TIDA-01430: 3-phase isolated measurement?

Hi Adi,

Yes, it is possible to extend this to achieve 3-phase voltage and current measurement. There are multiple ways of implementing three phase measurement using shunt and voltage divider.
1. If you are using low side voltage measurement, you can club reference for the three phases together and provide isolation for shunt measurement. You can use multi-channel ADC for voltage measurement and isolate using ISOW7841 or similar model with higher number of channels.
2. You could also realize using high side voltage measurement and provide phase-to-phase isolation. This has been shown in TIDA-001472 using simultaneous sampled ADC ADS7250 (or ADS7850, ADS8350) and ISOW7842. Please refer to the design guide here: www.ti.com/.../TIDA-01472

ISOW7841 can be interfaced with any other Multi-channel ADC with the SPI interface. If there is a need for more than 4 digital lines, you could use additional ISO7840 or ISO7820 along with the ISOW784X.

Let me know if you have any further concerns.

Thanking you,
Prasanna

Hi Prassana,

In a case I want to achieve phase-to-phase isolation within CURRENT sensing and thus implement only 1 multichannel ADC for both, voltage and current measurement, I will not meet the requirement.
What are other drawbacks if just 1 ADC and 1 digital isolator are used in a system like this one?

Best regards,
Adi

Hi Adi,

There is no drawback of using just 1 ADC (with 8 differential inputs) and 1 digital isolator as long as you are able to interface 3-phase measurement to the input of ADC. Can you please provide more details on which configuration would you like to use for three voltage and current measurement?

Thanking you,
Prasanna

Hi Prassana,

I am implementing isolated 3-phase energy metering with requirements to have data storage up to one day, wireless and web browser as well (optional), accuracy for U and I measurement 0.2% (>12 bits of resolution). I would use MSP430FR5994 LaunchPad (16 MHz,12-bit ADC, SD slot built-in) with external 16-bit SAR ADC.

So, there are 2 posibilites:
1. Isolation amplifier per channel (AMC series) + external ADC + MSP
Current sensing : channel to channel isolation, Voltage sensing: input to output isolation
2. ADC + digital isolator + MPS

If I did not answer your previous question, please specify details about you are interested in.

Thank you,
Adi

Hi Adi,

I understand that you would like to measure three phase voltage and current using shunt and voltage divider. Thanks for the details of your system.
For the 2nd option in your previous message, my question was how would you like to configure shunts, voltage divider and ADC? My assumption was that you would like to use single ADC to measure all the 6 inputs.

Thanking you,
Prasanna U R

Yes Prassana, my first thought was to use single ADC for all inputs. How much it differs from the www.ti.com/.../TIDA-01472 regarding performance?

Best regards,
Adi

Hi Adi,

I am not sure how you are planning to measure three phase voltage and current using shunt and voltage divider using single ADC without isolating analog signals.
TIDA-01472 has similar performance as TIDA-01430 for V & I measurement, except that voltage and current in a phase is measured simultaneously. The selection between these two depends on performance requirement for phase angle measurement. For some applications, simultaneous sampling of V & I may not be necessary.

You may also have to look at specifications such as throughput requirement from ADC, number of SPI channels available on MSP and maximum clock frequency supported by MSP.

Thanking you,
Prasanna U R