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analogsystemsrf
analogsystemsrf
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Do your control circuitry tolerate injected 6 volts, or 12 volts, atop any of the waveforms.

You should expect a 12 volt artifact imposed on any waveform, unless your probing methods are real-good, real low-area. Note this is at 4" distance.

And that high-frequency gate ringing? At 20MHz. What path supports that? For 20MHz, the LuhCpf is 25,330/(20 * 20) = 25,330/400 = 60 LuhCpf. At 10nH, C will be 6,000pF.

Years ago, I was asked to consult on a flawed speed controller for a rock crusher. Management/marketing wanted to improve the human-factors of the controlcab, and less room was available for the electronics (some installations will upgrade if "new" fits easily into "old" spaces in the rock plants.)

But the "new" had field failures. Occasionally. Turned out the embedded-system programmer had moved the control-electronics (for gate control of IGBTs) closer to the 500 amp (or was it 1,000 amps, or 2,000 amps bus-bar-plate) and some of the MOSFET drivers were failing, eventually). Some of the MOSFET drivers never failed, and some (positions on the PCB) were 80% of the failures. Thus we had a position-on-PCB-related field-failure situation. I used that same formula Vinduce = 2e-7 * Area/Distance * dI/dT to compute Vinduce.

In that situation, Vinduce was just a bit higher than 6 volts. I had the (local) field-rep craft a 25mm by 25mm (1" by 1") loop at end of coax, and go look for injected voltages. Couple weeks passed, and in the next phone-conversation, the consultant admitted he and the field-rep had seen/screen-grab voltages of 1.5 volts right against the PCB. I never knew whether the "against the PCB" was on the side-exposed-to-500ampere (2,000 amperes?) or on the side-shielded-by-PCB-chopped-up-planes.

How can 1.5 volts be a problem? Because 1.5 volts is right in the forbidden region for logic signals, and circuits are upset, with unknown state, when a metastable voltage appears.

You should expect a 12 volt artifact imposed on any waveform, unless your probing methods are real-good, real low-area. Note this is at 4" distance.

And that high-frequency gate ringing? At 20MHz. What path supports that? For 20MHz, the LuhCpf is 25,330/(20 * 20) = 25,330/400 = 60 LuhCpf. At 10nH, C will be 6,000pF.

Do your control circuitry tolerate injected 6 volts, or 12 volts, atop any of the waveforms.

You should expect a 12 volt artifact imposed on any waveform, unless your probing methods are real-good, real low-area. Note this is at 4" distance.

And that high-frequency gate ringing? At 20MHz. What path supports that? For 20MHz, the LuhCpf is 25,330/(20 * 20) = 25,330/400 = 60 LuhCpf. At 10nH, C will be 6,000pF.

Years ago, I was asked to consult on a flawed speed controller for a rock crusher. Management/marketing wanted to improve the human-factors of the controlcab, and less room was available for the electronics (some installations will upgrade if "new" fits easily into "old" spaces in the rock plants.)

But the "new" had field failures. Occasionally. Turned out the embedded-system programmer had moved the control-electronics (for gate control of IGBTs) closer to the 500 amp (or was it 1,000 amps, or 2,000 amps bus-bar-plate) and some of the MOSFET drivers were failing, eventually). Some of the MOSFET drivers never failed, and some (positions on the PCB) were 80% of the failures. Thus we had a position-on-PCB-related field-failure situation. I used that same formula Vinduce = 2e-7 * Area/Distance * dI/dT to compute Vinduce.

In that situation, Vinduce was just a bit higher than 6 volts. I had the (local) field-rep craft a 25mm by 25mm (1" by 1") loop at end of coax, and go look for injected voltages. Couple weeks passed, and in the next phone-conversation, the consultant admitted he and the field-rep had seen/screen-grab voltages of 1.5 volts right against the PCB. I never knew whether the "against the PCB" was on the side-exposed-to-500ampere (2,000 amperes?) or on the side-shielded-by-PCB-chopped-up-planes.

How can 1.5 volts be a problem? Because 1.5 volts is right in the forbidden region for logic signals, and circuits are upset, with unknown state, when a metastable voltage appears.

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analogsystemsrf
analogsystemsrf
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At 100 volts peak or 200volts PeakPeak, or 200/2.828 ~~ 60 volts RMS, for 600 watts you have 10amps RMS or 30 amps PeakPeak. The risetime of 100 nanoseconds provides a slewrate of 300 amps per microsecond. This produces intense magnetic field all around your PCB and +100v power leads (I see no bypass caps, to stabilize that +100 volts) and output "sin" waveform (through those 2 thick black wires running to the big capacitors).

Can you trust what the scope shows you?

Vinduce = [MUo * MUr * Area/(2 * pi * Distance)] * dI/dT

which we re-arrange to find

Vinduce = 2e-7 * Area/Distance * dI/dT

Now assume loop area is 0.1meter * 0.1 meter (4" by 4"); have lots of those in your circuit.

Assume distance is 0.1meter (either between wires and loops in your circuit, or between wires and the loop of your scopeprobe/GNDwire).

What voltage is induced? I don't know yet. We must run the numbers.

Vinduce = 2e-7 * 0.1m * 0.1m / 0.1m * 300 e+6

Vinduce = 2e-7 * 0.1 * 300 e+6 = 60 e-7 e+6 = 60e-1 = 6 volts.

Thus your current surges induce 6 volts into any 4" by 4" region of your PCB+wiring. Or perhaps 12v, because of "S" shape of typical risetime waveforms.

You should expect a 12 volt artifact imposed on any waveform, unless your probing methods are real-good, real low-area. Note this is at 4" distance.

And that high-frequency gate ringing? At 20MHz. What path supports that? For 20MHz, the LuhCpf is 25,330/(20 * 20) = 25,330/400 = 60 LuhCpf. At 10nH, C will be 6,000pF.