EXPERIMENTAL INVESTIGATION AND MEASUREMENT OF SHAFT VOLTAGE AND BEARING CURRENT IN 5-LEVEL INVERTER FED INDUCTION MOTOR DRIVE USING MICROCONTROLLER

摘要

The influence of different parameters of a variable speed drive system on the phenomena of inverter-induced bearing currents has been studied earlier under exactly the same conditions on inverter-operated A.C motor. Detailed modeling may not always be possible with practical Applications in the field, where many parameters might be unknown. Therefore, this paper presents experimental methods of measurement of the shaft voltage and bearing current for a modified 3- phase squirrel cage induction motor (IM) connected to a neutral point clamped (NPC) Inverter Bridge. Experiments have been carried out on 5-level inverter fed IM drives using space vector modulation (SVM) scheme. Microcontroller was used to generate SVM pulses along with other associated electronic interface circuits to operate the 5-level inverter bridge. Necessary converter circuits were fabricated and tested for giving the proper DC voltage supply voltage to the inverter bridge. Standard current probe, LISN and high frequency 4-channel Digital Signal Oscilloscope (DSO) with differential probes and were used to measure the shaft voltage, bearing currents other parameters. 4 Channel Mixed Signal Oscilloscope (MSO) was used to record the digital signals from the μcontroller. For comparing the results with Federal Communications Commission (FCC) and Special Committee on Radio Interference (CISPR) standard, graphs were plotted showing Frequency vs shaft voltage in dBμV and the bearing current in dBμA using the signal analysis software and compared with the 3- level and 2-level inverter IM drive results.