KR880004035Y1 - Ac mortor - Google Patents

Abstract

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Description

Power saving and electronic braking device for three-phase induction motors

1 is a block diagram of a power saving and electronic braking apparatus of a three-phase induction motor according to the present invention.

FIG. 2 is a circuit diagram of a preferred embodiment of the present invention, in which FIG. 2 (a) is a circuit diagram of a power saving circuit section and FIG. 2 (b) is a circuit diagram of an electronic braking control circuit section.

* Explanation of symbols for main parts of the drawings

1: three-phase induction motor 2, 3, 4: bidirectional solid state AC switch means

10, 20, 30: phase control circuit 11, 21, 31: current detector

12, 22, 32: reference signal supply 13, 23, 33: adder

14, 24, 34: pulse generator 15, 25, 35: pulse amplifier

16, 26, 36: DC power supply 17: reference signal supply

40: electronic brake control circuit 41: braking command signal generator

42: brake switch driver 43: pulse generator

44: power cut off switch drive 45: current (轉 流)

CP11-CP12, CP21-CP24, CP31-CP34: Switching Means

CT1-CT3: Current transformer SW1: External input switch

SW2: Braking switch SW3: Reset switch

The present invention relates to a power saving and electronic braking device of a three-phase induction motor, and particularly, detects a current change of a three-phase induction motor according to a load change through a current transformer and controls the AC power supplied to the motor according to the detected information to save power. The present invention relates to a power saving and electronic braking apparatus for a three-phase induction motor capable of achieving an instant braking by a magnetic force formed by supplying a direct current to the motor when braking.

In general, induction motors are widely used as a power source of many industrial devices because they have no trouble and are inexpensive. However, an induction motor has a disadvantage that power is consumed by heat of the motor at no load or light load. A solution to this problem is described in US Patent No. 4,052,648 (POWER FACTOR CONTROL SYSTEM FOR AC INDUCTION MOTOR). There is a risk of burnout and a high manufacturing price.

In addition, the single-phase induction motor electronic starter type power saving device described in Korean Utility Model Registration Application No. 82-2094 should be used only for single-phase, and should use the limited and expensive ride generator that is applied only to the motor of the condenser start type. There was an inconvenience to equip the motor with a mechanical structure.

In addition, when a direct current is applied to the AC motor, the rotor of the AC motor has a strong braking characteristic. Known brake methods include magnetic switch method using magnetic switch, diode, and resistance, and electronic method of attaching the clutch to the electric motor shaft to remove the clutch using an electromagnet. It is economical and has disadvantages in terms of reliability and lifespan due to the contact point, and uses resistance in direct current control, so there is power loss.In the latter case, the trouble of wear and breakage due to the mechanical contact of the clutch when brake is applied There was a downside.

Therefore, an object of the present invention is to detect the current change of the three-phase induction motor according to the load change through the current transformer and to control the AC power supplied to the motor according to the detected information in order to solve the problems of the prior art as described above. The present invention provides a power saving and electronic braking device for a three-phase induction motor that is simple and can prevent starting failure and obtain excellent power saving effects.

Another object of the present invention is to provide a power saving and electronic braking apparatus for a three-phase induction motor capable of instantaneous braking of a motor by a magnetic force formed by supplying a direct current to a flow motor by using a power saving circuit during braking of the induction motor. have.

In order to achieve the above object, the present invention connects each phase output terminal (RST) of the three phase AC power source to each phase input terminal (UVW) of the three phase induction motor through a bidirectional solid state AC switch means. In controlling the power supply, each phase phase control circuit for controlling the conduction angle of the bidirectional solid state AC switch means in proportion to the current change according to the load change of the three-phase induction motor, and is input in accordance with the braking command signal The conduction angle of the contactless AC switch means for the R-phase control is controlled only at the + half wave of the R-phase voltage, and the conduction angle of the contactless AC switch means for the T-phase control is controlled only at the-half wave of the input T-phase voltage. Even if a direct current is supplied to the three-phase induction motor by controlling the conduction angle of the S-phase contactless AC switch means to cut off the S-phase voltage. And after a certain period of time, and the three-phase induction electronic braking control circuit and wherein the hayeoseo provided that the three-phase alternating-current power to the electric motor supplies a brake control signal to each phase the phase control circuit so that the full block.

When the present invention in more detail through the preferred embodiment of the present invention shown in the accompanying drawings as follows.

1 is a block diagram for explaining the overall function.

