Apparatus and method for voltage control

摘要

A voltage provided to a load 230 is controlled using a transformer 210 having primary 211 and secondary 212 windings in circuit between an AC electrical supply and the load. A switching device such as relay 240 selectively connects primary winding 211 to the AC electrical supply in either a first configuration where voltage output from the secondary winding is subtracted from the electrical supply voltage, or a second configuration, where the voltage output from the secondary winding is added to the electrical supply voltage. The configuration may be selected depending on whether a supply voltage is less than a threshold. Voltage supplied to the primary winding may be continuously regulated responsive to the supply voltage using a power converter 220. A bypass switch 243 may divert the supply directly to the load in response to a measured current or a temperature of the transformer. A thermal cut-out 260 may disconnect the secondary in response to transformer temperature. The supply voltage may be either increased or reduced to improve efficiency.