WEBVTT

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The 24 VDC power supply controls a contactor via a pusher

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The continuous voltmeter is in parallel on the pusher (28 volts empty)

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In support of the voltage in the pusher is zero (0 V) but when I release ...

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Negative overvoltage is difficult to measure because it is very short but above 24 V!

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The surge is short car related to the stored energy

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When power is turned off, the coil tries to maintain the intensity and becomes the generator

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This has the effect of reversing the polarity of the voltage at its terminals

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With the attenuator, the LCD oscilloscope is on 400 Volts per vertical division

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The negative overvoltage was 3 divisions * 400 Volts = 1.2 kV

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The very violent reverse surge makes the oscilloscope 'crash'

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On the ground plane, no more worries EMC. The attenuated oscilloscope displays +/- 1,200 Volts maximum

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80 Volts * 20 (attenuator) = -1 600 Volts! (-1.6 kV)

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Another bug :-)!