The R-phase output terminal of the three-phase AC power supply is connected to the U-phase input terminal of the three-phase induction motor 1 through bidirectional non-contacting AC switch means 2, for example, reversely connected thyristors SCR1 and SCR2. , S and T phase output terminals are two-phase induction motor switching means (3) (4), for example three-phase induction motors through anti-parallel connected thyristors (SCR3) and (SCR4), (SCR5) and (SCR6), respectively. Respectively connected to the V.W phase input terminal of (1), and between the two-way solid state AC switch means (2) (3) (4) and the UVW phase input terminal of the three-phase induction motor (1). (CT2) (CT3) is connected, and the detection current signals of the current transformers (CT1) (CT2) (CT3) are connected to be input to the respective phase control circuits (10), (20) and (30), respectively. The + and-trigger signals of the control circuits 10, 20 and 30 are obtained by the respective thyristors SCR1 and SCR2, SCR3 and S of the bidirectional solid state switch means (2) (3) (4). SCR4), ( It is connected to supply to each gate terminal of SCR5) and (SCR6), and in response to the braking command signal to the current of the counter electromotive force generated across the U and W phase input terminal of the three-phase induction motor (1), The electronic brake control circuit 40 is connected to the respective phase control circuits 10, 20, 30 so that the braking control signal is supplied.

First, as shown in FIG. 2 (a), the phase-phase control circuit converts the current change of each phase of the three-phase induction motor 1 through the current transformers CT1, CT2, and CT3 into a diode D1. (D2) (D3) and (D4) current detectors (11) (21) (31) for rectifying and outputting a voltage signal through resistor (R1), resistor (R2) and resistor (R3). An adder consisting of reference signal supplies 12, 23, 32 for supplying a pseudo firing firing voltage signal supplied by a resistor, and a resistor R4 and a capacitor C1 for adding a voltage signal of a current detector to the reference signal; (13) (23) (33) and the synthesized voltage signal of the adder are charged to the capacitor C2 through the resistor R7, and the voltage signal across the capacitor C2 is applied to the single junction transistor UJT1. Connect to supply to the emitter and connect the single junction transistor when the emitter voltage of the single junction transistor (UJT1) reaches the upper limit voltage (VP) of the emitter. When the UJTI turns on and the capacitor C2 is discharged through the resistor R10 and the emitter voltage decreases, the emitter becomes non-conducting and is turned off and the cycle is repeated to generate a trigger pulse. 14) (24) (34) and + trigger pulses and-trigger pulses through the pulse transformer (PTI) connected to the collector by receiving the trigger pulse train through the resistor (R13) to the base of the transistor (Q1), respectively. It is composed of pulse amplifiers 15, 25 and 35, respectively.

Each of the parts supplies a DC voltage signal supplied from the rectifier RC, which is synchronously rectified between the devices, to the capacitor C2 of the pulse generator 14 through the resistor R8, and the resistor R11 and the resistor ( R9) is supplied to the base of the single-junction transistor (JUTI) and the voltage signal constant voltage by the resistor (R11) and the resistor (R12) and the zener diode (D5) is the reference signal generator (12), the reverse flow prevention diode DC is supplied through the switch means CP31, CP32, CP33 from the DC power supply 16, 26, 36 connected to be supplied to the primary winding of the pulse transformer PTI through D6.

The pulse generator 14 of the R phase control circuit 10 has a synthesized voltage signal of the adder 13 through a switch means CP11, and a reference point during braking supplied by the resistors R5 and R6. A reference signal of a reference signal supply 17 for supplying a whistle voltage signal is connected to be selectively supplied, and the -trigger pulse is connected to be output through a switch means CP21,

The pulse amplifier 25 of the S phase phase control circuit 20 is connected to supply a trigger pulse of the pulse generator 24 through a switch means CP22, and the + trigger pulse of the phase control circuit 30 is switched. The output is connected via means CP23.

