CCS/MSP430I2040: The EVM430-i2040S with the EMDC test questions

Hello Sam,

Thanks for your post.

yimin bai34 said:

1. Will there be a set of current offset settings can provide to adjust it after the EMDC of new version release?

No, the existing and upcoming release will not have current offset settings.

yimin bai34 said:

2. Does TI have the test report for EVM430-i2040S (for EMDC version)?

What test report are you referring to?

yimin bai34 said:

3. They consider to use the transformer to adjust the partial voltage for voltage channel, have any reference document about how to step by step to adjust it?

I'm not sure what you mean. The MSP430i2041 supports Current Transformers (CTs), although I don't know what you mean about partial voltage.

yimin bai34 said:

4. Will the new version EMDC can provide the fine tune function for AC frequency from 45~65 Hz?

The existing version (v1.20.00.00) allows users to accept AC frequencies from 40Hz to 70Hz. On the Advanced Parameters tab, you'll need to increase the IIR step size to maintain the resolution as the input range increases.

yimin bai34 said:

5. Is it must have the load when only calibrated the voltage?

Yes, you'll need to have both voltage and current applied to each phase during calibration of each phase.

yimin bai34 said:

6. Have the document to describe that how to calibration the phase step by step?

Yes, the calibration instructions can be found in the EMDC Technology Guide.

yimin bai34 said:

BTW, they still have the problem about the precision issue as below:

https://e2e.ti.com/support/microcontrollers/msp430/f/166/t/705378

I've provided detailed feedback that should address their issue. I suspect that they haven't tried my feedback.

Regards,

James

MSP Customer Applications

Bob Liao said:

We observed there were about 0.017A in no loading, but the actual current was 0A.

Why didn't EMDC have current offset settings ?

We did not see the need to implement current offsets in EMDC based on existing customer requirements/feedback and on our testing. I can add this to the list of requested features for future versions but can't promise it will get implemented. This can be done manually in the generated code if required.

Bob Liao said:

The meter measurement accuracy reports.

We are planning to update the User's Guides for the supported EVMs, and these reports will be included then. Due to other priorities, I don't have a specific date for this at the moment.

Bob Liao said:

PT is Potential Transformer, and it is used to transfer the voltage from a higher value to the lower value.

This should be fine, although EMDC can only support up to 1000V through the GUI. However, as long as the PT's output voltage stays within the FSR, you could scale the voltage accordingly. For the voltage sensor configuration in EMDC, I would just adjust the parameters for the (default) voltage divider to equal the maximum output voltage for your PT.

Bob Liao said:

What does AC Mains Frequency (Hz) affect in EMDC?

Note that this frequency influences some default parameters in the Advanced Parameters tab, specifically the IIR filter upper and lower limits. When you update AC Mains Frequency under the Basic Parameters tab, the other parameters under the Advanced Parameters tab automatically update.

Bob Liao said:

We only calibrated the voltage because the voltage value was dropped in heavy loading (e.g. 8A) and 8A was our calibrated point.

If the voltage and current are calibrated together, is the voltage accuracy OK ?

If your supply voltage is dropping at all when you're supplying 8A, then I would question the accuracy/capability of your source. Ideally, you want your source to be highly accurate for calibration. Otherwise, your results may be inaccurate. When you're calibrating through EMDC, you're changing both voltage and current scaling factors (and others) simultaneously. We did this to make the calibration one-touch (easier and quicker) rather than calibrating everything individually.

Bob Liao said:

Is the followings step to calibrate phase OK ?

1. Set calibrate voltage 220v, current 8A, and PF = -0.5(C.F.=3.5).
2. Click Phase in EMDC.
3. The voltage is 220v, current is 8.01A, and PF is -0.48 which were got from meter (CP-268).
4. Set VRMS(V) 220V, IRMS(A) 8.01A in EMDC
5. Set Phase Angle 118.68º which was got by converting PF -0.48 to cos angle in EMDC
6. Click Apply and Stop to save phase calibration values

This seems to be ok, although we use PF = 0.5 (+60 degrees). In Step 4, it's good that you're seeing the correct VRMS and IRMS. For Step 5, I'm not sure why you're setting the phase angle (of the source I assume) to 118.68 degrees. In Step 1, you set PF = -0.5, which is -60 degrees (we actually would use +300 degrees). Are you saying that in Step 5 you change from -60 degrees to +118.68 degrees during calibration? If so, I would recommend that you don't change the phase angle during calibration. After calibration is complete, please feel free to change it to whatever and view the results. I'm sorry if I'm misunderstanding you here.

Regards,

James

MSP Customer Applications

Hello Bob,

I apologize for the delayed response, and I'll do my best to answer your questions.

Bob Liao said:

1. Does “AC Mains Frequency (Hz)” ONLY affect IIR max and min frequency in EMDC advanced parameters ?

Basically, yes. The only other thing it affects is the nominal frequency used before the high voltage (HV) inputs are connected. This way, the measured frequency settles more quickly rather than assuming the lowest (40Hz) or highest (70Hz) possible frequency and then taking time to adjust from that value to the actual (close to nominal or expected) applied input frequency.

Bob Liao said:

2. Could we modify IIR min freq to 45hz, IIR max freq to 65hz, and IIR step size to 250 in EMDC for applying frequencies from 45Hz to 65Hz ?

If you know that the applied frequencies will be within 45Hz and 65Hz, then this will be fine. If there's a chance that the frequencies will be outside of this range, then I'd suggest using the range from 40Hz to 70Hz. Now, for the step size, the maximum is 250 steps. However, the IIR step size should really be odd. For a range of 45Hz (IIR min) to 65Hz (IIR max), this range equals 20 steps. Now, add 1 more to center the range limits around the nominal frequency. This equals 21 steps. So, instead of you choosing 250 steps, I would recommend using 249 steps. Otherwise, the frequencies in the generated lookup table get split into uneven values rather than whole frequencies. Be mindful that increasing the step size requires more Flash memory - 4 bytes for every step to be precise. Again, this is another reason we recommend using the i20x1 devices. You can hover your mouse over these parameters in the EMDC GUI to learn more about them or reference the EMDC Technology Guide.

Bob Liao said:

3. If we calibrate the EVM in 50 Hz, and is its measurement accurate in 60Hz or only accurate in 50Hz ?

During calibration, frequency is not adjusted. It uses zero-crossings with interpolation and the IIR lookup table. More importantly, the IIR range should include the expected AC mains frequency. As long as this is done, EMDC can accurately measure frequencies within that range.

Bob Liao said:

Should we set 60 degree or 61.314 degree if we set the loader as PF 0.5 and the real PF from meter(CP-268) is 0.48 ?

I'm not sure how accurate your "loader" is. If it's more accurate than your (comparison) meter, I would use it. If you're introducing PF 0.5 from the "loader", then I would assume it's providing PF 0.5 and would read what's shown in the Results tab in the EMDC GUI. My concern is that you don't know what's more accurate here, your "loader" or the comparison meter.

Regards,

James

MSP Customer Applications