Material properties for DIY generator - Page 1
Forum section: electronics / general

author: MrZwing
author_rank: Regular Contributor
timestamp: October 09, 2020, 11:15:09 am
content: HelloBeing the unendingly curious cucumber that i am i have thought a bout generators lately.So at my work i have noticed that one of the special alloys of steel we use have an extreme tendency to hold on to magnetic charge and orient itself to become magnetic in a way have haven't seen i any ferrite alloy to date. and thought about maybe experiment with generators or motors.So the question is where would a material that holds on to it magnetic properties for a long time most be suitable ( propably on the "magnet" part) but would the windings benefit or loose efficiency if it was wound around a material with a very slow "magnetic discharge" rate. in my mind if it holds on to its magnetic charge it could have a breaking effect but generators and induction is not something i read much about./MrZ

author: tom66
author_rank: Super Contributor
timestamp: October 09, 2020, 06:37:51 pm
content: There's not really such a thing as magnetic charge. I think you're describing magnetic coercivity, and there are materials that exhibit very high coercivity which retain their magnetic field long after being magnetised - these are used to make permanent magnets. Materials with high coercivity include iron, nickel and cobalt. Soft coercivity magnets are used to make ferrite cores in e.g. transformers and certain motors, as they can easily gain and lose a magnetic field with minimal loss and energy. I suspect what you're seeing is a steel that has a soft coercivity property; some forms of stainless steel are magnetisable. There's nothing much special about this but it's an interesting observation.

author: Cerebus
author_rank: Super Contributor
timestamp: October 09, 2020, 08:56:48 pm
content: Quote from: tom66 on October 09, 2020, 06:37:51 pmWell, if you use "charge" in the colloquial sense then there is a magnetic "charge" of sorts, remanence.

author: sandalcandal
author_rank: Unknown
timestamp: October 10, 2020, 08:13:05 am
content: As tom66 has explained, the terminology for what you seem to be describing is known as coercivity. High coercivity, i.e. the retention of magnetism without exposure to a separate magnetising field is generally undesirable as exposing the material to fluctuating magnetic fields (as would be the case in your suggested use as a generator winding core) results in undesirable loss of energy in the magnetic material in the form of heat i.e. piss poor efficiency. Low coercivity is desirable in materials used for power transformer cores or motor/generator winding cores but there can be trade-offs with other magnetic parameters.Higher coercivity and magnetically lossy materials do have uses however, in particular for applications where you specifically intend to lose energy as heat for example EMI filtering and inductive heating (not a required for inductive heating but it can help).Very high coercivity materials also do have their place in some electric motors as material for permanent magnets, as you've realised.It sounds like it might be helpful for you get a better grasp of magnetics basics. Applied Science has a good video introducing practical magnetics