Electric heating – Heating devices – With current connection and/or disconnection means
Patent
1988-08-04
1991-04-16
Paschall, M. H.
Electric heating
Heating devices
With current connection and/or disconnection means
219502, 219494, 219497, 323236, 361160, 361195, H05B 102
Patent
active
050085166
ABSTRACT:
A relay control for a cooking appliance having a heating element includes a sensor for detecting the occurrence of an arc upon a change of state of a relay coupled between the heating element and a power supply. Upon detecting an arc, the sensor provides a timing signal which is coupled to a microprocessor that controls the energization and deenergization of the relay. The microprocessor is responsive to the timing signal from the sensor to determine the time delay between the last energization/deenergization of the relay and the changing of the relay's state. From the time delay, the microprocessor determines a delay constant. Subsequently, the microprocessor energizes the relay at a time after the detection of a zero crossover point of the power supply signal, wherein the time is equal to the determined delay constant to cause the relay to change state at or slightly before a zero crossover point of the power supply signal. The sensor may take the form of an optical sensor mounted inside the housing of the relay or outside of the housing. Alternatively, the sensor may include an electromagnetic or RF pick-up coil for sensing an electromagnetic or RF signal in the radio frequency (RF) range radiated upon the generation of an arc. Alternatively, the sensor may be a vibration sensor, such as a piezoelectric transducer, capable of detecting vibrations associated with the opening or closing of the relay contacts.
REFERENCES:
patent: 4348582 (1982-09-01), Budek
patent: 4376243 (1983-03-01), Renn et al.
patent: 4626698 (1986-12-01), Harnden, Jr. et al.
Paschall M. H.
Whirlpool Corporation
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