EVAL-IH-R5IPB-A-V1 Evaluation board
User Guide
Experimental results
Figure 16 shows the experimental waveforms of the AC input voltage and the bus voltage, during a 2 kV surge
event, when the system is in stand-by mode, which means the current in the filter inductor is almost zero. As one
can notice, the input AC voltage reaches a peak value of 932 V, limited by the MOV, whilst the bus voltage (green
waveform) increases up to 824 V. For the given system, the worst case scenario is when the system is in operation
and a positive line-to-neutral surge occurs at a 90° angle of the input sinusoid, as the input AC voltage is at its
maximum, and the current into the filter inductor is also maximum (assuming a power factor close to 1). In the
latter case, the bus voltage can be even higher than the AC input voltage peak. Since the bus voltage increase is
much more significant than in the case presented in section 5.2.1, the effect on the collector-to-emitter voltage
of the IGBT is also much more significant. In this case, the single-level protection offered by current limitation of
the IEWS20R5135IPB may not be enough to avoid an excess increase of the VCE above the maximum permitted
limit of the device. Therefore, the additional protection offered by the over-voltage clamping feature
IEWS20R5135IPB reveals to be fundamental to properly protect the IGBT. Figure 17 shows the behavior of the
IEWS20R5135IPB during a 2 kV surge event. As soon as the surge occurs, the current of the IGBT (yellow curve)
increases faster and is eventually switched off by the over-current protection of the IEWS20R5135IPB. At IGBT
turn-off, the VCE increases (blue curve) and, due to the excessive energy injected by the surge, crosses the limiting
voltage threshold (which is set to roughly 1250 V), ultimately triggering the over-voltage mode of the
IEWS20R5135IPB. As a consequence, the IGBT is turned on shortly afterwards, and the collector current is
controlled in order to maintain the VCE to the selected threshold and prevent it from rising even further.
Application Note
24 of 34
V 1.1
2019-11-25