have there been significant improvements in enamel / transformer since 1970? - Page 1
Forum section: electronics / projects

author: CopperCone
author_rank: Super Contributor
timestamp: May 23, 2018, 03:55:01 am
content: I am curious because I am investigating the case of the Chinese variac.I read in another EEVblog thread that someone said their 8 amp variac basically weighs 25lbs, while a chinese variac rated for 20a also weighs 25lbs.Initially I thought that their just trying to sell shit, but I thought maybe there have been some improvements in enamel over the years? I mean I figure the chinese are still lying, but by how much is it being overrated?

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2018, 05:10:34 am
content: IIRC there were some improvements in transformer iron at some point in the 70s, and I think higher temperature enamels appeared too. I suspect the rest is a mix of cutting every corner they could in making the Chinese one while the original was likely over-engineered, and the ratings are likely a bit optimistic too.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 23, 2018, 05:23:23 am
content: The current rating is probably at 50% setting too, where an equal current flows in the winding, and the output current is double the input current. The rating drops to half this (equal to the wire's nominal rating) towards the ends of travel.Enamels have improved, though the time period is probably since the 40s or 50s, and 60s to 70s for higher temperature coatings. This coincides with going from varnish or enamel as such, to nylon and other artificial resins (with the development of solderable enamels), and polyimides (Kapton was introduced in the late 60s) applied to insulation, among other chemical advances.Tim

author: A Hellene
author_rank: Frequent Contributor
timestamp: May 23, 2018, 05:38:20 am
content: Well, as far as I know there have not been any innovations or breakthroughs in low frequency transformers, where, for example, the dominant practical rules for an E-I core transformer design are the following:P_out = 1.2 * P_in--We factor in a 20% (over)estimated power loss (due to core, resistance and capacitance losses); power efficiency can reach 90-95% in well constructed transformers. In toroidal transformers the estimated power loss factor becomes 15%, due to their lower stray magnetic field (no core discontinuities, gaps, holes and clamps).S = 1.2 * SQRT(P_out)--S: transformer core central leg cross section area, in cm^2N = 10^8 / (4.44 * B * S * f)--N: Number of turns per volt, B = 10,000 Gauss peak, f: operating frequencyOn the other hand, in toroidal core transformers the efficiency levels are somewhat better compared to (the properly constructed) E-I types, along with their ~50% lightweight core (because only the 'central leg' exists) for the same power.I can still remember, like it was yesterday, my early mentor in electronics telling me that'Watts and money are hard to be made'...Now, regarding the notoriously overestimated (and much 'cheaper')chineseWatts, what can I say?-George

author: Miyuki
author_rank: Frequent Contributor
timestamp: May 23, 2018, 10:02:48 am
content: Hmm ..Ultra-high temperature (600 ℃ above) inorganic ceramic magnet wire insulation was born in 1945 to 1950so old invention but prices of this product drop dramatically to this daysalso choke materials like Sendust and other have huge drop in price even in last few years or maybe just local distributors have better dealsall is long known but today these material are now cheaper than classic iron powder cores