The electronic brake control circuit 40 according to the present invention has a brake command signal generator 41 which generates a brake command signal by the brake switch SW2 and the external input switch SW1 as shown in FIG. 2 (b). ), A brake switch driver 42 comprising two parallel connection relays RY1 and RY2 connected directly to a thyristor SCR7 supplied with the brake command signal to a gate input terminal as a trigger signal, and the brake The switch means CP12, which is turned on from the off state by driving the relay RY1 of the switch 42, is connected to both ends of the capacitor C24, and the capacitor C24 starts to be charged from the off operation. The pulse generator 43 generates a trigger pulse when the emitter voltage of the transistor UJT2 reaches the emitter upper limit voltage VP, and the trigger pulse of the pulse generator 43 is supplied to the gate terminal. Serially connected to the receiving thyristor (SCR8) The thyristor (SCR9) is reversely connected to the power cut-off switch driver 44 composed of the relay RY3 and the DC input terminal supplied during braking of the three-phase induction motor 1, that is, both U and W phase input terminals. A current means 45 connected to the switch means CP24 which is connected when the relay RY2 of the brake switch driver 42 is driven between the anode and the gate of the thyristor SCR9. It is a combination of the two.

Each part has a direct current output of a rectifier of synchronous rectification diodes (D27-D30) in R phase, a pulse generator (43) and a power-off switch via a reset switch (SW3). The control unit 44 and the brake switch driver 42 are supplied to the drive unit 44 and through the switch means CP34 which is turned off when the relay RT3 is driven when the direct current passing through the reset switch SW3 is turned on. Connect to supply.

The above-mentioned first switch means are switched by the relays RY1 (RY2) and relay RY3, and the switching configuration is configured as shown in Table 1 below.

[table]

The operation and effects of the present invention configured as described above are as follows.

First, when the power saving function is described, the phase control of the R phase in the state where the first switch means is switched as described in Table 1 above, and the die Lister SCR2 outputs the + half wave of the input R phase voltage. The Lister SCR1 conducts -half waves, respectively, and the output voltage of the Lister SCR1 varies according to the trigger pulses applied to the gates of the Disters SCR1 and SCR2.

In addition, the R phase voltage is rectified by the rectifier RC and converted into a reverse flow, and the reverse flow voltage is clamped to a constant voltage based on the resistors R11 and R12 and the constant voltage diode D5 to output a constant voltage.

Here, the constant voltage signal is used to generate a gate signal synchronized with the input R. In the current transformer CT1, the voltage induced on the secondary side in proportion to the passing current, that is, the load amount, is rectified by the diodes D1-D4 and charged in the capacitor C1 of the adder 13 via the variable resistor R1.

On the other hand, the constant voltage signal is divided by the resistors R2 and R3 of the reference signal supply 12 and overlaps the voltage charged in the capacitor C1.

Therefore, in the adder 13, the superimposed voltage signal is supplied to the pulse generator 14 through the power saving position of the switch means CP11, and in the pulse generator 14, the voltage signal supplied through the resistor R7 is the condenser C2. ) Is charged. The charged voltage is applied to the emitter of the single junction transistor (UJTI) and when the charged voltage gradually increases to reach the emitter upper limit voltage (VP) of the single junction transistor (UJTI), the single junction transistor (UJTI) turns on and at the same time The trigger pulse is generated at the base 2 terminal. The pulse is applied to the base of the transistor Q1 through the diode D10 and the resistor R13 and amplified, and the amplified signal is induced on the secondary side of the pulse transformer PT1 so that the + trigger signal is passed through the diode D8. To the gate of the Lister SCR2, the -trigger signal is applied to the gate of the thyristor SCR1 via the diode D9 and the switch means CP27.

The reference signal supplier 12 supplies the lowest voltage which is operated at no load of the motor as a reference signal, and thus the voltage signal of the current detector 11 is added to the reference signal and outputted from the adder 13, so that the motor is started at the start of the motor. Since the voltage signal of the current detector 11 which is higher than usual in the same phase is added to the reference signal by the starting current (more than three times the normal current), the output voltage of the adder 13 is increased, so that the capacitor of the pulse generator 14 is increased. Since the charging time of (C2) is shortened, a trischer pulse with an earlier phase is generated.

Therefore, since the firing angle from the zero point of the R phase voltage becomes smaller, the conduction angle of the die Lister (SCR1) (SCR2) becomes wider, and the output voltage rises to the voltage necessary for starting the motor and continues until the motor starts normally. Power is supplied to ensure reliable starting, eliminating the risk of starting failure. After the motor is started, the current flowing to the motor is also reduced and the current flowing to the current transformer CT1 is also reduced. Accordingly, the voltage induced on the secondary side of the current transformer CT1 is also lowered to generate a pulse out of phase as described above. As a result, the conduction angle of the thyristors SCR1 and SCT2 is narrowed, so that the output voltage decreases and power saving effect can be obtained.

