GB2336495A

GB2336495A - Harmonic current filters for single-phase triac switching circuits

Info

Publication number: GB2336495A
Application number: GB9913046A
Authority: GB
Inventors: Eung-Gu Kim; Jin-Gon Kwon; Bu-Hyeon Kim; Gie-Yong Lee
Original assignee: Samsung Gwangju Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1997-01-30
Filing date: 1998-01-26
Publication date: 1999-10-20
Anticipated expiration: 2018-01-26
Also published as: GB2336496A; GB9913048D0; GB9913046D0; GB2336496B; GB2336495B

Abstract

RL filters 178,180 are inserted in the supply conductors to reduce the level of harmonic currents flowing into the supply 172. The RL filters comprise a coil L51,L52 wound around a core in parallel with a resistor R51,R52.

Description

1 2336495 CIRCUIT FOR ATTENUATING HARMONIC WAVE CURRENTS The present

invention relates to a circuit for attenuating harmonic wave currents. More particularly, the present invention relates to a circuit, which s controls switching of AC power utilizing a triac, for attenuating harmonic wave currents generated in a load.

Harmonic wave currents are generated in all loads using AC power from electric home appliance to industrial machinery. However, harmonic wave lo currents cause AC power to fluctuate, shortening the life span of the electric product. Further, the prior art circuit using a triac for controlling the switching of AC power does not effectively attenuate harmonic wave currents, thereby making the development of high-quality electric products difficult.

is In particular, it is common for wave forms of current, which are used in electric home appliance, to include harmonic wave currents. This problem is compounded as more electric appliances are used in an electric power system. Accordingly, serious interruptions occur in the power system.

The prior art control circuit using a triac for switching AC power will be described hereinafter.

Triac is an abbreviation for Triode AC Switch which is a bi-directional thyristor which can be used in an AC circuit. Since the triac is an electronic device which is able to be turned on in both directions, i.e. the positive and negative directions of the AC power source, by a positive or negative gate signal, the triac is applied to control AC power which uses common frequencies.

AC power has two zero voltage points for every cycle. Therefore, if the 30 triac is turned on once, it automatically turns off by itself at approximately zero voltage points. Accordingly, in the AC control circuit, even if the triac is not forcefully turned off, as in the DC circuit, the triac and the AC circuit turn off automatically in a state where a new turn on operation is not initiated. However, to maintain the off state of the AC circuit, trigger voltage must be inputted into the s circuit every half cycle of the AC power.

Further, since the triac is a semiconductor device, loss by a drop in voltage is unavoidable in an on state. However, since the triac can be bidirectionally turned on by small amounts of gate current, the triac is widely used as a device for lo controlling common use frequency AC power in vacuum cleaners, washing machines, refrigerators, microwave ovens, electric tools, small motors, and various other electric products used in the home, office and for industrial purposes.

In addition, with the development of the electronics industry, the triac is increasingly being used as the main AC power switching device in products such as microcomputers and VI-SPs. Following this trend has been the expansion of restrictions limiting the presence of harmonic wave currents in electronics products. A case in point has been the European Union's regulation of second to fortieth harmonic waves enacted on January 1, 1996.

Although other devices exist that reduce the generation of harmonic wave currents in AC circuits, triacs continue to be widely used as they have a clear price advantage over these other devices.

For the various reasons mentioned above, technology enabling the attenuation of harmonic wave currents has become a very important issue in the electrical and electronics fields.

Referring to Figure 1, shown is a schematic diagram of a conventional control circuit using a triac for switching AC power. In the drawing, the prior art

3 - AC control circuit using the triac comprises an AC power source 102, a load 104 driven by the AC power source 102, and a triac 106 bidirectionally turned on/off by gate input signals to control the switching of the AC power source 102.

The operation of the prior art AC power source control circuit structured as in the above will now be described.

If power is inputted into the control circuit to drive the load 104 by AC power source 102, the triac 106 is repeatedly turned on and off by a gate signal.

lo So, for example, an AC control circuit which drives a motor is turned on/off by the gate signal of the triac: 106. Here, if a gate signal is inputted into the gate of the triac 106 current is supplied to the load 104 by turning on the triac: 106 and the motor is driven. Further, when the motor is driven, harmonic wave currents are generated by mutual inductance and reverse electromotive force (e.m.f.) of the motor.

Referring now to Figures 2A-21), shown are voltage and current waveform graphs used for describing the operation of the prior art control circuit. Namely, Figure 2A is a waveform graph of AC power source voltage applied to the AC control circuit shown in Figure 1. Figure 213 is a waveform graph of gate current inputted to the gate of the triac 106, Figure 2C is a waveform graph of load current flowing into the load 104, and Figure 2D is a waveform graph of voltage applied to the triac 106 between points T2 and T1 of Figure 1.

The gate signal of the triac 106 enables the load current to be repeatedly turned on and off by the waveform of the AC voltage.

