1. Cocchiara IT Session 1 – Block 1 – Question 3-1 Barcelona 12-15 May 2003 1 INVERTER OVER-CURRENT LIMIT OPERATION Output voltage reduction Output current below protection devices tripping threshold Output current is not enough to perform direct on-line induction motor start-up Inverter shut down

2. Cocchiara IT Session 1 – Block 1 – Question 3-1 Barcelona 12-15 May 2003 2 CURRENT PUMPING DEVICE (CPD) CPD INVERTERINVERTER LOADLOAD CONTROL To relieve inverter from over-load condition To increase current on the load

3. Cocchiara IT Session 1 – Block 1 – Question 3-1 Barcelona 12-15 May 2003 3 BENEFITS OF CPD INSERTION Short Circuit Polypropylene Capacitors Motor Start-Up Al-Electrolytic Capacitors 0.20.40.60.8 0 100 200 300 400 Upstream Downstream 0.20.611.41.8 0 500 1000 1500 2000 2500 time [s] Upstream Downstream Upstream 0.20.40.60.8 0 100 200 300 400 0.20.611.4 0 500 1000 1500 2000 2500 1.8 time [s] Downstream Upstream Downstream rms current [A]

4. Cocchiara IT Session 1 – Block 1 – Question 3-1 Barcelona 12-15 May 2003 4 SUPERCAPACITORS (EDLCs) FOR CPD REALIZATION High currents for extended periods of time Extremely small dimensions Capacitance of thousands Farads in very small devices Costs reduction in the next years

5. Cocchiara IT Session 1 – Block 1 – Question 3-1 Barcelona 12-15 May 2003 5 EDLCs DO NOT SEEM SUITED FOR CPD REALIZATION High ESR values (hundreds of m  up to 100  ) Small rated voltage values (about 2.3V) Capacitance is strongly dependent on frequency Current inverter side = Current load side 0.10.30.50.7 0 time [s] 200 150 50 250 100 rms current [A]

6. Cocchiara IT Session 1 – Block 1 – Question 3-1 Barcelona 12-15 May 2003 6 ESR reduction is desirable It is difficult to develop high voltage supercapacitors There is not a big market in AC applications: nowadays the efforts of the research are only oriented towards DC applications EDLCs DO NOT SEEM SUITED FOR CPD REALIZATION