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  • Author Author: three-phase
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3000A clamp table and amplifier update #2

three-phase

I have done some more work today on the current amplifier and found that I did not have the input turned up to a high enough voltage to obtain the full 1A output, so I have now repeated the test and monitored the heat output from the amplifier.

 

This is still just within the nominal operating temperature specified for the op-amp, but it was still climbing slowly when turned off. When switched back down to a 0.5A output, the temperature does start to drop away quite rapidly.

 

With this completed, I decided to do a few quick tests with a 20 turn coil and a CM55 current clamp as shown below.

 

{gallery} CM55 current clamp tests

10A reading expected on clamp meter

20A reading expected on clamp meter

Clamp meter taken beyond frequency specification

The first two tests show the clamp meter with the expected readings for a 50Hz input into the 20 turn coil. The frequency was then raised in the third picture and you can see that the current reading drops right off. For a Rogowski style clamp, the CM55 actually has quite a poor bandwidth.

 

My next stage with the current amplifier will be to try and figure out a way of measuring the input and output of the coils with the equipment I have, to see if there is any frequency drop off across the coil.

 

I have collected some impedance data for each of the coils I have wound using an LCR meter.

 

The data shows the increasing impedance of the coil as the frequency is increased. This may give issues with being able to reach the full output current using the existing amplifier design.

Anonymous
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  • Many thanks Gene. I did go and check the frequency response of the CM55 myself and it did surprise me how low it was. The older style tongue clamps did have a low frequency response due to the limitations of the magnetic circuit and the introduction of Rogowski coils provided a much higher frequency capability.

     

    The Fluke i2000 I have will go up to 20kHz, so it must be a design choice by Flir to reduce the frequency capability within the electronics.

     

    Kind regards.

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  • Many thanks Gene. I did go and check the frequency response of the CM55 myself and it did surprise me how low it was. The older style tongue clamps did have a low frequency response due to the limitations of the magnetic circuit and the introduction of Rogowski coils provided a much higher frequency capability.

     

    The Fluke i2000 I have will go up to 20kHz, so it must be a design choice by Flir to reduce the frequency capability within the electronics.

     

    Kind regards.

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