Similarly, the change in the amount of change in the load and the change in the current amount flowing through the current transformer CT1 occurs and the change is detected.The conduction angle of the thyristors SCR1 and SCR2 is controlled to operate at the lowest voltage at which the motor can rotate. Will be imported.

Also in S phase and T phase, the conduction angle of the bidirectional solid-state AC switch means 3 and 4 is controlled by the same action.

Next, the braking timing will be described with reference to FIG. 3.

When the external input switch SW1, for example, the overload detection switch SW1 or the brake switch SW2, is turned on during the above-described power saving operation, the brake command signal is applied to the brake switch driver 42 through the resistor R24 or the resistor R25. Since it is triggered by being input to the gate of the thyristor SCR7, the relays RY1 and RY2 are driven to switch the switch means CP11-CP12 and CP21-CP24 to the initial braking state shown in Table 1 above.

Therefore, since the switch means CP11 of the phase control circuit 10 is switched to the braking position, the reference signal provided by the resistors R5 and R6 of the reference signal generator 17 during braking is pulse generator 14. Since the charging time of the condenser C2 is charged by the reference signal during braking, the trigger pulse with a delayed phase is output. The trigger pulse is applied to the gate of the thyristor SCR2 in the off state of the switch means CP21 via the pulse transformer PT1 of the pulse amplifier 15. Accordingly, the bidirectional solid state AC switch means 2 only controls the conduction angle of + half wave of the applied R phase voltage. At the same time, since the switch means CP22 of the phase control circuit 20 is turned off, the trigger pulse generated from the pulse generator 24 is blocked from being supplied to the pulse amplifier 25, so that the bidirectional solid state AC switch means 3 is blocked. And the switching means CP23 of the phase control circuit 30 is turned off, so that the output of the + trigger pulse is cut off, and only the-trigger pulse is applied to the gate of the thyristor SCR5 so that the bidirectional solid state AC switch means 4 ) Controls only the conduction angle of-half wave of the applied T-phase voltage.

The reference signal is set such that the + trigger pulse for the + half wave of the S phase voltage is delayed to the same phase as the-trigger pulse for the-half wave of the T phase voltage.

Therefore, the R-phase voltage + half-wave is the W-phase input terminal-distorter (SCR5) of the primary winding-induction motor (1) of the U-phase input terminal-flow motor (1) of the dyster (SCR2) -induction motor (1). Since the DC loop connected to the T phase full-half wave through is formed, the primary winding of the induction motor 1 is magnetized in a predetermined direction, thereby constraining the rotor by this magnetic force. Therefore, since the rotor is not continuously rotated by the inertia force when turning off the conventional system, rapid braking is possible.

In addition, in the present invention, since the direct current supplied to the direct current input terminal of the induction motor 1 is in fact a pulse wave, the energy accumulated in the primary winding of the induction motor 1 during the turn-off of the pulsation efficiently flows to a small power. The current means 45 was connected between the direct current input terminals so as to generate strong braking.

Since the switch means CP24 is turned on by the driving of the relay RT2, the current means 45 is supplied with a trigger signal to the gate of the die thruster SCR9, and the die thruster is supplied from the W phase input terminal of the induction motor 1. A loop is formed and applied to the U-phase input terminal via (SCR9), so that a strong braking effect can be obtained because it is applied to the primary winding in phase with the pulse current supplied to the counter electromotive force generated in the turn-off of the pulse current.

The braking force described above can be adjusted to be strong by changing the resistance R6 of the reference signal supplier 17 which supplies the reference point whistle signal during braking to control the conduction angle of the die Lister SCR2.

At the same time as the relay RY1 is driven, the switch means CP12 of the pulse generator 43 is turned off in the on state, so that a current is supplied to the capacitor C24 through the resistor 29 and charged. When the charged voltage is applied to the emitter of the single junction transistor (UJT2) and reaches the emitter upper limit voltage (VP), the single junction transistor (UJT2) is turned on to generate a trigger pulse at the second terminal of the power cutoff switch driver ( The relay RY3 is turned on so that the switch means CP31-CP34 are switched as in the power-off time column of Table 1 because it is applied to the gate of the thyristor SCR8. That is, the braking time described above is determined by the charging time of the capacitor C24.