However, in Figure 1, when the motor (i.e. the load 104) is dniven, harmonic wave currents are generated as described above. Particularly, if it is a 30 150OW and above motor, the level of harmonic wave currents generated from the 4 motor surpasses the acceptable level set by IEC (International Electrotechnical Commission) regulations. The triac 106 can freely adjust the current by the gate current. However, if the triac 106 is turned on at the phase of approximately 90 degrees, current to a maximum value abruptly flows to the load 104 such that a maximum level of harmonic wave currents is generated.

Referring to Figures 3 and 4, shown respectively are a table of harmonic wave current test data derived from measuring the circuit of Figure 1, and a graph illustrating input voltage and load current according to the test data of Figure 3. In lo the following Table 1, shown are Class A harmonic wave current restriction values according to IEC regulations. That is, Table 1 illustrates maximum allowable current from the second harmonic wave to the fortieth harmonic wave according to IEC regulations.

- 5 <Table 1 >

DEGREE OF HARMONIC WAVE(n) MAXIMUM ALLOWABLE CURRENT(A) ODD NUMBER HARMONIC WAVES 3 2.30 A 1.14A 7 0.77 A 9 0.40 A 11 0.33 A 13 0.21 A 15<n<39 0. 15 x (1 5/n) EVEN NUMBER HARMONIC WAVES 2 1.08 A 4 0.43 A 6 0.30 A 8<n<40 0.23 X (8/n) As stated above, Figure 3 is a table of harmonic wave current test data derived from measuring the AC control circuit of Figure 1, i.e. data and comparative results monitored by a harmonic wave analyzer appear in this table. In Figure 3, "H Number" refers to the degree of the harmonic wave, and 9EC LimiC refers to the maximum permissible current allowed by IEC regulations, "Magnitude" refers to the measured size of the harmonic wave current, and a "PASS"P'FAW' indication refers to whether the measured value falls within the lo maximum permissible current level.

6 Also appearing in Figure 3 is "CH V, indicating the channel in which the test control circuit was monitored, "Steady State Harmonics TesC referring to the fact that the harmonic wave test was conducted in a steady state, and the date and time the test was conducted. Wolts" is the input voltage at which the test was performed, while "Amps" is the input current. Appearing under the table is the indication of "Failed Steady State Harmonics TesC meaning that IEC regulations were not met only when "FAIL" is indicated. Accordingly, only the third and fifth harmonic wave did not satisfy IEC regulations in the test.

In Figure 4, shown are waveforms of input voltage and load current according to the test data of Figure 3. Load current in the drawing is derived by adding the input current with the harmonic wave currents of Figure 3. The reference to "Class W in Figure 4 indicates output for equipment using electric is power having a specified input current waveform.

A system which controls the switching of AC power source utilizing the prior art triac is often used to control motor speed, and the phase of AC power is controlled by repeatedly turning the triac on and off.

Generally, a R-C (resistor-capacitor) or R-L (resistor-inductor) resonant circuit can be used to control the phase of harmonic waves. However, these circuits can remove only the fixed harmonic waves, and the resonant circuits effect other harmonic waves if the phase of the resonant circuit is not matched with the 25 phase of the harmonic wave. Accordingly, the use of these circuits is difficult.

Because the prior art insufficiently attenuates harmonic waves, the actual application to electric and electronic products is ineffectual.

7 It is an object of the present invention to provide a circuit for attenuating harmonic wave currents which uses a triac to attenuate harmonic wave currents generated when controlling phase of a motor, or load, in a circuit that controls switching of AC power, thereby stabilizing AC power and extending the life span of motors.

According to one aspect of the present invention, in a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising:

an AC power source; a load driven by the AC power source; a triac controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents in the power supply experienced by the load; wherein the means for attenuating harmonic wave currents includes a first filter connected to one end of the AC power source and a second filter connected to another end of the AC power source; and wherein the first filter includes a first core, a first coil wound around the first core, and a first resistor connected parallel to the first coil; and the second filter includes a second core, a second coil wound around the second core, and a second resistor connected parallel to the second coil.

According to another aspect of the present invention, in a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising:

an AC power source; a load driven by the AC power source; 8 - a triac controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents, in the power supply experienced by the load; wherein the means for attenuating harmonic wave currents includes a first filter connected to one end of the AC power source and a second filter connected to another end of the AC power source; and wherein the first filter includes a first core, and first and second coils wound around the first core and stacked one on top of the other; and the second filter includes a second core, and third and fourth coils wound around the second core and stacked one on top of the other.

Also, the first and third coils may be wound toward the load from the AC power source by the right hand rule, and the second and fourth coils may be 15 wound toward the AC power source from the load by the right hand rule.

