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In commissioning mode may be they only use current measurement, which has all the required circuits. I did not know yet if it is possible. But I am sure that the drives I looked at didn't have a voltage measurement circuit. They were 5.5 and 7.5 KW drives with different brands. May be some...
Mystery is this: Just focus on the DC-Bus voltage. All the drives are somehow measuring, using and displaying this info. But they have no -isolated or not- hardware(I mean direct or obvious voltage measurement hardware) for that purpose. So how can they extract this information? There are 3...
I think you misunderstood me. I will measure 2 voltages. One of them is DC. Harmonics or ripple are not important for that measurement. So an average value is OK which can be reached with a simple analog filter. The second voltage measurement won't be on motor phases during normal operation...
Why is the nyquist a problem? Every drive in the market works in similar conditions and their output frequency often exceeds 50 Hz and reaches upto 400Hz. Since IGBT switching frequency is limited to 20KHz, mostly they limit to 16KHz and the default value is generally 4-8KHz. My main concern is...
Ok. Electrical grid is 50 Hz. Motor frequency range is 0-50Hz. Inverter power will be 7.5KW. Switching frequency will be 4-16KHz. Pretty standart inverter circuit.
Think of 3-phase (400VAC phase to phase voltage) fed inverter system. Since Dc Bus is about 550-600VDC, I think isolation is required, am I wrong? There is a flyback transformer in the system with multiple outputs. May be I can manage to sense Dc Bus voltage somehow using one of the outputs...
The problem is cost. If I can eliminate two iso-amps from the circuit, then it will be better from the perspective of total cost. And pcb routing may be relaxed a little, because board area is tight and clearance and creepage rules are hard to follow in a tight area.
I used to use some kind of voltage sensor to make the isolated measurement of the voltage in a 3 phase inverter system. I've inspected several ac motor drives and I did not see any special IC like isolated amplifier or some sensor or a similar thing. I need to measure the DcBus and motor phase...
No, partly reducing is enough just to prevent damage from overheating. I estimate 150mA@24V will be drawn continously at max. But I want to add a 100-150mA extra room just in case to handle transients etc. It should folds back as soon as it exceeds 250mA to ~150mA or below and returns to normal...
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