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US 4,357,524 AGranted
Electrical heater controller for aircraft window heat control
AssigneeWestinghouse Electric Corp.
InventorsOtto L. Apfelbeck, Joseph M. Urish
Life of this patent
Estimating the term…
Abstract
A controller system using high frequency switching by providing a bilateral switch gated on and off at a frequency about ten times the source frequency and the duty cycle determined by pulse width modulation of the high frequency waveform in accordance with window heater temperature.
Claims5
An electrical resistance heater controller, for controlling application of power from an AC source to a heating element, comprising:
- bilateral switching means for maintaining or interrupting the circuit between the source and the heating element;
- gating means for turning said switching means on and off periodically at a frequency at least about an order of magnitude higher than the source power frequency, said gating means being receptive of and responsive to a temperature signal from a sensor proximate said heating element, and said gating means controlling the on to off ratio of conduction of said switching means within each high frequency segment;
- and
- input filter means connected on the source side of said switching means for providing a low impedance path for harmonics generated by said switching means.
1 more element
A window heat controller system particularly for aircraft window heat control comprising:
- an AC generator producing power at a first frequency;
- an electrical resistance heating element connected to receive controlled power from said generator and associated with temperature sensing means for developing a DC signal proportional to the temperature of said heating element;
- controller means for switching the generator power at a high frequency of at least about ten times said first frequency and for maintaining the conduction path between said generator and said heating element on during a portion of each high frequency cycle when said temperature signal is below a reference signal level that varies unidirectionally between minima at said high frequency;
- input filter means connected between said generator and said controller means for providing a low impedance path for harmonics generated by said switching means;
- and,
- output filter means for attenuating harmonics generated by said heating element and its associated conductors.
3 more elements
Dependencies are inferred from the claim text.