PROTECTION OF PERMANENT MAGNENTS IN A DC-INDUCTOR

• US 20080303619A1
• Filed: 05/19/2008
• Published: 12/11/2008
• Est. Priority Date: 06/08/2007
• Status: Active Grant

• Current Assignee: ABB Schweiz AG (ABB Limited)
• Original Assignee: Abb Oy (ABB Limited)
• Inventors: VIITANEN, Tero, Pieteris, Paulius
• Granted Patent: US 8,035,470 B2
• Time in Patent Office: Days
• US Class Current: 336/110
• CPC Class Codes: H01F 2003/103 Magnetic circuits with permanent magnets
• CPC Class Codes: H01F 27/38 Auxiliary core members; Auxiliary coils or windings
• CPC Class Codes: H01F 27/402 Association of measuring or protective means
• CPC Class Codes: H01F 29/146 Constructional details
• CPC Class Codes: H01F 3/12 Magnetic shunt paths
• CPC Class Codes: H01F 3/14 Constrictions; Gaps, e.g. air-gaps in magnetic shunt paths H01F3/12
• CPC Class Codes: H01F 37/00 Fixed inductances not covered by group H01F17/00

Abstract

A DC inductor comprising a core structure (11) comprising one or more magnetic gaps (12), a coil (14) inserted on the core structure (11), at least one permanent magnet (15) positioned in the core structure, the magnetization of the permanent magnet (15) opposing the magnetization producible by the coil (14). The core structure is adapted to form a main flux path and an auxiliary flux path, where the main flux path is adapted to carry the main magnetic flux producible by the coil, wherein the auxiliary flux path comprises a magnetic gap and is adapted to lead magnetic flux past the at least one permanent magnet (15).

Claims

1. A DC inductor comprising:

a core structure comprising one or more magnetic gaps,

a coil inserted on the core structure,

at least one permanent magnet positioned in the core structure, the magnetization of the permanent magnet opposing the magnetization producible by the coil, wherein

the core structure is adapted to form a main flux path and an auxiliary flux path, where the main flux path comprising a magnetic gap is adapted to carry the main magnetic flux producible by the coil,

wherein the auxiliary flux path comprising a magnetic gap is adapted to lead magnetic flux passing by the at least one permanent magnet, and to protect the permanent magnet from complete demagnetization.

2. The DC inductor according to claim 1,

wherein the reluctance defined by the magnetic gaps in the main flux path is smaller than the reluctance defined by the magnetic gap in the auxiliary flux path.

3. The DC inductor according to claim 2,

wherein the reluctance defined by the magnetic gap in the auxiliary flux path is smaller than the effective reluctance defined by the permanent magnets.

4. The DC inductor according to claim 1, wherein the auxiliary flux path is formed of a supporting member made of magnetic material, which supporting member extends from the core structure inside the winding window of the core structure and holds the at least one permanent magnet.

5. The DC inductor according to claim 4,

wherein the supporting member extends inside the winding window of the core structure towards a part of the core structure and that the supporting member has a free end which defines together with the part of the core structure the magnetic gap in the auxiliary flux path.

6. The DC inductor according to claim 2, wherein the supporting member is arranged to extend parallel to the core structure and the at least one permanent magnet is arranged between the supporting member and the core structure such that the at least one supporting member together with the core structure forms a low reluctance magnetic path for the at least one permanent magnet.

7. The DC inductor according to claim 1, wherein at least one magnetic slab is used to define the magnetic gap in the main flux path.

8. The DC inductor according to claim 2, wherein

the core structure comprises an upper leg and that

the supporting member extends parallel to the upper leg inside the core structure, the distance between the upper leg and the supporting member corresponding to the dimension of the at least one permanent magnet.

9. The DC inductor according to claim 1, wherein the DC inductor further comprises fault detection means, which are adapted to sense current of the coil and/or flux of the core structure

10. The DC inductor according to claim 9,

wherein the fault detection means sensing the flux are arranged in a magnetic gap provided in the main flux path or auxiliary flux path.

11. The DC inductor according to claim 1, wherein the DC inductor further comprises temperature detection means, which are adapted to sense the temperature of the core structure.