According to a further aspect of the present invention, in a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising: an AC power source; a load driven by the AC power source; a triac controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents in the power supply experienced by the load; wherein the means for attenuating the harmonic wave currents includes a filter connected to opposing ends of the AC power source; and 9 the filter includes a core, a first coil connected between the AC power source and the load, and a second coil connected between the AC power source and the triac, and wherein the first coil is wound around the core toward the load from the AC power source by the right hand rule; the second coil is wound around the core towards the AC power source from the load by the right hand rule; and one terminal of the first coil, at which point the winding of the first coil begins, is connected to the load, while another terminal of the first coil, at which lo point the winding of the first coil ends, is connected to the AC power source.

According to a still further aspect of the present invention, in a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising: an AC power source; a load driven by the AC power source; a triac controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents, in the power supply experienced by the load; wherein the means for attenuating the harmonic wave currents includes a filter, the filter being connected between the AC power source and the load and wherein the filter includes a core, and first and second coils wound around the core and stacked one on top of the other.

According to another aspect of the present invention, the control circuit for switching the AC power may include a filter. The filter may include a core, and first and second coils wound around the core and stacked one on top of the other.

By way of example, specific embodiments of the invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a schematic diagram of a conventional control circuit using a s triac: for switching AC power; Figure 2A is a waveform graph of AC power source voltage applied to the AC control circuit shown in Figure 1; Figure 2B is a waveform graph of gate current inputted to a gate of a triac shown in Figure 1; Figure 2C is a waveform graph of load current flowing into a load shown in Figure 1; is Figure 2D is a waveform graph of voltage applied to a triac between points T2 and T 1 shown in Figure 1; Figure 3 is a table of harmonic wave current test data derived from 20 measuring the circuit of Figure 1; Figure 4 is a graph illustrating input voltage and load current according to the test data of Figure 3; Figure 5 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a first embodiment of the present invention; Figure 6 is a table of harmonic wave current test data derived from measuring the circuit of Figure 5; 11 Figure 7 is a graph illustrating load current according to the test data of the Figure 6; Figure 8 is a schematic diagram of a circuit for attenuating harmonic wave 5 currents in accordance with a second embodiment of the present invention; Figure 9 is a table of harmonic wave current test data derived from measuring the circuit of the Figure 6; Figure 10 is a graph illustrating load current according to the test data of the Figure 9; Figure 11 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a third embodiment of the present invention; is Figure 12 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a fourth embodiment of the present invention; Figure 13 is a table of harmonic wave current test data derived from 20 measuring the circuit of the Figure 12; Figure 14 is a graph illustrating load current according to the test data of the Figure 13; Figure 15 is a block diagram of a testing system for measuring the second to fortieth harmonic wave currents generated from a load of a circuit for controlling the switching of AC power.

Figure 16 is a schematic diagram of a circuit for attenuating harmonic wave 30 currents in accordance with a fifth embodiment of the present invention; 12 Figure 17 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a sixth embodiment of the present invention; Figure 18 is a table of harmonic wave current test data derived from measuring the circuit of the Figure 17; Figure 19 is a graph illustrating load current according to the test data of the Figure 18; Figure 20 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a seventh embodiment of the present invention; Figure 21 is a schematic diagram of a circuit for attenuating harmonic wave 15currents in accordance with an eighth embodiment of the present invention; Figure 22 is a schematic diagram of a circuit for attenuating harmonic wave current in accordance with a ninth embodiment of the present invention; Figure 23 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a tenth embodiment of the present invention; Figure 24 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with an eleventh embodiment of the present invention; Figure 25 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a twelfth embodiment of the present invention; and Figure 26 is a table of test data comparing various embodiments of the 30 present invention with the prior art.

- 13 Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

Referring first to Figure 5, shown is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a first embodiment of the present invention. The inventive circuit comprises an AC power source 112, a load 114 driven by the AC power source 112, a triac 116 for controlling switching of AC power by a gate signal, and means for attenuating harmonic wave currents, elements of the means being connected to opposing sides of the AC power source 112.

The above means for attenuating harmonic wave currents includes a first filter 118 and a second filter 120. The first filter 118 includes a first coil L 11 and a second coil L 12 wound around a first core (not shown) and stacked one on top of the other, and the second filter 120 includes a third coil L 13 and a fourth coil L 14 wound around a second core (not shown) and stacked one on top of the other.

Although R-C or L-C resonant circuits are generally used to control phase of harmonic wave currents, these circuits are difficult to use in real applications as they influence other harmonic wave currents if their phase does not match that of fixed harmonic wave currents. Therefore, the circuit of the present invention is constructed using iron coils and cores. The use of iron for these elements is done to take advantage of the low-frequency band characteristics this 25 material has such that a phase difference of harmonic wave currents induced in the coils L 11, L 12, L 13, and L 14 to each harmonic wave current is 180 degrees.

