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High-resistance grounding (HRG) is preferred in many industrial applications where continual operation during ground fault conditions is critical. However, there are some drawbacks for the traditional HRG detection methods to locate a ground fault in adjustable speed drive systems. The existing methods cannot detect or identify which phase faulted once the drive has HRG fault. A leakage flux linkage detection-based method for HRG fault identification is proposed in this paper. It will be used to identify the faulted phase of the drive. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of voltage stress on the voltage insulation components inside a regenerative active-front-end adjustable speed drive (ASD). It shows that a high potential voltage insulation issue may exist on various components inside the ASD and cause earlier failures. A simplified system model to describe this phenomenon is described, and the voltage stresses of different components inside the ASD under different grounded conditions are analyzed. It is concluded that a much higher voltage stress may exist in different locations of the drive under different grounding systems. Appropriately designing the insulation components is critical to protect the drive. [ABSTRACT FROM AUTHOR]

The influences of PWM switching and long cable length on motor insulations have been discussed in numerous papers. This paper investigates their effect on the voltage insulation components inside an adjustable speed drive (ASD). This paper shows that high potential voltage insulation issue may exist on various components inside the ASD and cause earlier failures under very long cable or multiple drive conditions. A system model to describe this phenomenon is described in the paper. A dc bus voltage clamp circuit is proposed to reduce these voltage stresses. The effectiveness of this circuit is verified by both simulation and experimental results. [ABSTRACT FROM PUBLISHER]

Studies show that the power cycling mean time to failure (MTTF) of the insulated-gate bipolar transistor (IGBT) bond wire in an adjustable speed drive may be very short under some very common conditions. This paper proposes a switching frequency reduction method based on the junction temperature variation (\DeltaTj) of an inverter IGBT. It has the following advantages. First, it reduces the pulsewidth-modulation frequency under low-speed higher torque condition. Second, the inverter is started more smoothly and safely under higher command switching frequency and high-torque condition. Third, the overall MTTF of the inverter IGBT can be improved. The theory analysis, simulation, and experimental result are provided to show these advantages. [ABSTRACT FROM PUBLISHER]