Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Remove Phase Lag of Voltage Transformer Output

Status
Not open for further replies.

shivakumar.r

Member level 1
Joined
Sep 5, 2011
Messages
39
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,601
Thanks For the suggestion..

I did experiment with small value of burden resistor(15ohm) and 470k input resistor for transformer.

Output voltage amplitude got reduced to 7mili volts rms.
And phase angle difference between input and output waveform is around 6degree.

I can use the internal programmable gain amplifier of ADC to amplify 7 mv signal to acceptable value.

Phase angle difference also looks reasonable.

I need to test the ckt with connecting to microcontroller and at different input voltages.

Mean while i will try out the other suggestions and check results.

Can i get some reference of
transformer with two secondary windings, or a tapped secondary.

More details about implemention of a zero flux circuit with separate source and sense to eliminates the winding resistance effect.

I can share this details with my transformer vendors.
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
49,392
Helped
14,437
Reputation
29,138
Reaction score
13,227
Trophy points
1,393
Location
Bochum, Germany
Activity points
284,272
See below three possible current transducer amplifiers with reduced phase error. Ltspice files attached.

First is the basic transimpedance amplifier configuration. Residual phase error is caused by transformer magnetizing inductance Lh, secondary winding resistance Rs and respective time constant Lh/Rs.

CT-Amp1.jpg

By using separate source and sense windings, you can achieve effectively zero phase error.

CT-Amp2.jpg

Alternatively you can compensate the windings resistance by adding positive feedback, creating a negative resistance. It's important that (R3||R4)/R5 must be always smaller than Rs/R2, otherwise the circuit becomes unstable. The circuit dimensioning must take into account both type variations and temperature dependency of the windings resistance (which is roughly proportional to absolute temperature). But it will achieve better results than the uncompensated circuit 1, even if calculated for large temperature range. Temperature compensation by PTC resistors is an additional option.

CT-Amp3.jpg

It's assumed that you want single 5V supply and 2.5V centered output. The OP can be any general purpose rail-to-rail amplifier.
 

Attachments

  • CT_amp1_3.zip
    2 KB · Views: 5
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top