Heating of Solenoids

Abstract

A solenoid comprises first and second coils connected to an electrical power supply circuit. In a first mode of operation the power supply circuit is arranged to provide a current flowing in opposite directions through the respective first and second coils, e.g. to produce a self-heating effect. In a second mode of operation the power supply circuit is arranged to provide a current flowing in the same direction through the respective first and second coils, e.g. to generate a magnetic force. In some embodiments, the power supply circuit includes a bridge rectifier or full wave rectifier connected to a bi-directional current driver.

Claims

1. A solenoid comprising first and second coils connected to an electrical power supply circuit, wherein in a first mode of operation the power supply circuit is arranged to provide a current flowing in opposite directions through the respective first and second coils and in a second mode of operation the power supply circuit is arranged to provide a current flowing in the same direction through the respective first and second coils.

2. The solenoid of claim 1, wherein the first and second coils are both connected to the electrical power supply circuit by a shared pair of electrical connections.

3. The solenoid of claim 1, wherein the electrical power supply circuit comprises a single current driver connected to both of the first and second coils.

4. The solenoid of claim 3, wherein the current driver is a bi-directional current driver.

5. The solenoid of claim 4, wherein the power supply circuit includes a bridge rectifier or full wave rectifier connected to the bi-directional current driver.

6. The solenoid of claim 1, wherein the electrical power supply circuit comprises a first current driver connected to the first coil and a second current driver connected to the second coil.

7. The solenoid of claim 6, wherein at least one of the first and second current drivers is a bi-directional current driver.

8. The solenoid of claim 4, wherein the power supply circuit comprises a controller arranged to control the direction of current provided by the bi-directional current driver.

9. The solenoid of claim 3, wherein a controller is arranged to control the magnitude of current provided by the one or more current drivers.

10. The solenoid of claim 1, wherein the electrical power supply circuit comprises a voltage source connected to both of the first and second coils.

11. The solenoid of claim 10, wherein the power supply circuit further comprises one or more switches arranged to switch the direction of the current supplied by the voltage source to one or both of the first or second coils.

12. The solenoid of claim 1, wherein the current flowing through the first and second coils in the first mode operation is greater than the current flowing through the first and second coils in the second mode operation.

13. The solenoid of claim 1, wherein the first mode of operation is a default mode of operation.

14. A hydraulic solenoid valve comprising the solenoid of claim 1.

15. A method of controlling a solenoid comprising first and second coils connected to an electrical power supply circuit, the method comprising: a first mode of operation wherein the power supply circuit is controlled to provide a current flowing in opposite directions through the respective first and second coils; and a second mode of operation wherein the power supply circuit is controlled to provide a current flowing in the same direction through the respective first and second coils.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0024] One or more non-limiting examples will now be described, with reference to the accompanying drawings, in which:

[0025] FIG. 1 shows a schematic layout for a solenoid and power supply circuit according to a first example;

[0026] FIG. 2 shows a schematic layout for a solenoid and power supply circuit according to a second example;

[0027] FIG. 3 shows a schematic layout for a solenoid and power supply circuit according to a third example; and

[0028] FIG. 4 shows a schematic layout for a solenoid and power supply circuit according to a fourth example.

DETAILED DESCRIPTION

[0029] In the first example seen in FIG. 1, a solenoid comprises a first coil 2 and a second coil 4. Both of the coils 2, 4 are connected to a common current driver 6 in a power supply circuit 8 by a single pair of wires. The power supply circuit 8 may include a controller (not shown). The current driver 6 is a bi-directional current driver that can be controlled to supply current in the circuit 8 in either direction. A full wave rectifier 10 is connected in parallel with the second coil 4. Although not illustrated, it will be appreciated that the full wave rectifier 10 could alternatively be connected in parallel with the first coil 2 instead.

[0030] The solenoid has two modes of operation. In a first mode of operation, represented by the upper set of arrows, the current driver 6 provides a current flowing in a generally clockwise direction in the power supply circuit 8. The full wave rectifier 10 causes the current to pass through the second coil 4 in the opposite direction to the current passing through the first coil 2. This means that the magnetic flux paths created by the two coils 2, 4 are in opposite directions and oppose each other so no magnetic force is generated. Only a self-heating effect is produced in the first mode of operation. In a second mode of operation, represented by the lower set of arrows, the current driver 6 is reversed so that current flows in a generally anti-clockwise direction in the power supply circuit 8. The full wave rectifier 10 causes the current to pass through the second coil 4 in the same direction as the current passing through the first coil 2. This means that the magnetic flux paths created by the two coils 2, 4 are aligned and the solenoid operates to generate a magnetic force.

