SURFACE FILTERS FOR AC SYSTEMS

Description

FIELD OF THE INVENTION

[0001] Single-phase and three-phase alternating current installations, as well as devices that operate with alternating current, such as motors, inverters, transformers and generally all devices that generate harmonics in their normal operation.BACKGROUND OF THE INVENTION

[0002] The harmonic filters of the state of the art are mainly made up of coils and capacitors to eliminate harmonics, especially odd order harmonics starting from the third-order harmonic, which are the most detrimental to single-phase and three-phase alternating current installations.

[0003] Of the two main elements in harmonic filters, capacitors have the greatest weight and size and they also tend to deteriorate.

[0004] Therefore, it would be desirable to find a harmonic filter for single-phase and three-phase alternating current installations that do not have capacitors.

[0005] CA 2 689 029 A1 discloses a device for filtering harmonics in which the inductors can be wound in different directions (i.e. clockwise or counter clockwise), thus affecting the mutual or electromagnetic coupling between the inductors.DESCRIPTION OF THE INVENTION

[0006] To solve the aforementioned problems that are related to the deterioration of capacitors for harmonic filters, the present invention discloses several configurations for the harmonic filter according to different aspects of the invention.

[0007] In a first aspect of the invention, a harmonic filter is disclosed for single-phase alternating current electrical installations, which comprise a phase and a neutral having an "AC" alternating current. The single-phase harmonic filter comprises: a phase input of the filter, which is connectable to a phase output of a single-phase voltage source; a neutral input of the filter, which is connectable to the neutral output of the single-phase voltage source, and is connectable to a neutral input of a single-phase RLC load; a phase output of the filter, which is connectable with a phase input of the single-phase RLC load; a first helical coil, arranged in series between the phase input and the phase output of the filter; a second helical coil, arranged in series between the phase input of the filter and the neutral input of the filter; a ferromagnetic core around which the first helical coil and the second helical coil are wound; where the first helical coil has a winding direction opposite to the winding direction of the second helical coil.

[0008] The single-phase harmonic filter additionally comprises a third helical coil, which has the same winding direction as the second helical coil. Furthermore, the ends of the third helical coil are connected to each other forming a closed circuit.

[0009] In a second aspect of the invention, a harmonic filter is disclosed for three-phase alternating current electrical installations, which comprise three phases and a neutral having an "AC" alternating current. The three-phase harmonic filter comprises: a three-phase phase input of the filter, which is connectable to a three-phase phase output of a three-phase voltage source; a neutral line of the filter; a three-phase phase output of the filter, which is connectable with a three-phase input of a three-phase RLC load; three phase lines, where each phase line joins one phase output of the three-phase phase output to the neutral line; and, a ferromagnetic core; where each phase line comprises: a first helical coil, arranged in series between the three-phase phase input of the filter and the three-phase phase output of the filter; a second helical coil, arranged in series between the three-phase phase input of the filter and the neutral line of the filter; where the first helical coil and the second helical coil are wound around the ferromagnetic core, and where the first helical coil has a winding direction opposite to the winding direction of the second helical coil.

[0010] The three-phase harmonic filter, for each of the phase lines, additionally comprises a third helical coil, where the third helical coil has the same winding direction as the second helical coil, and where some ends of the third helical coil are connected to each other forming a closed circuit.

[0011] The harmonic filter of the present invention can be used as a voltage booster or as a voltage reducer by modifying the turns of the first helical coil and of the second helical coil as is known in the state of the art, giving rise to the aspects of the invention that are listed below.

[0012] In a third aspect of the invention, a single-phase voltage booster is disclosed comprising a harmonic filter according to the first aspect of the invention.

[0013] In a fourth aspect of the invention, a three-phase voltage booster is disclosed comprising a harmonic filter according to the second aspect of the invention.

[0014] In a fifth aspect of the invention, a single-phase voltage reducer is disclosed comprising a harmonic filter according to the first aspect of the invention.

[0015] In a sixth aspect of the invention, a three-phase voltage reducer is disclosed comprising a harmonic filter according to the second aspect of the invention.BRIEF DESCRIPTION OF THE FIGURES

[0016] Figure 1 shows a harmonic filter, according to the present invention, for a single-phase alternating current installation; Figure 2 shows a harmonic filter, according to the present invention, for a three-phase alternating current installation. DESCRIPTION OF VARIOUS EXEMPLARY EMBODIMENTS OF THE INVENTION Reference list.