The AC circuit has a phase difference between an input and an output because of reactance elements existing in an impedance. The present invention adjusts the impedance of the circuit using the coils L 11, L 12, L 13, and L 14 such 14 that an output primary wave can have a 30-degree phase shift. Here, the phase shift includes 1) a phase shift of a primary wave, 2) a phase shift of the harmonic wave, 3) a phase shift of a relative primary wave. That is, the phase shift of the primary wave is 30 degrees by adjusting the impedance of the AC circuit, and the phase shift of each harmonic wave multiplies the phase shift of the primary wave by a degree of the harmonic wave.

Accordingly, if the phase shift of the primary wave is 30 degrees, the phase shift of fifth harmonic wave is 150 degrees, and if 30 degrees of the phase shift of lo the primary wave is further added to the fifth harmonic wave, a phase sequence becomes in the opposite direction of the phase shift of the primary wave. This phase shift is a relative phase shift. As a result, since a phase difference between one coil and another coil corresponding to each other is 180 degrees in the fifth harmonic wave, bi-directional currents are offset by the opposing directional forces. These phase shifts of the harmonic waves are performed by the coils.

The phase shifts of other degrees of harmonic waves are as shown in Table 2.

[Table 2]

Degree of Sequence of Relative Phase Shift Total Harmonic Phase Shift Phase Shift of Harmonic Wave Wave 30 150 180 7 + 30 210 180 9 30 330 360 11 + 30 390 360 - 15 Therefore, in the inventive circuit for controlling switching of AC power using the triac 116, the phase of each harmonic wave is adjusted to a multiple of degrees using the coils L 11, L 12, L 13, and L 14 made of material having good frequency characteristics in low frequency bands, thereby attenuating the harmonic wave currents generated from the load 114.

For example, in the case of the fifth harmonic wave, if the first and second coils L 11 and L 12 are wound a different number of times, the current flowing therethrough comes to be different. Namely, with the phase shift of the primary wave being 30 degrees, and the phase of the first and second coils L 11 and L 12 being adjusted 150 degrees by harmonic wave phase shift, a phase difference of degrees can be adjusted between the first coil LI 1 and the second coil L12.

Thus, the total harmonic wave current of the circuit is attenuated through the offsetting of the harmonic wave currents as in the above.

Through the above test, the phase of the harmonic wave current can be controlled by inductance of the coils L 11, L 12, L 13, and L 14, and the kind and capacity of the load 114. Also, the phase of the harmonic wave current can be varied by the winding direction of the coils L 11, L 12, L 13, and L 14.

In practice, when the first and third coils L 11 and L 13 are wound in the direction toward the load 114 from the AC power source 112 by the right hand rule, while the second and fourth coils L 12 and L 14 are wound in the direction toward the AC power source 112 from an output side of the load 114 also by the right hand rule, the greater effects of attenuating the harmonic wave currents is realised. The same effects can be achieved by winding the coils L 11, L 12, L 13 and L 14 in the reverse as in the above: winding the first and third coils L 11 and L 13 in the direction toward the AC power source 112 from the load 114 by the right hand rule, and winding the second and fourth coils L12 and L14 in the - 16 direction toward the load 114 from the AC power source 112 by the right hand rule.

Taking an example from the first embodiment, Figure 5 schematically illustrates a circuit for controlling switching of AC power for attenuating harmonic wave currents driving a 1500-watt motor. In the circuit, the first filter 118 and the second filter 120 are connected to opposing ends of the AC power source 112. The first and second coils L 11 and L 12 of the first filter 118 have different phases from each other, and the third and fourth coils L 13 and L 14 of the second filter 120 have different phases from each other.

Generally, the impedance of coils varies in accordance with the voltage and frequency of the power applied thereto, and by copper loss impedance generated in the coil. Accordingly, with different levels of current flowing to the first and second coils L 11 and L 12, and to the third and fourth coils L 13 and L 14, the primary wave can be passed through the filters 118 and 120 without being attenuated, while other harmonic waves are attenuated.

A detailed description of the circuit for attenuating harmonic wave currents according to various embodiments of the present invention will now be given with reference to the drawings.

First Embodiment Referring to Figures 5, 6 and 7 shown respectively are a schematic diagram of circuit for attenuating harmonic wave currents in accordance with a first embodiment of the present invention, a table of harmonic wave current test data derived from measuring the circuit of the Figure 5, and a graph illustrating load current according to the test data of the Figure 6.

17 - As shown in Figure 5, the inventive circuit according to the first embodiment comprises the AC power source 112, the load 114 driven by the AC power source 112, the triac 116 for controlling switching of AC power by a gate signal, and means for attenuating harmonic wave currents, elements of the means s being connected to opposing sides of the AC power source 112.

