| Charging Circuit for a large SC Coil for SMES - UPS System | |
| अन्वेषक | Prof. K. Venkataranthnam; Prof. S. N. Bhardra; Prof. V. V. Rao; Prof. S. Sengupta; Prof. T. K. Bhattacharya and Prof. Dinkar Prasad |
| Patent | Filed |
| Charging circuit for SC coil used in Magnetic Energy Storage systems has to handle large amounts of current (typically hundred or thousand of amperes). Transistorized charging circuits for such high currents are very expensive and complex to build. Another point to be noted is that the tolerant ripple in current in SMES coils is quite high as compared for SC magnets used for MRI & NMR coils where very stable current supply is needed. Keeping these two points in view, namely large amounts of current and less rigidity of ripple content, we have developed a low cost, high current charging circuit using a servo motor controlled 3-phase variac, two step-down transformers and a two 3-phase power diode bridges (to have 12f ripple) and a hall sensor for current control. The whole circuit has been built and tested to charge the 0.5 MJ superconducting magnet at different slew rates and to different current settings (upto 350 A). The slew rate (ramp rate) of current can be varied smoothly to any desired value. A slow-syn stepper motor is used as the control motor.
The circuit developed is far better than the commonly used thyristor bridge circuit, where the amount of ripple current depends on the ramp rate of current and final setting of current. In the circuit developed, the ripple voltage magnitude is constant and nearly level DC current is obtained independent of ramp rate and final setting of current. The circuit is also much cheaper and more rugged. Since the losses in SC coil depend on the ripple content, the charging circuit developed is ideal for SMES - UPS systems. In UPS, the energy stored need not be sent back to the supply and hence reversible power flow devices like thyristors are not necessary and diodes (which are much cheaper and simple devices) will serve the purpose for charging the magnet. |
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| प्रभारी प्राध्यापक, IPR & IR प्रायोजित शोध एवं औद्योगिक सलाहकारिता भारतीय प्रौद्योगिकी संस्था खड़गपुर 721302 भारत ई-मेल: ipr @ sric.iitkgp.ernet.in |
संकायाध्यक्ष प्रायोजित शोध एवं औद्योगिक सलाहकारिता भारतीय प्रौद्योगिकी संस्था खड़गपुर 721302 भारत ई-मेल: deansr @ hijli.iitkgp.ernet.in |