[0017] 1.Single-phase harmonic filter; 2.Three-phase harmonic filter; 3.Winding direction to the left; 4.Winding direction to the right; 5.Single-phase AC voltage source; 6.Three-phase AC voltage source with phases R,S,T; 6', 6", 6"': three- phase phase lines R, S, T; 7.Single-phase RLC load; 8.Three-phase RLC load; 9.9'.: Ferromagnetic core; 10.First single-phase helical coil; 10', 10", 10‴: first three-phase helical coil for phases R, S and T, respectively; 11.Second single-phase helical coil; 11', 11", 11‴: second three-phase helical coil for phases R, S and T, respectively; 12.Third helical coil of the single-phase filter; 13.Third helical coil of the phase R of the three-phase filter; 14.Third helical coil of the phase S of the three-phase filter; 15.Third helical coil of the phase T of the three-phase filter; 16.Input "R" of the three-phase filter; 16': input "S" of the three-phase filter; 16": input "T" of the three-phase filter; 17.Neutral line of the three-phase filter; 18.Three-phase phase outputs of the filter 2; 18: phase output "R"; 18': phase output "S"; 18": phase output "T"; 19.Phase input "R" of the three-phase RLC load; 19'.: phase input "S" of the three-phase RLC load; 19".: phase input "T" of the three-phase RLC load; 20.Phase input of the single-phase filter; 21.Neutral line of the single-phase filter; 22.Phase input of the single-phase load; 23.Neutral input of the single-phase load;

[0018] Figure 1 shows a single-phase harmonic filter (1) according to an exemplary embodiment of the present invention, where the harmonic filter (1) has two helical coils (10,11) connected in series to each other, and a magnetic core (9) around which both helical coils (10,11) are wound in opposite directions (3,4). Since the helical coils are wound in opposite directions (3,4), the currents generated in the magnetic core have opposite directions, leading to their cancellation, which causes the attenuation, and even complete cancellation, of the odd harmonics of third order and higher.

[0019] The harmonic filter (1) is designed for single-phase alternating current electrical installations, which comprise a phase and a neutral having an "AC" alternating current. Thus, the harmonic filter (1) comprises the first helical coil (10) connected in series with the second helical coil (11), and the magnetic core (9) around which the first helical coil (10) and the second helical coil (11) are wound in opposite directions. The harmonic filter (1) has the phase input of the filter (20) located at the junction between one end of the first helical coil (10) and one end of the second helical coil (11).

[0020] Continuing with Figure 1, it is observed that the phase input of the filter (20) is connected to the phase output (20') of the single-phase AC voltage source (5). The phase output of the filter (22) is located at the other end of the first helical coil (10). The phase output of the filter (22) is connected to the RLC load (7). The neutral line (21) (also called neutral input / output 21) is connected to the neutral output (21') of the single-phase AC voltage source (5) and to the neutral input (23) of the single-phase RLC load (7).

[0021] Finally, and according to the embodiment of Figure 1, the harmonic filter (1) has a third helical coil (12) wound in the same direction as the second helical coil (11), where the ends (12', 12") of the third helical coil (12) are connected to each other forming a "closed circuit". The third helical coil (12) has the technical effect of reducing the energy consumption of the filter (1) when there is no RLC load (7) connected to the output of the filter.

[0022] On the other hand, Figure 2 shows a three-phase harmonic filter (2) according to an exemplary embodiment of the present invention for three-phase alternating current electrical installations, which comprise three phases (6,6',6") and the neutral (17) having an "AC" alternating current. The harmonic filter for three-phase currents (2) shown in Figure 2 comprises: the phase input "R" of the filter (16), which is connectable to the phase output "R" (6') of the three-phase voltage source (6); the phase input "S" of the filter (16'), which is connectable to the phase output "S" (6") of the three-phase voltage source (6); the phase input "T" of the filter (16"), which is connectable to the phase output "S" (6‴) of the three-phase voltage source (6); the neutral line of the filter (17); the phase output "R" of the filter (18), which is connectable to the phase input "R" (19) of the three-phase RLC load (8); the phase output "S" of the filter (18'), which is connectable to the phase input "S" (19') of the three-phase RLC load (8); the phase output "T" of the filter (18"), which is connectable to the phase input "T" (19") of the three-phase RLC load (8); the first helical coil "R" (10'), arranged in series between the phase input "R" (16) and the phase output "R" of the filter (18); the second helical coil "R" (11'), arranged in series between the phase input "R" (16) of the filter and the neutral line of the filter (17); the ferromagnetic core (9') around which the first helical coil "R" (10') and the second helical coil "R" (11') are wound, where the first helical coil (10') has a winding direction (4) opposite to the winding direction (3) of the second helical coil (11'); the first helical coil "S" (10"), arranged in series between the phase input "S" (16') and the phase output "S" of the filter (18'); the second helical coil "S" (11'), arranged in series between the phase input "S" (16') of the filter and the neutral line of the filter (17); where the first helical coil (10") and the second helical coil (11") are wound around the ferromagnetic core (9'), and where the first helical coil "S" (10") has a winding direction (4) opposite to the winding direction (3) of the second helical coil "S" (11"); the first helical coil "T" (10‴), arranged in series between the phase input "T" (16") and the phase output "T" of the filter (18"); the second helical coil "T" (11‴), arranged in series between the phase input "T" (16") of the filter and the neutral line of the filter (17); where the first helical coil "T" (10‴) and the second helical coil "T" (11‴) are wound around the ferromagnetic core (9'), and where the first helical coil "T" (10‴) has a winding direction (4) opposite to the winding direction (3) of the second helical coil "T" (11‴).