The above means for attenuating harmonic wave currents includes the first filter 118 and the second filter 120. The first filter 118 includes the first coil L 11 and the second coil L 12 wound around a first core (not shown) and stacked one on top of the other, and the second filter 1230 includes the third coil L 13 and the fourth coil L 14 wound around the second core (not shown) and stacked one on top of the other. The first and second coils L 11 and L 12, and the third and fourth coils L13 and L14 are connected parallel to each other. Also, an insulating layer (not shown) is inserted between the first and second coils L 11 and L 12, and between is the third and fourth coils L 13 and L 14 so that the coils are insulated from each other.

The first filter 118 is connected between the AC power source 112 and the load 114, and the second filter 120 is connected between the AC power source 112 and the triac 116.

Also, the first and third coils L 11 and L 13 are wound toward the load 114 from the AC power source 1.12 by the right hand rule, and the second and fourth coils L 12 and L 14 are wound toward the AC power source 112 from the load 114 by the right hand rule such that the effects of attenuating the harmonic wave currents are enhanced. Such winding directions were determined through testing.

The load used in the above circuit, and electrical capacities and characteristics of each coil are as follows.

18 An output of the motor is 1400 watts, and inductance of the first, second, third and fourth coils L 11, L 12, L 13, and L 14 are respectively 1. 450m11, 4.90mfl, 1.7 1 mH and 6.24m11. Also a quality factor of each coil L 11, L 12, L 13, and L 14 is Q 1, 4.3, Q2 5.8, Q3 6.2, Q4 6.2, respectively, and a resistance of each coil L 11, L12, L13 and L14 is LRI 2.20ohm, LR2 5.5ohm, LR3 2.89ohm, LR4 6.6ohm, respectively. Finally, a distortion factor of each coil L 11, L 12, L 13 and L 14 is LD 10.242, LD2 0.177, LD3 0.161, LD4 0.161, respectively.

Out of the above values, the lower the distortion factor the better, while the lo higher the value for the quality factor the better. It is best for the resistance for the coils LI I, L12, L13 and L14 to be small as possible, and differences in the inductances of the coils L 11, L 12, L 13, L 14 arise depending on the characteristics of the material used for each coil and core.

The inductance values, quality factor, resistance, and distortion factor for each coil L11, L12, L13, L14 are measured using an AF-4305 LCR Meter manufactured by Ando Company of Japan, under the conditions where n-ns (root mean square) voltage is 1 volt and the frequency is I KHz.

The test data measuring harmonic wave currents of Figure 6 is obtained from the above conditions. Further, the test data indicates that the circuit according to the first embodiment meets IEC regulations, and attains effects of attenuating harmonic wave currents that are 50% better than that of the prior art circuit for controlling switching of AC power of Figure 1.

Second Embodiment Referring to Figures 8, 9 and 10, shown respectively are a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a 30 second embodiment of the present invention, a table of harmonic wave current test 19 data derived from measuring the circuit of the Figure 6, and a graph illustrating load current according to the test data of the Figure 9.

As shown in Figure 8, the second embodiment is identical to the first embodiment except for the structure of first and second filters 128 and 130.

However, the connection of the filters 128 and 130 to the AC power source 122 is the same as in the first embodiment. That is, the first and second filters 128 and of the circuit for attenuating harmonic wave currents of the second embodiment are connected to opposing ends of the AC power source 112.

The first filter 128 includes a first core (not shown) and a first coil1, and the second filter 130 includes a second core (not shown) and a second coil L22. Also, the first filter 128, as in the first embodiment, is connected between the AC power source 112 and the load 114, while the second filter 130 is connected between the AC power source 112 and the triac 116.

The first coil L21 is wound toward the load 114 from the AC power source 112 by the right hand rule, while the second coil L22 is wound toward the AC power source 112 from the load 114 by the right hand rule such that the effects attenuating the harmonic wave currents are enhanced.

Test data appearing in Figure 9 is obtained from the circuit for attenuating harmonic wave currents according to the second embodiment. As shown by the data, the measured results of the second embodiment indicate that IEC regulations 25 are met.

- 20 Third Embodiment Figure 11 Is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a third embodiment of the present invention. The third embodiment is identical to the first embodiment except for the structure of first and second filters 138 and 140.

Namely, the first filter 138 includes a first core (not shown), and first, second, and third coils L31, L32, L33 connected parallel to each other; and the second filter 140 includes a second core (not shown), and fourth, fifth, and sixth coils L34, L35, L36 connected parallel to each other. The first filter 138 is connected between the AC power source 112 and the load 114, and the second filter 140 is connected between the AC power source 112 and the triac 116.

In the third embodiment, the first, second and third coils L3 1, L32, and L33 are wound toward the load 114 from the AC power source 112 by the right hand rule, while the fourth, fifth and sixth coils L34, L35, L36 are wound toward the AC power source 112 from the load 114 by the right hand rule such that the effects of attenuating the harmonic wave currents are enhanced.

Fourth Embodiment Figure 12 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a fourth embodiment of the present invention. The fourth embodiment is identical to the first embodiment except for the structure of first and second filters 148 and 150.

