Ballast filtering scheme for reduced harmonic distortion
First Claim
1. A ballast having an input for receiving from a utility power line, under nominally rated ballast load conditions, an alternating current having a peak amplitude and characterized by a ballast input equivalent impedance ZIN as measured across the ballast input and further comprising a filter characterized by an equivalent impedance Zeq, coupled to the ballast input and including a filter output, an inductor having a core and a capacitor coupled to the output of the filter and at least a portion of the inductor, the core being substantially characterized by a B-H curve having a substantially linear region and a substantially non-linear region with a substantially uniform flux density existing throughout the core when in the non-linear region of its B-H curve, wherein, under nominally rated ballast load conditions, the core operates within the non-linear region of its B-H curve when at least at the peak amplitude of the alternating current and the relationship between the equivalent impedance Zeq and input impedance ZIN is as follows:
- 0.5≦
Zeq /ZIN ≦
1.5.
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Accused Products
Abstract
A ballast filter in which the ballast can operate at a total harmonic distortion of power line current of less than 10%. Power dissipated by the filter when at a THD of less than 10% is relatively low. The input impedance of the ballast is chosen to be no greater than twice the equivalent filter impedance of a front end filter and no less than the equivalent filter impedance/1.5. The filter includes a transformer having a core which at times operates within the non-linear region of its B-H curve under nominally rated ballast load conditions.
29 Citations
16 Claims
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1. A ballast having an input for receiving from a utility power line, under nominally rated ballast load conditions, an alternating current having a peak amplitude and characterized by a ballast input equivalent impedance ZIN as measured across the ballast input and further comprising a filter characterized by an equivalent impedance Zeq, coupled to the ballast input and including a filter output, an inductor having a core and a capacitor coupled to the output of the filter and at least a portion of the inductor, the core being substantially characterized by a B-H curve having a substantially linear region and a substantially non-linear region with a substantially uniform flux density existing throughout the core when in the non-linear region of its B-H curve, wherein, under nominally rated ballast load conditions, the core operates within the non-linear region of its B-H curve when at least at the peak amplitude of the alternating current and the relationship between the equivalent impedance Zeq and input impedance ZIN is as follows:
- 0.5≦
Zeq /ZIN ≦
1.5. - View Dependent Claims (2, 3, 4)
- 0.5≦
-
5. A method of operating a ballast having a ballast input, a ballast input impedance ZIN as measured the across the ballast input and a filter coupled to the ballast input, having a filter output and characterized by an equivalent impedance Zeg, comprising the steps of:
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receiving at the ballast input from a utility power line under nominally rated ballast load conditions an alternating current having a peak amplitude; drawing the alternating current through the filter, the filter further including a capacitor and an inductor having a core, the capacitor being coupled to at least a portion of the inductor and one of the filter output and ballast input, the core being substantially characterized by a B-H curve having a substantially linear region and a substantially non-linear region with a substantially uniform flux density existing throughout the core when in the non-linear region; varying the relationship between the equivalent impedance Zeq and the ballast input impedance ZIN under nominally rated ballast load conditions such that 0.5≦
Zeq /ZIN ≦
1.5; andmaintaining the core within the non-linear region of its B-H curve when at least at the peak amplitude of the alternating current under nominally rated ballast load conditions. - View Dependent Claims (6)
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7. A ballast apparatus comprising:
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input terminals for supplying, under nominally rated ballast load conditions, an alternating current having a peak amplitude, wherein the ballast apparatus has a ballast input equivalent impedance ZIN as measured across the ballast input, a filter coupled to the ballast input and having a filter output, inductor means having a magnetic core and a capacitor coupled to the output of the filter and at least a portion of the inductor means, wherein the filter has an equivalent impedance Zeq and the core is characterized by a B-H curve having a substantially linear region and a substantially non-linear region, and wherein, under nominally rated ballast load conditions, the core operates within the non-linear region of its B-H curve when the inductor means receives the peak amplitude of the alternating current, and the relationship between the equivalent impedance Zeq and the input impedance ZIN is 0.5≦
Zeq /ZIN ≦
1.5. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification