Claims
- 1. A method of monitoring the temperature of a transformer winding in a current probe wherein the current probe includes a magnetic core having a multi-turn winding disposed there-around forming a probe transformer and a Hall Effect device disposed within the magnetic core for generating a differential output signal for producing a current signal through the multi-turn winding, the method comprising:
determining an initial transformer temperature of the current probe as a function of the winding resistance of the transformer; determining a relative temperature of the Hall Effect device as a function of resistance change of the Hall Effect device; and combining the initial transformer temperature and the relative Hall Effect device temperature to produce a continuous transformer temperature indicative of the temperature of the transformer.
- 2. The method of monitoring the temperature of a transformer winding in a current probe as recited in claim 1 further comprising the step of removing the current signal from the multi-turn winding when the continuous transformer temperature exceeds a threshold temperature value.
- 3. The method of monitoring the temperature of a transformer winding in a current probe as recited in claim 2 further comprising the step of providing a visual indication when the continuous transformer temperature exceeds a threshold temperature value.
- 4. The method of monitoring the temperature of a transformer winding in a current probe as recited in claim 1 wherein the initial transformer temperature determining step further comprises the steps of:
storing the thermal coefficient of copper, α, an initial transformer temperature, T0, and a termination resistance, Rtermination, in memory; generating digital values representative of an input voltage, Vin, to the multi-turn winding and an output voltage, Vout, from the multi-turn winding; calculating an initial probe resistance, R0, using the termination resistance and the digital values of the input and output voltages; and calculating the initial transformer temperature, Tprobe, using the function 7Tprobe=T0+1α(Rtermination(Vin-Vout)-R0VoutR0Vout)
- 5. The method of monitoring the temperature of a transformer winding in a current probe as recited in claim 1 wherein the relative temperature of the Hall Effect device determining step further comprises the steps of:
storing a thermal coefficient of resistance value of the Hall Effect device, αH, a Hall Effect device bias voltage source value, VBias+, and a resistance bias value, RBias, in memory; generating a digital value representative of a voltage, VHall+, across the Hall Effect device; calculating an initial Hall Effect device resistance value, RHall, using the function 8RHall=(2×VHall+RBiasVBias+-VHall+) and storing the resistance value in memory as RHall Init.; generating additional digital values representative of the voltage, VHall+ and calculating Hall Effect resistance values, RHall, representing changes in the resistance of the Hall Effect device as a function of temperature; and calculating changes in temperature of the Hall Effect device, ΔTprobeHall, using the function 9Δ TprobeHall=1αH(RHall-RHall Init.RHall Init.)
- 6. The method of monitoring the temperature of a transformer winding in a current probe as recited in claim 1 wherein the relative temperature of the Hall Effect device determining step further comprises the steps of:
storing first and second thermal coefficient of resistance values of the Hall Effect device, k1 and k2, a Hall Effect device bias voltage source value, VBias+, and a resistance bias value, RBias, in memory; generating a digital value representative of a voltage, VHall+, across the Hall Effect device; calculating an initial Hall Effect device resistance value, RHall, using the function 10RHall=(2×VHall+RBiasVBias+-VHall+) and storing the resistance value in memory as RHall Init.; generating additional digital values representative of the voltage, VHall+ and calculating Hall Effect resistance values, RHall, representing changes in the resistance of the Hall Effect device as a function of temperature; and calculating changes in temperature of the Hall Effect device, ΔTprobeHall, using the function ΔTprobeHall=k1(RHall−RHall Init.)+k2(RHall−RHall Init.)2.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of the U.S. Provisional Application No. 60/428,649, filed Nov. 22, 2002.
Provisional Applications (1)
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Number |
Date |
Country |
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60428649 |
Nov 2002 |
US |