Namely, the first filter 148 comprises first and second coils L41 and L42, connected parallel to each other, and a first resistor R41 connected parallel to the first and second coils L41 and L42. Further, the second filter 150 comprises third 21 and fourth coils L43 and L44, connected parallel to each other, and a second resistor R42, connected parallel to the third and fourth coils L43 and L44. Inductances of the coils L41, L42, L43, and L44 and the equipment for measuring the harmonic wave currents are the same as in the first embodiment.

Test data appearing in Figure 13 is obtained from the circuit for attenuating harmonic wave currents according to the fourth embodiment. As shown by the data, the measured results of the fourth embodiment indicate that IEC regulations are met. Figure 14 shows the load current according to the test data of Figure 13.

Testing System for Measuring Harmonic Wave Currents Figure 15 is a block diagram of a testing system for measuring the second to fortieth harmonic wave currents generated from a load of a circuit for controlling the switching of AC power. When three-phase AC power is inputted to the testing system, an ANIX-SERIES MAGNETICS MODULE 152 and an ANIX-SERIES AC POWER SOURCE 154, made by the Pacific Company of the U. S., stably supplies the AC power to the system. Also, an IEC STANDARD 555 REFERENCE IMPEDANCE NETWORK 156 made by the VOLTech Company of England is used to measure the voltage and current, and a PM3300 UNIVERSAL POWER ANALYZER 158 manufactured by the same company is used to analyze the AC power. A load 162 is a 1400-watt motor which is used in a cleaner made by SAMSUNG Electronics Co. Ltd of Korea. As a test condition, single phase AC power at 230V/501-1z is inputted into the apparatus 160 for attenuating the harmonic wave currents.

- 22 Fifth Embodiment Figure 16 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a fifth embodiment of the present invention. The fifth embodiment is identical to the first embodiment except for the structure of first and second filters 178 and 180. Further, the fifth embodiment is modified from the second embodiment.

Namely, the first filter 178 comprises a first coil L51 and a first resistor lo R51 connected parallel to the first coil L5 1, and the second filter comprises a second coil L52 and a second resistor R52 connected parallel to the second coil L52. Although the effects of attenuating the harmonic wave currents of the circuit of the fifth embodiment is less than that of the second embodiment, the circuit of the fifth embodiment is more effective for use with low-capacity loads.

Sixth Embodiment Referring to Figures 17, 18 and 19, shown respectively are a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a sixth embodiment of the present invention, a table of harmonic wave current test data derived from measuring the circuit of the Figure 17, and a graph illustrating load current according to the test data of the Figure 18.

As shown in Figure 17, the circuit for attenuating harmonic wave currents of the sixth embodiment is identical to the first embodiment except that a single filter 188 is provided. The filter 188 is connected to both ends of the AC power source 112.

The filter 188 includes a core (not shown), a first coil L61 connected between the AC power source 112 and the load 114, and a second coil L62 23 connected between the AC power source 112 and the triac 116. An insulating sheet (not shown) is inserted between the first coil L61 and the second coil L62.

The first coil L61 and second coil L62 are wound in opposite directions. Namely, the first coil L61 is wound toward the load 114 from the AC power source 112 over a third of the length of a core (not shown). Moreover, the number of times the first coil L61 is wound is a third of that of the second coil L62.

One terminal, or end, of the first coil L6 1, at which point the winding of the 10coil L61 begins, is connected to the load 114, while another terminal of the first coil L6 1, at which point the winding of the coil L61 ends, is connected to the AC power source 112. Terminals of the second coil L62 are connected according to the winding direction of the same.

is Electrical characteristics of the coils L61 and L62 used in the sixth embodiment are as follows.

Inductances of the first coil L61 and second coil L62 are 2.4OmH and 4. 0OmH, respectively, and quality factors of the first and second coils are Q61 5.5 and Q62 5.4, respectively. The resistance of the first coil L61 and second coil L62 are respectively 0.8ohm and 1.65ohm, and the distortion factors of the first and second coils are 0.186 and 0.190, respectively. Except these conditions, the measuring conditions and equipment used are the same as in the first embodiment.

Test data appearing in Figure 19 is obtained from the circuit for attenuating harmonic wave currents according to the sixth embodiment. As shown by the data, the measured results of the sixth embodiment indicate that IEC regulations are met.

24 The sixth embodiment has economic advantages over the first embodiment because only a single filter is used in the sixth embodiment.

Seventh Embodiment Figure 20 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a seventh embodiment of the present invention. As shown in the drawing, the circuit for attenuating hannonic wave currents of the seventh embodiment is identical to the first embodiment except that a single filter lo 198 is provided, thereby being a modification of the sixth embodiment. The filter 198 is connected to both ends of the AC power source 112.

