Very little, since the current transformer is a current output, which is not significantly affected by the diode forward voltage drop.
But make sure you add a diode to ground for the reverse half of the sinewave, otherwise you may blow the diode, along with possibly damaging the transformer.

Hi,

In theory yes, but toward the low end of the scale they are not as good.
Back in the 80's we used center tapped current transformers using two diodes for full wave rectification. There was a noticeable curve.
We could look into why this happens but it may be because the transformer acts a a voltage transformer at the low or a current transformer with limited voltage capability (similar to any real current source). Once we get above a certain value though it straightens out.
Oh it could be because of the core material that requires some minimum level of excitation. We might be able to model this using LT Spice.

Hey this thread is 11 months old

 

Hi,

In theory yes, but toward the low end of the scale they are not as good.
Back in the 80's we used center tapped current transformers using two diodes for full wave rectification. There was a noticeable curve.
We could look into why this happens but it may be because the transformer acts a a voltage transformer at the low or a current transformer with limited voltage capability (similar to any real current source). Once we get above a certain value though it straightens out.
Oh it could be because of the core material that requires some minimum level of excitation. We might be able to model this using LT Spice.

Hey this thread is 11 months old

This sounds similar to a problem I encountered a while ago with a current transformer-based measurement circuit which mostly worked, but with a small, non linear error.

In my case, it was suggested that the loss was due to primary magnetizing current, and that using a trans impedance amplifier would solve my problem. I don't understand transformers well enough to know if any of this translates to the current situation, but here's a link to that thread in case it's helpful:

https://forum.allaboutcircuits.com/...-to-dc-for-arduino.144283/page-2#post-1229518

 

If you have access to the noisy blower motor then it may also work to stick a pickup coil to the outside of the motor so that it will deliver a voltage when the motor is running. The coil should be on the side over a winding, not towards either end.. Of course, while you are that close to the motor you can look at the label and see if it has multiple speeds available. Selecting a lower speed will cut the noise way down, as well as saving power. So that is another option that you might have available. But be sure to switch off the furnace/AC power switch before working on changing the connection. And be sure to insulate the end of the high speed wire that you disconnect.

 

This sounds similar to a problem I encountered a while ago with a current transformer-based measurement circuit which mostly worked, but with a small, non linear error.

In my case, it was suggested that the loss was due to primary magnetizing current, and that using a trans impedance amplifier would solve my problem. I don't understand transformers well enough to know if any of this translates to the current situation, but here's a link to that thread in case it's helpful:

https://forum.allaboutcircuits.com/...-to-dc-for-arduino.144283/page-2#post-1229518

Hi,

Thanks, that was one of my guesses because magnetic cores dont work for free

But in our application back then it didnt matter because we used them as somewhat high current current limit functions, where if the AC load got too heavy the converter would start to cut back the synth sine pattern and thus limit the current to the load.
In that kind of application it only has to work at that one level which is the current limit level. Anything lower gets ignored anyway.

I should probably try to simulate that but dont want to do it right now.

Oh yeah also remember the excitation current waveform is very non sinusoidal too.