Hybrid tap-changing transformer with full range of control and high resolution
AssigneeRobicon Corporation
InventorPeter Hammond
Life of this patent
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Abstract
A hybrid tap-changer for delivering AC power to a load in which a high-power tap-changing transformer with full range of adjustment but limited resolution is combined with a low-power electronic converter of limited range but high resolution to provide a tap-changing transformer with high resolution.
Claims22
A hybrid tap-changer for providing adjustable AC voltage to a load of defined maximum power, comprising:
- a main transformer, having a secondary winding with a plurality of taps, each of said taps providing a tap voltage;
- a plurality of switches, connected to said taps for selecting said taps;
- and
- a controllable voltage source, coupled so that its output is added to or subtracted from said selected tap voltage.
In a device for providing adjustable AC voltage to a load having a main transformer with a secondary winding with a plurality of taps, a plurality of switches, connected to said taps for selecting said taps, said taps divided into a first group comprised of alternating taps and a second group comprised of adjacent alternating taps, said first group of taps being coupled to one side of the secondary winding of an auxiliary transformer and said second group of taps being coupled to the opposite side of the secondary winding of said auxiliary transformer, and a controllable voltage source coupled to the primary winding of said auxiliary transformer, a method of varying said AC voltage comprising:
- raising said voltage from said controllable voltage source until the differential voltage between the currently selected tap and an adjacent tap is reached;
- closing said switch connected to said adjacent tap;
- opening said switch connected to said currently selected tap;
- lowering said voltage from said controllable voltage source until zero volts is reached;
- and
- reversing the polarity of said voltage from said controllable voltage source.
In a device for providing adjustable AC voltage to a load having a main transformer with a secondary winding with a plurality of taps, a plurality of switches, connected to said taps for selecting said taps, said taps divided into a first group comprised of alternating taps and a second group comprised of adjacent alternating taps, said first group of taps being coupled to one side of the winding of an auto-transformer and said second group of taps being coupled to said opposite side of the winding of an auto-transformer, an improvement comprising:
- a primary winding coupled to said winding of said auto-transformer;
- and
- a controllable voltage source coupled to the primary winding of said auto-transformer.
Dependencies are inferred from the claim text.