• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 47 subscribers
  • Views 658 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

AMC1350: How to connect for measuring line-to-line voltage?

mike buba
Intellectual 460 points
Part Number: AMC1350
Other Parts Discussed in Thread: AMC1351, AMC3330

Tool/software:

Hi All,

I am considering using AMC1350 (datasheet) for the three-phase AC line-to-line measurements. It has ±5V input, ideal for AC signals,

According to the recommended schematics from the datasheet, the GND is connected to the low side of the last resistor in the voltage divider, and the high-side VDD1 to GND1 should be max. 6.5V. The example in the datasheet is for measuring line-to-neutral (i.e., earthed), Figure 8-1.

But in my case (when connecting line-to-line voltage to measure motor output 400-690Vac), I have both lines at Vll/√(2) to ground, so in that way, my high-side VDD1 to GND1 will be more than 6.5V.

Is it possible to measure line-to-line voltage using AMC1350, and what would the connection circuit look like?

One more question: the figure below shows the input and output voltage range, where input is +/-5 V and output is +/-2 V. Is there any scaling in the block?

Kind regards, MB

  • 0
    TI__Expert 5380 points

    Hi MB,

    How are you planning to power the devices?  In the 3-Phase case, you will need a separate power supply for each phase.  You can take a look at this app note.  It's using a device with integrated DC-DC, but if you wanted to do the same measurements with the AMC1350, you would need a discrete solution to provide the supply.  

    It's a similar solution for the DC bus voltage measurement, you would need to derive the AMC1351's supply from the DC bus voltage and regulate it down to the correct range.  You can also look at this reference design.

    Thanks.

  • 0 in reply to Saleh Ahmad
    Intellectual 460 points

    Hi Saleh, Thank you very much for the reply. I read through the examples. In the reference design example, for the case of the AC votlage measurements, the high (hot) side GND1 is taken from the mid-point of the connection between the top and bottom IGBT of the half-bridge (0 V), and for the case of the DC measurements, GND1 is taken from the DC-, which I assume is also 0 V. 

    In my case, I am basically measuring the differential voltage. The app note shows something like that.

    Would you suggest using AMC3330 to measure differential voltage (unbalanced voltage and floating DC voltage, where GND1 is not at 0 V or grounded)?

  • 0 in reply to mike buba
    TI__Expert 5380 points

    Hi Mike,

    The AMC3330 would work if you don't have a supply already available to use.  Would you be able to send me your schematics for the above applications you are working on?

    Thanks.

  • 0 in reply to Saleh Ahmad
    Intellectual 460 points

    Hi Saleh,

    I have a situation like this (figure below), where neither P nor N are on the GND potential.Basically equivalent to measuring line-to-line voltage.

    Even with another power supply, if I use ACM1350, the INN input is connected to the GND input, and both are connected to the other power supply, GND. In my case, the INN input is not at 0 V to ground.

    This is the schematic I was thinking of using for AMC3330.

    Thanks, MB

  • 0 in reply to mike buba
    TI__Expert 5380 points

    Hi MB,

    A few things:

    - The voltage divider is currently sized so that around 500V across DC+/DC- would max out the inputs of the device.  Is 500V the max you would be expecting.  

    - The HLDO_IN seems to be shorted to the INN pin,  The INN pin and HGND should be connected together, close to the sense resistor.

    Thanks.