AMC1100: Delta Wired Voltage Measurement

Adrian Lavin84

Part Number: AMC1100

Can the AMC1100 be used to measure the voltage across the winding of a 3 phase induction motor when wired in Delta configuration i.e. there is no neutral point ?

Does the AMC1100 GND1 need to be referenced from any point on the windings or can it float with respect to the incoming voltage?

over 5 years ago

0 Alexander Smith over 5 years ago

TI__Mastermind 47625 points

Hello Adrian,

Thanks for your post and welcome to the forums!

To ensure that I am understanding this correctly, can you post a diagram of what you would like to do?

As I understand this question, you want to measure the difference between 2 phases using the AMC1100. This essentially creates a phase to phase fault with the differential input impedance of 28kOhm as the tie between phases.

The AMC1100 GND1 connection should be connected to the high-side ground.

This paper may help: www.ti.com/.../tidud07a.pdf

0 Adrian Lavin84 over 5 years ago

Prodigy 90 points

Hi Alexander,

Find attached the tina simulation for the design which seems to give a sensible output. I have a switch to simulate when GND1 is floating and when GND1 is the common reference for the line in voltages.

A3731.PhaseVoltage_AMC1100_.TSCdrian

0 Alexander Smith over 5 years ago in reply to Adrian Lavin84

TI__Mastermind 47625 points

Hello Adrian,

Thank you for providing the TINA schematic for my understanding.

From the way the schematic is drawn, I think there will be an input common mode violation with respect to your GND1 connection on the AMC1100. GND1 cannot float with respect to the incoming voltage. While the drop accross the R5 sense resistor may be within the VINP-VINN 250mV limit, GND1 will be significantly higher than 0V (the phase voltage) and the absolute max specs will be violated.

0 Adrian Lavin84 over 5 years ago in reply to Alexander Smith

Prodigy 90 points

Hi Alexander,

That was my feeling as well, I have found before this is where simulation can sometimes give false positives. Is it possible to update the AMC1100 tina model to account for this?

To minimise the common mode voltage issues do you recommend tying the GND1 to the ground reference for the line phase voltages V1phase0, V2phase-120, V3phase120?

Regards,

Adrian

0 Alexander Smith over 5 years ago in reply to Adrian Lavin84

TI__Mastermind 47625 points

Hi Adrian,

Yes indeed. I'm not sure what exactly causes that so I'll look into it.

Yes, the return supply of VDD1 should be tied at this point as well. Section 8 of the datasheet has schematic examples that may help for reference.

0 Adrian Lavin84 over 5 years ago in reply to Alexander Smith

Prodigy 90 points

Thanks Alex

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AMC1100: Delta Wired Voltage Measurement