage decreases, the output voltage usr of the bidirectional thyristor also decreases, correspondingly reducing the sampling voltage uc2 and the collector voltage of transistor T5. This means the voltage at the non-inverting input of comparator A2 decreases, the charging time of capacitor C3 decreases, the conduction region of the bidirectional thyristor increases, and the output voltage usr of the bidirectional thyristor increases. Conversely, when the mains voltage increases, the output voltage usr of the bidirectional thyristor also increases, correspondingly increasing the sampling voltage uc2 and the collector voltage of transistor T5. This means the voltage at the non-inverting input of comparator A2 increases, the charging time of capacitor C3 increases, the conduction region of the bidirectional thyristor decreases, and the output voltage usr of the bidirectional thyristor decreases. This stabilizes the motor terminal voltage and the fan speed.

Claims

1. A speed controller for a fan, comprising a sampling circuit for the motor terminal voltage of the fan, a comparison circuit for comparing the voltage signal output by the sampling circuit with a set value, and a control circuit for adjusting the conduction area of ​​the bidirectional thyristor according to the output signal of the comparison circuit. characterized in that The sampling circuit includes a transformer B1. The primary winding of transformer B1 is connected in parallel with the stator coil XL of the motor. The secondary winding of the transformer is connected to the input terminal of bridge rectifier QL1. The output terminal of bridge rectifier QL1 is connected to the base of transistor T2. The emitter of transistor T2 is grounded through resistor R3. The collector of transistor T2 is connected to power supply VDD through resistor Rc. The collector of transistor T2 is connected to the base of transistor T3. The emitter of transistor T3 is connected to power supply VDD through resistor R4. The collector of transistor T3 is grounded through electrolytic capacitor C1. Electrolytic capacitor C1 is connected in parallel with electronic switch K1. The collector of transistor T3 is connected to the base of transistor T4. The collector of transistor T4 is connected to power supply VDD. The emitter of transistor T4 is grounded through capacitor C2. The emitter of transistor T4 is connected to the non-inverting input terminal of operational amplifier A1. The inverting input terminal of operational amplifier A1 is connected to its output terminal. The output terminal of operational amplifier A1 is the output terminal of the sampling circuit. The output terminal of the bridge rectifier QL1 is connected to the base of transistor T1 through resistor R1. The emitter of transistor T1 is grounded. The collector of transistor T1 is connected to the power supply VDD through resistor. The collector of transistor T1 is connected to the control terminal of electronic switch K1.

2. The speed controller of a fan according to claim 1, wherein The comparator circuit includes a transistor T5. The base of transistor T5 is connected to the slider of potentiometer W1. One end of potentiometer W1 is connected to power supply VDD through resistor R5, and the other end of potentiometer W1 is grounded. The emitter of transistor T5 is connected to the output of operational amplifier A1. The collector of transistor T5 is connected to power supply VDD through resistor R6. The collector of transistor T5 is the output of the comparator circuit.

3. The speed controller of the fan according to claim 2, characterized in that, The control circuit includes comparator A2. The non-inverting input of comparator A2 is connected to the collector of transistor T5. The inverting input of comparator A2 is grounded through capacitor C3. Electronic switch K2 is connected in parallel with capacitor C3. The control electrode of electronic switch K2 is connected to the collector of transistor T1 through capacitor C4. The control electrode of electronic switch K2 is grounded through resistor R13. Diode D2 is connected in parallel with resistor R12. The anode of diode D2 is grounded. The output of comparator A2 is connected to the base of transistor T6 through resistor R10. The emitter of transistor T6 is connected to power supply VDD through resistor R9. The collector of transistor T6 is grounded through the primary winding of pulse transformer B2. One end of the secondary winding of pulse transformer B2 is connected to the control electrode of bidirectional thyristor SCR. The other end of the secondary winding of pulse transformer B2 is connected to one end of bidirectional thyristor SCR through resistor R11. The bidirectional thyristor SCR is connected in series with the stator coil XL of the motor.

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