| 摘要 |
Variable inductance ballast apparatus for high-intensity discharge (HID) lamp comprises a laminated E-I core having non-magnetic gaps intermediate the E-conformed and I-conformed members. A main winding is carried on a leg of the E-conformed member to provide two closed magnetic paths. A control winding is wrapped about another of the legs and encircles only one of the closed magnetic paths. A bilateral switch connects to the control winding and is actuated by a signal-generating means which is responsive to a lamp operating condition to close the bilateral switch once each half cycle of energizing potential during normal lamp operation, with the resulting counter mmf decreasing the inductance of the ballast apparatus by a predetermined amount to control in a very accurate, simple and inexpensive fashion the average power delivered to the lamp. |
