Ferrite or iron powder torroit with low temterature drift.

[asrock70]

My friend solves the following problém.
Needs to produce resonant transformer for 200kHz ultrasonic transducer.
L secondary 420uH 1:1 frequency 200kHz.
The tests used a toroid T50 material 77 Amidon.
The problem is, the material 77 has a temperature coefficient of 0.25 C / K and a transformer to operate in temperatures from -20 to +70 C.
Can you recommend any other suitable material for the manufacture of transformers with better thermal stability?

 

[smijesh]

N 27 From Epcos It will workout

 

[asrock70]

N27 have considerable dependence Initial permeability
versus temperature see Picture 2 on page 3

 

[FvM]

A reasonably designed resonant inductor would either use an air gap (ferrite core) or a low to medium pearmeability powder core, which has acceptable temperature drift.

 

[mtwieg]

FvM is correct. All ferrites are going to have large variation over such a wire operating temperature, the only thing you can really do is squash out the variation by lowering your effective permeability (use an air gap or a sparser mix). Or stabilize the temperature with oven control...

 

[asrock70]

Iron powder we proposed, but was told they are not suitable for transformers because powdered iron is not suitable for transformers, only inductors. It has a distributed air gap inside the core, and thus stores energy (ideal transformer must not store energy).
My idea will T50-3 or **broken link removed** maybe **broken link removed**, but low cost 26 probably not.
So how is it going Iron powder use or not?

Use something like **broken link removed** only for 200kHz cores are discussed in the last third