In the drawing, the filter 198 includes a first coil L71 connected between the AC power source 112 and the load 114, and a second coil L72 connected between the AC power source 112 and the triac 116. The first coil L71 and second coil L72 are wound in the same direction.

The effects of attenuating harmonic wave currents in the seventh embodiment is slightly less than that realized in the sixth embodiment.

- 25 Eighth Embodiment Figure 21 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with an eighth embodiment of the present invention. As shown in the drawing, the circuit for attenuating harmonic wave currents of the eighth embodiment is identical to the first embodiment except that a single filter 208 is provided, thereby being a modification of the sixth embodiment. The filter 208, unlike the first embodiment, is connected between the AC power source 112 and the load 114.

The filter 208 includes first and second coils L81 and L82 which are wound around a core (not shown) and stacked one on top of the other in a parallel fashion.

The test conditions for measuring the harmonic wave current are the same as in the first embodiment, thereby meeting IEC regulations.

Ninth Embodiment Figure 22 is a schematic diagram of a circuit for attenuating harmonic wave current in accordance with a ninth embodiment of the present invention. As shown in the drawing, the circuit for attenuating harmonic wave currents of the ninth embodiment is identical to the first embodiment except that a single filter 218 is provided, thereby being a modification of the sixth embodiment. The filter 218 is connected between the AC power source 112 and the load 114 as in the 2s eighth embodiment. The filter 218 includes a core (not shown) and a coil L9 1.

26 Tenth Embodiment Figure 23 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a tenth embodiment of the present invention. As shown in the drawing, the circuit for attenuating harmonic wave currents of the tenth embodiment is identical to the first embodiment except that a single filter 228 is provided, thereby being a modification of the sixth embodiment. The filter 228 is connected between the AC power source 112 and the load 114 as in the eighth embodiment. The filter 228 includes a core (not shown), first, second and lothird coils L 10 1, L 102, L 103 which are wound around the core and stacked one on top of the other. The first, second and third coils L101, L102 and L103 are connected parallel to each other. Also, an insulating sheet (not shown) is inserted between the coi Is L 10 1, L 102 and L 103.

Eleventh Embodiment Figure 24 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with an eleventh embodiment of the present invention. As shown in the drawing, the circuit for attenuating harmonic wave currents of the eleventh embodiment is identical to the first embodiment except that a single filter 238 is provided, thereby being a modification of the sixth embodiment. The filter 238 is connected between the AC power source 112 and the load 114 as in the eighth embodiment. The filter 23 8 includes a core (not shown), a coil L 111 wound around the core, and a resistor R 111 connected to the coil L 111.

27 - Twelfth Embodiment Figure 25 is a schematic diagram of a circuit for attenuating harmonic wave currents in accordance with a twelfth embodiment of the present invention. As shown in the drawing, the circuit for attenuating harmonic wave currents of the twelfth embodiment is identical to the first embodiment except that a single filter 248 is provided, thereby being a modification of the sixth embodiment. The filter 248 is connected between the AC power source 112 and the load 114 as in the eighth embodiment. The filter 248 includes a core (not shown), first and second lo coils L121 and L122, and a resistor R121 which is connected parallel to the coils L 121 and L 122. The circuit of the twelfth embodiment can be used in attenuating the harmonic wave currents generated from a load having a low electrical capacity.

Referring now to Figure 26, shown is test data comparing the various embodiments of the present invention structured as in the above with the prior art.

As shown in Figure 26, the effectiveness of the inventive circuit for attenuating harmonic wave currents is varied according to the pattern of connection of the filters and coils.

In the present invention, the inventive circuit for controlling the switching of AC power using the triac effectively stabilizes input AC power and attenuates non-sinusoidal wave currents, i.e. harmonic wave currents, which are generated when the phase of a load is controlled in electrical and electronic devices including motors used in the load, by connecting the coil or coils to the nearest place from the load using the reiteration- correspondence of the inductance of the coil.

28 -

Claims

1. In a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising: an AC power source; a load driven by the AC power source; a triac: controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents in the power supply lo experienced by the load; wherein the means for attenuating harmonic wave currents includes a first filter connected to one end of the AC power source and a second filter connected to another end of the AC power source; and wherein the first filter includes a first core, a first coil wound around the is first core, and a first resistor connected parallel to the first coil; and the second filter includes a second core, a second coil wound around the second core, and a second resistor connected parallel to the second coil.

2. A circuit for attenuating harmonic wave currents as set forth in Claim 1, wherein the first coil is wound toward the load ftom the AC power source; and the second coil is wound toward the AC power source from the load.

3. In a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising an AC power source; a load driven by the AC power source; a triac controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents in the power supply experienced by the load; 29 wherein the means for attenuating harmonic wave currents includes a first filter connected to one end of the AC power source and a second filter connected to another end of the AC power source; and wherein the first filter includes a first core, and first and second coils wound around the first core and stacked one on top of the other; and the second filter includes a second core, and third and fourth coils wound around the second core and stacked one on top of the other.

