DYNAMIC LOAD RESPONSE: As a result of the impressed inverter output wave form. Presenter: Dr Gawie van der Merwe

Copyright: Dr Gawie van der Merwe Introduction Single frequency inverters used for power conversion of 12 or 24V DC to 220V AC Output waveform varies between –Sine wave, Square wave, Modified Sine wave Various loads respond differently due to the voltage supply: –Examples: Single phase motors, fluorescent lights, computers, Microwave ovens, etc

Copyright: Dr Gawie van der Merwe Experimental setup Sine wave supply was generated using an Escom supply line. A H-Bridge inverter, with a varying DC link was used- to simulate square wave, and modified sinewave (refer sketch on next slide) Loads tested: –Fluorescent lights with electronic ballast –700W Drill –Single phase induction motor –Microwave oven OUTPUT VARIABLE DCLINK

Copyright: Dr Gawie van der Merwe Test circuit and supply voltages V250V275V310V Sine

Copyright: Dr Gawie van der Merwe Result: Difference between QS with Peak in area of 275V approx the same as sinewave- –Higher peak at 310V slower response notable QS Startup 100ms 80ms 60ms 140ms Current Peak A 18A 19 20A Running (RMS) 1.75A A Current THD % Value Square Sine 220V 250V 275V 310V 700W Drill

Copyright: Dr Gawie van der Merwe Electronic Ballast Sine waveCurrent Harmonic Content Current waveform with 220VCurrent Harmonic Content

Copyright: Dr Gawie van der Merwe Electronic Ballast 250VCurrent Harmonic content 310VCurrent Harmonic Content

Copyright: Dr Gawie van der Merwe Electronic Ballast Electronic Ballast load represents, most non linear loads, such as DC to DC converter, computers, etc An increase in THD of the current is noticeable QS inverter reduce lifetime of electronic ballast fluorescent lights

Copyright: Dr Gawie van der Merwe Lifetime reduction up to 60% Current peak of QS and Sine more or less the same Higher Harmonic content reduce capacitor lifetime Electronic Ballast

Copyright: Dr Gawie van der Merwe Single Phase Induction motor Very applicable application for fridges, borehole pumps etc. 310V DC link 250V DC link Sinewave 2sec 630 ms 240 ms peak 10,5A 275V DC link440 mspeak 9A peak 6,5A 220V DC link 580 mspeak 3,9A 9A Start up timeCurrent

Copyright: Dr Gawie van der Merwe Result Single phase motor warm up when run by QS With same load, power consumption varies Higher current peak

Copyright: Dr Gawie van der Merwe

Sine220V 250V275 V Comparative current harmonic content

Copyright: Dr Gawie van der Merwe Sinewave supply runs lights When power factor correcting capacitor is installed, no QS inverter will run lights To run fluorescent light, PF capacitor must be removed - non standard Magnetic Ballast Fluorescent Lights

Copyright: Dr Gawie van der Merwe Microwave Oven Typical requirement for farmers and mobile industry. –Water boiling test –1 Liter water

Copyright: Dr Gawie van der Merwe Microwave Oven Results Microwave Oven requires high voltage peak Energy transfer of sinewave supply up to 15% more effective Low QS wave form has no effect on working of microwave oven

Copyright: Dr Gawie van der Merwe Results & Conclusion A wide variation in dynamic response is visible Pure Sine wave is the best overall Fluorescent lights & Microwave ovens prefer higher voltage peak Motor warm up due to 3rd and 5th harmonic is visible Delayed single phase motor startup due to higher harmonics

Copyright: Dr Gawie van der Merwe Summary and future work The paper presented some load responses due to the impressed voltage wave form. It is clear that the applied wave form has a influence on the load. Lifetime reduction test are still being done.