Re: Current transformer compensation idea
From: mike (spamme0_at_juno.com)
Date: 07/28/04
- Next message: John Larkin: "Re: (Almost Idle Qu) How to Measure Complex Impedance?"
- Previous message: Cason: "Atmel IDE 8051"
- In reply to: analog: "Current transformer compensation idea"
- Next in thread: Dan Fraser: "Re: Current transformer compensation idea"
- Messages sorted by: [ date ] [ thread ]
Date: Wed, 28 Jul 2004 12:20:45 -0700
analog wrote:
> A typical current transformer may have a one turn primary and
> a hundred or more secondary turns. The secondary is normally
> terminated into a small resistor (possibly through diodes)
> such that the core must support a small ac flux excursion.
> With secondary signals in the volt range, the primary voltage
> burden is minimal, usually a few millivolts.
>
> Although dc drift may be a problem for some configurations,
> a typical current transformer rarely comes anywhere close to
> saturation during normal operation. In spite of this,
> inductive signal droop may be a problem in high fidelity
> applications (magnetizing current is typically very non
> linear).
>
> I have been toying with the idea of using active circuitry to
> minimize magnetizing current. My first idea was to arrange
> the current transformer to drive the summing junction of an
> opamp rather than terminating it into a small resistor. This
> would tend to keep the voltage across the CT's secondary at
> zero, which would be a noticeable improvement over the
> standard arrangement.
>
> However, this would still leave the voltage burden from the
> sense current flowing through the CT's winding resistance.
> Even this could be largely nulled out by actively driving the
> "grounded" end of the current transformer with a feed forward
> signal proportional to current appropriately scaled just to
> equal the drop developed on the internal winding resistance.
>
> Okay, I have never built this circuit and don't have a real
> application for it, but the simulator says all works great.
> What I am wondering is whether anyone has used or seen such
> a technique before or could imagine a situation where such a
> circuit might prove useful. Note that this technique does not
> eliminate the dc saturation problem (although it does make the
> CT's core "look" much bigger). Comments or further ideas?
>
> analog
Tektronix P6042 DC current probe.
Design from the '60s.
mike
-- Return address is VALID. Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121 Bunch of stuff For Sale and Wanted at the link below. HP200LX 10MB + MODEM + LEATHER CASE Sony Digital Camera Compaq Aero floppy,ram,battery. FT-212RH 2-meter 45W transceiver. Toshiba & Compaq LiIon Batteries, Test Equipment 30pS pulser, Tektronix Concept Books, spot welding head... http://www.geocities.com/SiliconValley/Monitor/4710/
- Next message: John Larkin: "Re: (Almost Idle Qu) How to Measure Complex Impedance?"
- Previous message: Cason: "Atmel IDE 8051"
- In reply to: analog: "Current transformer compensation idea"
- Next in thread: Dan Fraser: "Re: Current transformer compensation idea"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
