Thermal measuring and testing – Temperature measurement – Combined with diverse art device
Reexamination Certificate
1998-12-16
2001-09-04
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Temperature measurement
Combined with diverse art device
C318S471000, C702S130000
Reexamination Certificate
active
06283631
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electronic device modeling the temperature rise in a motor, making use of current sensors placed on the motor power supply phases.
2. Discussion of the Background
Temperature rises dangerous for a motor may be caused by a low prolonged overload, a slight phase unbalance, excessively long or frequent startups, the motor getting unable to turn, or intermittent conditions. An electronic protection relay takes action by calculating the motor temperature starting from signals supplied by sensors located on each of the power supply phases. This calculation is done taking account of thermal inertia.
The electronic relay described in patent U.S. Pat. No. 3,808,503 comprises a current sensor on each motor power supply phase sending an “image” signal of the phase current to an electronic processing circuit that outputs a current proportional to the square of the motor current, to a circuit modeling the motor temperature rise consisting of an R-C circuit.
SUMMARY OF THE INVENTION
One particular purpose of the invention is to avoid the need to inject a current proportional to the square of the motor current into the motor temperature modeling circuit, as is done in known solutions. This solution gives a wider “customer” adjustment range that can be obtained with known solutions.
The device according to the invention is characterized by the fact that current sensor signals are sent to interface means that output a voltage which is an image voltage of the ratio of the motor current to the adjustment current, and that the calculation means use the said voltage to supply a charge current wave stream, in which the amplitude and duration are each proportional to the above ratio, to the modeling circuit.
REFERENCES:
patent: 3808503 (1974-04-01), Hentschel
patent: 3808516 (1974-04-01), Hentschel
patent: 4547826 (1985-10-01), Premerlani
patent: 4939437 (1990-07-01), Farag et al.
patent: 5539601 (1996-07-01), Farag
patent: 1169501 (1984-06-01), None
patent: 0 237 412 A1 (1987-09-01), None
patent: 0 347 703 A1 (1989-12-01), None
Gousset Alain
Guibert Philippe
Gutierrez Diego
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pruchnic Jr. Stanley J.
Schneider Electric SA
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