There are many advantages of using high frequency PWM (in the range of 50 to 100 kHz) in motor drive applications. High motor efficiency, fast control response, lower motor torque ripple, close to ideal sinusoidal motor current waveform, smaller filter size, lower cost filter, etc. are a few of the advantages. However, higher frequency PWM is also associated with severe voltage reflection and motor insulation breakdown issues at the motor terminals. If standard Si IGBT based inverters are employed, losses in the switches make it difficult to overcome significant drop in efficiency of converting electrical power to mechanical power. Work on SiC and GaN based inverter has progressed and variable frequency drives (VFDs) can now be operated efficiently at carrier frequencies in the 50 to 200 kHz range, using these devices. Using soft magnetic material, the overall efficiency of filtering can be improved. The switching characteristics of SiC and GaN devices are such that even at high switching frequency, the turn on and turn off losses are minimal. Hence, there is not much penalty in increasing the carrier frequency of the VFD. Losses in AC motors due to PWM waveform are significantly reduced. All the above features put together improves system efficiency. This paper presents results obtained on using a 6-in-1 GaN module for VFD application, operating at a carrier frequency of 100 kHz with an output sine wave filter. Experimental results show the improvement in motor efficiency and system efficiency on using a GaN based VFD in comparison to the standard Si IGBT based VFD.

SiC devices are gaining acceptance in the motor drive industry. This paper compares the power loss and efficiency between two options that can be used with SiC based Variable Frequency Drives (VFDs). In the first option, the SiC VFD is equipped with an output sine wave filter with carrier frequency at 50 kHz. A dv/dt filter is used for the second option with the carrier frequency reduced to 8 kHz. Both the options are compared with a standard Si IGBT VFD operating at a carrier frequency of 8 kHz with no output filter. The focus of the paper is to present different filtering options for SiC VFDs.The dv/dt filter is designed to meet the same specification as that of the standard Si IGBT VFD with no output filter, so as to present a fair comparison between a standard Si IGBT VFD and the next generation SiC VFD. Results using a 460V, 11kW system, show that the SiC VFD with output sine wave filter has lower efficiency compared to SiC VFD with a dv/dt filter. Influence of the various filtering options on leakage current in the motor drive system has also been studied and the results are presented in this paper.Index Terms: High-speed power semiconductor devices, Filtering options for high speed power switches, dv/dt filter for SiC VFD, Sine filter for SiC VFD, Efficiency comparison between SiC and Si-IGBT VFDs I. 0093-9994 (c)

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SiC devices are considered to be the next generation power device. This paper discusses thedesign of a Variable Frequency Drive (VFD) using a 6-in-1 power module that employs SiC-DMOSFETs and SiC Schottky Barrier Diodes (SBDs). A 400V class 11kW prototype drive is designed using a 1200V/50A SiC module by Cree. In this paper, power losses of SiC 6-in-1 module are measured and results are compared with an IGBT-based VFD. Analysis shows that SiC drive does not require current derating up to 60 kHz of PWM switching frequency while standard IGBT drive needs significant derating. High dv/dt and voltage reflection effects are important when fast switching devices like SiC are used. This paper explains the design of an optimal output filter.

SiC devices have received strong attention as the next generation power device. This paper compares the power loss and efficiency between two options that can be used with SiC based Variable Frequency Drives (VFDs). In the first option, the SiC based VFD is equipped with an output sine wave filter and the carrier frequency is 50 kHz. A dv/dt filter is used for the second option with the carrier frequency reduced to 8 kHz. Both the results are finally compared with a standard Si IGBT based VFD operating at a carrier frequency of 8 kHz with no output filter. The focus of the paper is to present different options to the drives industry in adopting SiC based VFDs which will soon become a standard product in the marketplace. The dv/dt filter is designed to meet the same specification as that of the standard Si IGBT based VFD with no output filter. This was deliberately done to present a fair comparison between a standard Si IGBT based VFD and the next generation SiC based VFD, from performance and loss points of view. A system rated at 460V, 11kW is used for all comparison tests. Results show that the SiC VFD with output sine wave filter has lower efficiency compared to SiC VFD with a dv/dt filter. Influence of the various filtering options on the leakage current in the motor drive system has also been studied and the results are presented in this paper. I.978-1-4799-5776-7/14/$31.00 ©2014 IEEE