F2008-06-050
Development of a Current Evaluation Methodology by the Optical Fiber Sensor for Small Design of Hybrid Vehicle Inverters
Hybrid Vehicles (HVs) are great CO2 emission reduction and realization of high driving performance. Expectation HVs are being actively developed. To minimize the size of HV components has the most significant impact on a diffusion of the HV production, and that is also one of the main challenges in HV development. In order to meet this challenge, the technology to evaluate accurately the transient electrical characteristic of the HV components has been needed. Therefore, we have developed a current evaluation methodology that can evaluate the instantaneous current behavior of the silicon chip in the compact HV inverter. In this paper, we will describe this measurement and analysis technology of the current in HV inverters by using the Optical current sensor as the latest evaluation technology even in the power electronics field. The issue of conventional current sensor is that the current is not measured accurately for each parallel power devices in the HV inverter module without a structure altered to experiment because the sensor is too big to probe at the inside of the inverter. At first we tried to put some Shunt Resistors of 0.1m ohm in the inverter package, but the measurement was impossible due to the effect of the current resonance on the Shunt Resistors. Next, we tried to make the Rogowski coil that is an 'air-cored' toroidal coil placed round the conductor, but the measurement result was not enough to evaluate current balance of a few ampere due to error effect by external magnetic field. Then we have focused on the Optical current sensor utilized for electric power industry for those problems. This sensor utilizing the Faraday of an optical fiber is able to measure the current high accuracy without the effect of magnetic field. Furthermore, this one features thin and soft structure to wind the wire bonding a chip in the inverter. However possible bands width of frequency on this sensor was between five kHz and fifty kHz that is too low to measure the current on the HV inverters including a few MHz of current frequency. Then we have solved the technical issue with the improvement of frequency characteristic of circuit component and optimizing gain and frequency response for the Amplifier. Also we combined the measurement method that is the inverter DC operation and average measurement result to reduce the noise current. As a result, the current measurement is now available for parallel chip in the HV inverter, moreover the accuracy of the current simulation technology to design advanced greatly too. Both developed technologies are a very valuable for creating optimum HV inverter compact design.
Session: Hybrid Powertrains II