[0023] In a similar way to the case of the single-phase filter shown in Figure 1, the three-phase filter (2) shown in Figure 2 has the helical coils wound in opposite directions (3,4). This causes the currents generated in the magnetic core to have opposite directions, leading to their cancellation, which causes the attenuation, and even complete cancellation, of the odd harmonics of third order and higher.

[0024] The three-phase harmonic filter (2) for single-phase alternating current electrical installations shown in Figure 2 additionally comprises the third helical coil "R" (13), which has the same winding direction (3) as the second helical coil "R" (11'). The ends (13', 13") of the third helical coil "R" (13) are connected to each other forming a closed circuit.

[0025] The three-phase harmonic filter (2) for single-phase alternating current electrical installations shown in Figure 2 additionally comprises the third helical coil "S" (14), which has the same winding direction (3) as the second helical coil "S" (11"). The ends (14', 14") of the third helical coil "S" (14) are connected to each other forming a closed circuit.

[0026] The three-phase harmonic filter (2) for single-phase alternating current electrical installations shown in Figure 2 additionally comprises the third helical coil "T" (15), which has the same winding direction (3) as the second helical coil "T" (11"'). The ends (15', 15") of the third helical coil "T" (15) are connected to each other forming a closed circuit.

Claims

1. A harmonic filter for single-phase alternating current electrical installations, which comprise a phase and a neutral having an "AC" alternating current; the filter comprises: • a phase input of the filter (20), which is connectable to a phase output (20') of a single-phase voltage source (5); • a neutral input of the filter (21), which is connectable to the neutral output of the single-phase voltage source (5), and is connectable to a neutral input (23) of a single-phase RLC load (7); • a phase output of the filter, which is connectable with a phase input (22) of the single-phase RLC load (7); • a first helical coil (10), arranged in series between the phase input (20) and the phase output of the filter (22); • a second helical coil (11), arranged in series between the phase input (20) of the filter and the neutral input of the filter (21); • a ferromagnetic core (9) around which the first helical coil (10) and the second helical coil (11) are wound; where the first helical coil (10) has a winding direction (4) opposite to the winding direction (3) of the second helical coil (11); characterised in that the filter further comprises a third helical coil (12), where the third helical coil (12) has the same winding direction (3) as the second helical coil (11), and where ends (12', 12") of the third helical coil (12) are connected to each other forming a closed circuit.

2. A harmonic filter for three-phase alternating current electrical installations, which comprise three phases (6,6',6") and a neutral (17) having an "AC" alternating current; the filter (2) comprises: • a three-phase phase input of the filter (16, 16', 16"), which is connectable to a three-phase phase output (6', 6", 6‴) of a three-phase voltage source (6); • a neutral line of the filter (17); • a three-phase phase output of the filter (18, 18', 18"), which is connectable with a three-phase input (19, 19', 19") of a three-phase RLC load (8); • three phase lines (10', 11'; 10", 11"; 10‴, 11‴), where each phase line joins one phase output of the three-phase phase output (18, 18', 18") to the neutral line (17); and, • a ferromagnetic core (9'); where each phase line (10', 11'; 10", 11"; 10‴, 11‴) comprises: • a first helical coil (10', 10", 10"'), arranged in series between the three-phase phase input of the filter (16, 16', 16") and the three-phase phase output of the filter (18, 18', 18"); • a second helical coil (11', 11", 11‴), arranged in series between the three-phase phase input of the filter (16, 16', 16") and the neutral line of the filter (17); • where the first helical coil (10', 10", 10‴) and the second helical coil (11', 11", 11‴) are wound around the ferromagnetic core (9'), and where the first helical coil (10', 10", 10"') has a winding direction (4) opposite to the winding direction (3) of the second helical coil (11', 11", 11‴); characterised in that, for each of the phase lines (10', 11'; 10", 11"; 10‴, 11‴), the filter further comprises a third helical coil (13, 14, 15), where the third helical coil (13, 14, 15) has the same winding direction (3) as the second helical coil (11', 11", 11‴), and where ends (13',13"; 14',14"; 15',15") of the third helical coil (13, 14, 15) are connected to each other forming a closed circuit.

3. A single-phase voltage booster comprising a harmonic filter according to claim 1.

4. A three-phase voltage booster comprising a harmonic filter according to claim 2.

5. A single-phase voltage reducer comprising a harmonic filter according to claim 1.

6. A three-phase voltage reducer comprising a harmonic filter according to claim 2.