Impact of Parasitics and Load Current on the Switching Transient Time and Motor Terminal Overvoltage in SiC-Based Drives

et al. 2021

IEEE Access

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The emergence of fast-switching wide-bandgap (GaN, SiC) power electronics devices has enabled motor drive systems to achieve high efficiency, power density, control bandwidth and high-level of integration. However, the fast-switching speed and high switching frequency result in an increased level of motor overvoltage at both motor terminals and stator neutral. This overvoltage increases the stress across the motor winding insulation and bearings. This paper investigates three types of motor overvoltages, i.e., differential mode (DM) (phase-to-phase) motor terminal overvoltage, common mode (CM) (phase-to-ground) motor terminal overvoltage and CM stator neutral overvoltage (motor neutral to ground). Both the high switching speed (high dv/dt) effect and the high switching frequency effect on the motor overvoltage are investigated in this paper, where the high switching frequency effect has not been fully addressed in existing literature. Significant overvoltage is observed when the switching frequency or its multiples coincide with the cable or motor anti-resonant frequency. The anti-resonant behavior in the cable and motor impedance has been used to identify the overvoltage oscillation frequency and to explain the overvoltage observations for the three types of motor overvoltages. The analysis has been tested using a 7.5kW motor setup with and without a four-core cable, driven by a SiC or a GaN three-phase inverter with a switching frequency up to 250kHz and switching speed up to 40kV/µs. In addition, the motor bearing current, which is a main cause of bearing degradation, has also been tested and the increase of bearing current is observed due to the high frequency effect.INDEX TERMS Anti-resonance, bearing currents, common-mode, differential mode, motor drive, motor overvoltage, neutral point voltage, gallium-nitride (GaN), silicon-carbide (SiC), switching frequency, switching speed, wide-bandgap.

Section: Peak = DC M + Dcmentioning

confidence: 99%

Section: Peak = DC M + Dcmentioning

confidence: 99%

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Impact of High Switching Speed and High Switching Frequency of Wide-Bandgap Motor Drives on Electric Machines

et al. 2021

IEEE Access

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“…Therefore, the conventional DPT, which only focuses on the rising edge of the output voltage, cannot be effectively used to address the RWP in three-phase inverter-fed motor drives. The above theoretical analysis has been experimentally verified in the authors' earlier conference paper [19].…”

Section: B Switching Transitions Of Line Voltages In a Three-phase Sic Invertermentioning

confidence: 56%

“…This article is based on an earlier conference paper [19] in which the authors addressed the impact of load current and device parasitic on the switching transitions of SiC-based twolevel power converters in cable-fed motor drives. This article summarizes the preliminary findings of the conference paper with further discussion, while extends the analysis to the Q3L T-type converter providing detailed reference to its operation, commutation process, and performance in mitigating the RWP in cable-fed drives.…”

Section: Introductionmentioning

confidence: 99%

Impact of Parasitic and Load Current on the Attenuation of Motor Terminal Overvoltage in SiC-Based Drives

Zhou

Diab

IEEE Trans. on Ind. Applicat.

2022

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In SiC-based adjustable speed drives, the high voltage slew rate (𝒅𝒗/𝒅𝒕) of the switching transitions results in excessive overvoltage at the motor terminals due to the reflected voltages across the drive power cables. Besides the cable length, the switching rise/fall times of the voltage pulses are a key parameter to quantify the motor overvoltage in PWM inverter-fed drives. These times are varying depending on the load current and parasitic elements of SiC MOSFETs, that is, a standard two-level converter typically results in a non-uniform overvoltage envelop at the motor terminals. This article analyses the switching mechanism of the two-level converter considering the impact of SiC parasitic elements and load current showing how they affect the motor overvoltage in cable-fed drives. The analysis is then extended to the mitigation of the motor overvoltage using quasithree-level (Q3L) modulation as a candidate filter-less approach with a T-type converter. The theoretical analysis is validated through experimental tests by using the Q3L T-type converter. The analysis and results show that the instantaneous load current value critically determines the peak motor overvoltage, while it allows either a full or partial overvoltage mitigation when the Q3L modulation is adopted.

Mitigation of Motor Overvoltage in SiC-Device-Based Drives using a Soft-Switching Inverter

Zhou

Diab

2020 IEEE Energy Conversion Congress and Exposition (ECCE)

2020

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In SiC motor drives, the high-voltage slew rate (/) of switching transients results in excessive motor overvoltage, due to the reflected wave phenomenon (RWP), which stands behind the premature failure of motor winding insulation while raises electromagnetic interference (EMI) problems. This paper adopts a soft-switching inverter topology, denoted as the auxiliary resonant commutated pole inverter (ARCPI), to mitigate the motor overvoltage caused by the RWP in SiC-based cable-fed drives. The performance of the SiC motor drive system under the RWP is first investigated to determine how the motor overvoltage is affected by the / of the inverter output voltage and the cable length. Then, a SiC ARCPI with profiled output voltage slew rate is utilized as a candidate solution to mitigate the RWP in the cable-fed motor drive. The effectiveness of the presented mitigation approach is experimentally verified, where it is shown that the ARCPI can completely eliminate the motor overvoltage and improve the EMI performance at high frequency region (500 kHz onwards) due to the prolonged rise/fall time of the output voltage, compared with the conventional hard-switching inverter. Keywords-Auxiliary resonant commutated pole inverter (ARCPI), high / , motor drives, reflected wave phenomenon, SiC MOSFET, soft-switching inverter.