[0031] In the second example seen in FIG. 2, a solenoid comprises a first coil 2 and a second coil 4 connected to a power supply circuit 8. The first coil 2 is connected to a first current driver 6a and the second coil 4 is connected to a second current driver 6b. The power supply circuit 8 may include a controller (not shown). The first current driver 6a is a bi-directional current driver that can be controlled to supply current to the first coil 2 in either direction. The second current driver 6b is a uni-directional current driver that supplies current to the second coil 4 in an anti-clockwise direction. There is no full wave rectifier in this power supply circuit 8.

[0032] The solenoid has two modes of operation. In a first mode of operation, represented by the upper set of arrows, the bi-directional current driver 6a provides a current flowing in a clockwise direction to the first coil 2, which is in the opposite direction to the current passing through the second coil 4. This means that the magnetic flux paths created by the two coils 2, 4 are in opposite directions and oppose each other so no magnetic force is generated. Only a self-heating effect is produced in the first mode of operation. In a second mode of operation, represented by the lower set of arrows, the bi-directional current driver 6a is reversed so that current flows in an anti-clockwise direction through the first coil 2 i.e. in the same direction as the current passing through the second coil 4. This means that the magnetic flux paths created by the two coils 2, 4 are aligned and the solenoid operates to generate a magnetic force.

[0033] In the third example seen in FIG. 3, a solenoid comprises a first coil 2 and a second coil 4. Both of the coils 2, 4 are connected by a single pair of wires to a common voltage source 106 by a power supply circuit 108. The power supply circuit 108 may include a controller (not shown). The power supply circuit 108 includes a single pair of electrical connections for the two coils 2, 4, each electrical connection including a switch 12a, 12b. The two switches 12a, 12b can both be in a closed position as seen in FIG. 3, or both opened, so as to supply current to the coils 2, 4 in either direction. A full wave rectifier 10 is connected in parallel with the second coil 4. Of course it will be appreciated that the electrical connections could be reversed and the full wave rectifier 10 connected in parallel with the first coil 2 instead.

[0034] The solenoid has two modes of operation. In a first mode of operation, represented by the upper set of arrows, the switches 12a, 12b are moved across from the closed position seen in FIG. 3 so as to provide a current flowing in a generally clockwise direction in the power supply circuit 108. The full wave rectifier 10 causes the current to pass through the second coil 4 in the opposite direction to the current passing through the first coil 2. This means that the magnetic flux paths created by the two coils 2, 4 are in opposite directions and oppose each other so no magnetic force is generated. Only a self-heating effect is produced in the first mode of operation. In a second mode of operation, represented by the lower set of arrows, the switches 12a, 12b are held in the position seen in FIG. 3 so as to provide a current flowing in a generally anti-clockwise direction in the power supply circuit 108. The full wave rectifier 10 causes the current to pass through the second coil 4 in the same direction as the current passing through the first coil 2. This means that the magnetic flux paths created by the two coils 2, 4 are aligned and the solenoid operates to generate a magnetic force.

[0035] In the fourth example seen in FIG. 4, a solenoid comprises a first coil 2 and a second coil 4. Both of the coils 2, 4 are connected by a single pair of wires to a common voltage source 106 by a power supply circuit 208. The power supply circuit 208 includes a pair of electrical connections for each of the first and second coils 2, 4, i.e. four wires in total. The electrical connection for each of the coils 2, 4 includes a switch 12a, 12b. The two switches 12a, 12b can both be in a closed position as seen in FIG. 4, or both opened, so as to supply current to the coils 2, 4 in either direction.

[0036] The solenoid has two modes of operation. In a first mode of operation, represented by the upper set of arrows, the switches 12a, 12b are moved across from the closed position seen in FIG. 4 so as to provide a current flowing in a clockwise direction through the first coil 2, which is in the opposite direction to the current flowing anti-clockwise through the second coil 4. This means that the magnetic flux paths created by the two coils 2, 4 are in opposite directions and oppose each other so no magnetic force is generated. Only a self-heating effect is produced in the first mode of operation. In a second mode of operation, represented by the lower set of arrows, the switches 12a, 12b are in the closed position seen in FIG. 4 so as to provide a current flowing in an anti-clockwise direction through the first coil 2, which is in the same direction as the current flowing through the second coil 4. This means that the magnetic flux paths created by the two coils 2, 4 are aligned and the solenoid operates to generate a magnetic force. The power supply circuit 208 may include a controller (not shown) that acts to open and close the switches 12a, 12b.