Transformer flux sensing

[bowman1710]

Hi guys,

I have a transformer that i want to sense the flux present over a period of time, what is the easiest way to go about this. I see that I can go down the hall effect sensor route, but im a bit unsure about how to go about it and whether it is something that i can even do without being to invasive with the transformer, also I see most sensors I could find have a maximum of around 500mT and I need to be looking at 1.5T to 2T. Any advice on which direction I could go or what my choices are likely to be, all help is much appreciated

Thanks

 

[c_mitra]

It is tricky because in a conventional transformer the flux lines are closed and no external sensor can be integrated at a later time. However, we can figure out the flux by looking at the leaking flux but I do not know how reliable will be the results. A Hall sensor placed closed to the core at a fixed distance perhaps can be useful. Alternatively, a secondary winding of 1-2 turns can be used to get an index of the flux in the core.

 

[Easy peasy]

you can glue bits of ferrite and a special hall sensor on the side of the core to measure core flux, must be away from DC or HF AC wires, we have done this for 50kW systems on UU90 cores, works well once you perfect the hall effect amplifier, shielding and geometry of the extra bits of ferrite

 

[bowman1710]

I was wondering whether I could use something like this to detect whether there is any remaining flux? Do you think this could work?

 

[Easy peasy]

How small amount of a remnant of flux density do you wish to measure?

 

[bowman1710]

Im a bit unsure of the amount, basically im having issues driving tape wound core with a primary current of 20A, 140V pk at 1.5Khz-20Khz, im trying to see if there is any remnant flux or there is a case of flux walking that is pushing the core into saturation? The core is a nanoperm tape wound core with Bsat of 1.2T. So i was looking at monitoring the transformer if at all possible.

Could i use something like this?

**broken link removed**

 

[Easy peasy]

easier to look at the current in the driven winding, this will tell you all you need to know...

 

[D.A.(Tony)Stewart]

Can you make a 50mV current shunt and scope current symmetry? especially harmonic content.
Saturation will reduce inductance, increase di/dt for the same voltage and be asymmetrical if there is remenance.

50mV/20A=2.5mΩ, a short pc. of wire calibrated.

using shielded twisted pair of magnet wire on the neutral side to a diff Amp with a split supply or bias up to V+/2 and nulled with a single supply.

 

[Easy peasy]

you need to research "peak current mode control"