4. A circuit for attenuating harmonic wave currents as set forth in Claim 3, lo wherein the first and second coils of the first filter are connected parallel to each other; and the third and fourth coils of the second filter are connected parallel to each other.

5. A circuit for attenuating harmonic wave currents as set forth in Claim 3, wherein the first and third coils are wound toward the load from the AC power source by the right hand rule; and the second and fourth coils are wound toward the AC power source from the load by the right hand rule.

6. A circuit for attenuating harmonic wave currents as set forth in Claim 3, wherein the first filter includes a first core, and a first coil wound around the first core; and the second filter includes a second core, and a second coil wound around the second core.

7. A circuit for attenuating harmonic wave currents as set forth in Claim 6, wherein the first coil is wound toward the load from the AC power source by the right hand rule; and the second coil is wound toward the AC power source from the load by the right hand rule.

8. A circuit for attenuating harmonic wave currents as set forth in Claim 3, s wherein the first filter includes a first core, and first and second coils and a first additional coil which are wound around the first core and stacked on top of each other; and the second filter includes a second core, and third and fourth coils and a second additional coil, which are around the second core and stacked on top of lo each other.

is 9. A circuit for attenuating harmonic wave currents as set forth in Claim 8, wherein the first, second and first additional coils are wound toward the load from the AC power source by the right hand rule; and the third, fourth and second additional coils are wound toward the AC power source from the load by the right hand rule.

10. A circuit for attenuating harmonic wave currents as set forth in Claim 8, wherein the first, second and first additional coils of the first filter are connected parallel to each other; and the third, fourth and second additional coils of the second filter are connected parallel to each other.

A circuit for attenuating harmonic wave currents as set forth in Claim 3, wherein the first filter includes a first core, first and second coils wound around the core and stacked one on top of the other and connected parallel to each other, and a first resistor connected parallel to the first and second coils; and the second filter includes a second core, third and fourth coils wound around the second core and stacked one on top of the other and connected parallel to each other, and a second resistor connected parallel to the third and fourth coils.

31 12. A circuit for attenuating harmonic wave currents as set forth in Claim 11, wherein the first and second coils are wound toward the load from the AC power source; and 5 the third and fourth coils are wound toward the AC power source ftom the load.

13. In a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising: an AC power source; a load driven by the AC power source; a triac controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents in the power supply 15 experienced by the load; wherein the means for attenuating the harmonic wave currents includes a filter connected to opposing ends of the AC power source; and the filter includes a core, a first coil connected between the AC power source and the load, and a second coil connected between the AC power source 20 and the triac, and wherein the first coil is wound around the core toward the load from the AC power source by the right hand rule; the second coil is wound around the core toward the AC power source from the load by the right hand rule; and 25 one terminal of the first coil, at which point the winding of the first coil begins, is connected to the load, while another terminal of the first coil, at which point the winding of the first coil ends, is connected to the AC power source.

32 - 14. A circuit for attenuating harmonic wave currents as set forth in Claim 13, wherein a number of times the first coil is wound is one-third that of the second coil.

15. A circuit for attenuating harmonic wave currents as set forth in Claim 13 wherein the first and second coils are wound in a same direction.

16. A circuit for attenuating harmonic wave currents as set forth in Claim 15 wherein the first and second coils are wound toward the load from the AC power lo source by the right hand rule.

is 1 17. In a circuit for controlling the switching of the AC power, a circuit for attenuating harmonic wave currents comprising: an AC power source; a load driven by the AC power source; a triac controlling the switching of AC power supplied to the load by a signal inputted to its gate; and means for attenuating harmonic wave currents, in the power supply experienced by the load; wherein the means for attenuating the harmonic wave currents includes a filter, the filter being connected between the AC power source and the load and wherein the filter includes a core, and first and second coils wound around the core and stacked one on top.of the other, 18. A circuit for attenuating harmonic wave currents as set forth in Claim wherein the filter includes a core and a coil wound around the core.

17, 19. A circuit for attenuating harmonic wave currents as set forth in Claim 17, wherein the filter includes a core, and first and second coils and an additional coil 3o wound around the core and stacked on top of each other.

33 20. A circuit for attenuating harmonic wave currents as set forth in Claim 17, wherein the filter includes a core, a coil wound around the core, and a resistor connected to the coil.

21. A circuit for attenuating harmonic wave currents as set forth in Claim 17, wherein the filter includes a core, first and second coils wound around the core, and a resistor connected to the first and second coils in parallel.

lo 22. A circuit for attenuating harmonic wave currents as set forth in any one of Claims 17 to 2 1, wherein each coil of the filter is wound toward the load from the AC power source by the right hand rule.

23. A circuit for attenuating harmonic wave currents substantially as hereinbefore described with reference to any one of Figures 5 to 21 and 23 to 26.