Therefore, when the braking force is supplied to the induction motor 1 and reaches the emitter upper limit voltage VP during the charging time up to the emitter upper limit voltage VP of the single junction transistor UJT2 of the capacitor C24, the relay RY3 is reached. Is activated so that the switch means CP34 is turned off so that the relays RY1 and RY2 are turned off so that the switch means CP11-CP12 and CP21-CP24 are restored to the power saving position and the switch means CP31-CP33 are turned off. Since the supply of DC to the phase control circuits 10, 20 and 30 is cut off and the trigger pulse stops, the bidirectional solid state AC switch means 2, 3 and 4 are all cut off and the three-phase AC to the flow motor Supply of power is completely cut off.

Due to the self-holding characteristic of the thyristor SCR8 of the power cutoff switch driving section 44, the reset switch SW3 is kept in the on state until the power is turned off. Therefore, by pressing the reset switch SW3 once to turn off the die Lister SCR8, the switch means CP31 to CP33 are turned off, and the switch means CP34 is turned on to restore the system.

As described above, in the present invention, only the current transformer can be used to eliminate the starting failure during start-up and to obtain a power saving effect, which is very simple, so that the failure rate is low and the manufacturing cost can be provided at low cost.

In addition, it is possible to provide instantaneous rapid braking by supplying direct current to the induction motor during braking by using the contactless AC switch means used for power saving, so it is very compact and economical without any disadvantages of wear and damage due to mechanical contact of the conventional mechanical braking device. And reliable.

Claims (3)

Each phase output terminal (RS T) of the three-phase AC power source is connected to each phase input terminal (UV W) of the three-phase induction motor (1) through bidirectional solid state AC switch means (2), (3) and (4). In controlling the power supply of a three-phase induction motor, the conduction of the bidirectional solid state alternating current switch means (2) (3) (4) is proportional to the current change caused by the load variation of the three-phase induction motor (1). The conduction angle of the contactless alternating current switching means 2 is controlled only in accordance with the phase phase control circuits 10, 20 and 30 for controlling the angle and the + half wave of the input R phase voltage according to the braking command signal, The conduction angle of the contactless AC switch means 4 is controlled only at -half of the input T-phase voltage, and the conduction angle of the contactless AC switch means 3 is controlled to block the input S-phase voltage. Direct current is supplied to three-phase induction motor (1), and three-phase induction after a certain time And an electronic braking control circuit 40 for supplying a braking control signal to the phase control circuits 10, 20, and 30 so that the three-phase AC power supplied to the synchronization 1 is completely blocked. Power saving and electronic braking system for three-phase induction motors. The current detector (11) according to claim 1, wherein the phase control circuits (10), (20), (30) detect current changes in each phase of the three-phase induction motor (1) with a current transformer (CT1) (CT2) (CT3). (21) (31), a reference signal supplier (12) (22) (32) for supplying a reference firing angle signal, and an adder for combining the output signal of the current detector and the reference signal of the reference signal supply ( 13) (23) (33), pulse generators (14) (24) (34) for generating trigger pulses according to the synthesized output signal of the adder, and amplifying the trigger pulses of the pulse generator, Pulse amplifiers 15, 25, 35 for outputting the trigger pulses respectively, and DC power supplies 16, 26, 36 for supplying direct current through the switch means CP31, CP32, CP33 to the respective parts. And each of which is combined with each other, and the pulse generator 14 of the phase control circuit 10 has a combined output signal and a brake reference point of the adder 13 through a switch means CP11. The reference signal of the reference signal supplier 17 for generating the whistle signal is connected to be selectively supplied, and the -trigger pulse is connected to be output through the switch means CP21, and the pulse amplifier of the phase control circuit 20 ( 25 is connected to supply the trigger pulse of the pulse generator 24 through the switch means CP22, the + trigger pulse of the phase control circuit 30 is connected to be output through the switch means (CP23), the switch Number (CP11, CP21-CP23, CP31-CP33) is a power saving and electronic braking device of a three-phase induction motor, characterized in that switched by the electronic brake control circuit (40). The electronic brake chair circuit (40) according to any one of claims 1 to 4, wherein the electronic brake chair circuit (40) uses a brake command generator (41) for generating a brake command signal and switches (CP11, CP21-CP23) by the brake command signal. The braking switch driver 42 for switching, the pulse generator 43 for generating a delay trigger pulse by the braking control signal of the brake switch driver 42, and the switch means CP31-CP33 by the delay trigger pulse. Current means (45) connected between a power cutoff switch driver 44 for switching the power supply switch and a DC input terminal during braking of the three-phase induction motor 1 to be triggered by a brake control signal of the brake switch driver 42. And a power saving and electronic braking device for a three-phase induction motor.