inverter output current measurement

[attabros]

Hi Everyone,

I have designed an inverter I want to measure load current from. Output voltage is 220v AC. I want to read the current (I) measurement on analog bit of 16F877A.
What will be the best possible way? Kindly let me know the hardware section first.

Thanks

[Ttelmah]

Realistically, hall effect device. Search for a 'solid state current transformer'.
You then have to ask yourself what current you actually want to measure?. There is a big difference between the complexity of (for example), true RMS, with correction for power factor, or just the approximate delivered current from the system....

Best Wishes

[Guest]

Analog Devices has all sorts of nice power management chips that can help convert AC to DC for measurement with a PIC.

Also as suggested a hall effect device is nice, so are current sense transformers and even the lowly resistor.

There have been some clever design ideas posted on the EDN and Electronic Design websites (design ideas) that have to do with AC power measurement.

HTH - Steve H.

[FvM]

For a fixed frequency inverter, a current transformer is most likely the best solution (in contrast a variable frequency motor inverter must be expected to start near zero frequency, thus a DC capable current sensor would be required).

Because most CT have a low output voltage, a simple amplifier is required to drive the PIC analog input to full scale. The AC/DC and possibly RMS conversion can be performed in software, if some spare processing time is still available. Otherwise standard averaging rectifier or RMS circuits can be used.

[n-squared]

Question:
Since the power to the inverter comes from a DC source, can't we measure the current across a very low resistance power resistor and then calculate AC current?
_________________
Every solution has a problem.

[FvM]