Transformers having screen layers to reduce common mode noise

1. A transformer comprising:

at least one transformer core;

at least one primary winding layer wound about the transformer core, the at least one primary winding layer including a first primary winding layer and a second primary winding layer;

a first secondary winding layer wound about the transformer core the first secondary winding layer including a secondary winding wire having a width and a number of turns per layer;

at least one auxiliary winding layer wound about the transformer core; and

at least one screen layer wound about the transformer core, the at least one screen layer including a first screen layer and a second screen layer the at least one screen layer including a screen wire having substantially the same width as the secondary winding wire and substantially the same number of turns as the first secondary winding layer to reduce common mode noise in the first secondary winding layer, the at least one screen layer including a grounding connection for grounding the at least one screen layer;

wherein the respective winding and screen layers wound about the transformer core in an order of the first primary winding layer, the auxiliary winding layer, the first screen layer, the first secondary winding layer, the second screen layer, and the second primary winding layer.

2. The transformer of claim 1 , wherein the at least one screen layer comprises enameled copper.

3. The transformer of claim 1 , wherein the at least one screen layer comprises enameled foil.

4. The transformer of claim 1 , wherein the at least one screen layer comprises flat parallel bonded multifilar enameled wire.

5. The transformer of claim 1 , wherein the at least one primary winding layer includes a primary winding wire;

wherein the first secondary winding layer includes a secondary winding wire; and

wherein at least one of the primary winding wire and the secondary winding wire comprises multi-strand Litz wire.

6. The transformer of claim 1 , wherein:

the at least one primary winding layer includes a first primary winding layer and a second primary winding layer;

the at least one screen layer includes a first screen layer, and a second screen layer; and

the respective winding and screen layers are wound about the transformer core in an order of the first primary winding layer, the first screen layer, the secondary winding layer, the second screen layer, the second primary winding layer, and the auxiliary winding layer.

7. The transformer of claim 1 , wherein a voltage between the at least one screen layer and the at least one secondary winding layer is zero during normal operation of the transformer.

8. The transformer of claim 1 , wherein the at least one screen layer further comprises a third screen layer wound outside the second primary winding layer.

9. The transformer of claim 8 , further comprising a second secondary winding layer wound outside the third screen layer.

10. The transformer of claim 9 , further comprising a fourth screen layer wound outside the second secondary winding layer.

11. The transformer of claim 10 , wherein the fourth screen layer is an outer layer of the transformer to provide a voltage to the auxiliary winding layer.

12. A transformer comprising:

at least one transformer core;

at least one primary winding layer wound about the transformer core, the at least one primary winding layer including a first primary winding layer and a second primary winding layer;

at least one secondary winding layer wound about the transformer core, the at least one secondary winding layer including a secondary winding wire having a width and a number of turns per layer, the at least one secondary winding layer including a first secondary winding layer and a second secondary winding layer;

at least one auxiliary winding layer wound about the transformer core; and

at least one screen layer wound about the transformer core and disposed between the at least one primary winding layer and the at least one secondary winding layer, the at least one screen layer including a screen wire having substantially the same width as the secondary winding wire and substantially the same number of turns as the at least one secondary winding layer to reduce common mode noise in the at least one secondary winding layer, the at least one screen layer including a first screen layer, a second screen layer, a third screen layer, and a fourth screen layer, the respective winding and screen layers wound about the transformer core in an order of the first primary winding layer, the auxiliary winding layer, the first screen layer, the first secondary winding layer, the second screen layer, the second primary winding layer, the third screen layer, the second secondary winding layer, and the fourth screen layer.

13. A transformer comprising:

at least one transformer core;

at least one primary winding layer wound about the transformer core, the at least one primary winding layer including a first primary winding layer and a second primary winding layer;

at least one secondary winding layer wound about the transformer core, the at least one secondary winding layer including a secondary winding wire having a width and a number of turns per layer;

at least one auxiliary winding layer wound about the transformer core; and

at least one screen layer wound about the transformer core and disposed between the at least one primary winding layer and the at least one secondary winding layer, the at least one screen layer including a screen wire having substantially the same width as the secondary winding wire and substantially the same number of turns as the at least one secondary winding layer to reduce common mode noise in the at least one secondary winding layer, the at least one screen layer including a first screen layer, and a second screen layer, the respective winding and screen layers wound about the transformer core in an order of the first primary winding layer, the auxiliary winding layer, the first screen layer, the secondary winding layer, the second screen layer, and the second primary winding layer.

14. A method of winding a transformer, the transformer including a core, at least one primary winding layer, at least one secondary winding layer, and at least one screen layer, the method comprising:

winding the at least one primary winding layer about the core of the transformer;

winding the at least one secondary winding layer about the core of the transformer, the at least one secondary winding layer including a secondary winding wire having a width;

winding the at least one screen layer about the core of the transformer so the at least one screen layer is disposed between the at least one primary winding layer and the at least one secondary winding layer, the at least one screen layer including a screen wire having a substantially same width as the width of the secondary winding wire and substantially the same turns per layer as the at least one secondary winding layer to reduce common mode noise in the at least one secondary winding layer, the screen layer including a grounding connection for grounding the screen layer;

winding at least one auxiliary winding layer about the core of the transformer; and

wherein:

winding the at least one primary winding layer includes winding the at least one primary winding layer adjacent the core of the transformer;

winding the at least one auxiliary winding layer includes winding the at least one auxiliary winding layer about the at least one primary winding layer;

winding the at least one screen layer includes winding the at least one screen layer about the at least one auxiliary winding layer; and

winding the at least one secondary winding layer includes winding the at least one secondary winding layer about the at least one screen layer.

15. A method of winding a transformer, the transformer including a core, at least one primary winding layer, at least one secondary winding layer, and at least one screen layer, the method comprising:

winding the at least one primary winding layer about the core of the transformer;

winding the at least one secondary winding layer about the core of the transformer, the at least one secondary winding layer including a secondary winding wire having a width;

winding the at least one screen layer about the core of the transformer so the at least one screen layer is disposed between the at least one primary winding layer and the at least one secondary winding layer, the at least one screen layer including a screen wire having a substantially same width as the width of the secondary winding wire and substantially the same turns per layer as the at least one secondary winding layer to reduce common mode noise in the at least one secondary winding layer, the screen layer including a grounding connection for grounding the screen layer;

winding a second screen layer about the at least one secondary winding layer;

winding a second primary winding layer about the second screen layer; and

winding a third screen layer about the second primary winding layer;

winding a second secondary winding layer about the third screen layer; and

winding a fourth screen layer about the second secondary winding layer.