Omg finally I know why airplanes use 400Hz, thank you! Honestly that's been on my mind for years.
=] On Wed, Jul 25, 2018 at 2:06 PM Carlos E Murillo-Sanchez via cctalk < cctalk@classiccmp.org> wrote: > Eric Smith via cctalk wrote: > > On Wed, Jul 25, 2018 at 7:54 AM, Paul Koning via cctalk < > > cctalk@classiccmp.org> wrote: > > > >>> On Jul 25, 2018, at 9:50 AM, GerardCJAT via cctech < > >> cct...@classiccmp.org> wrote: > >>> Why don't you simply power it through an inverter that will output 60 > >> Hz, eventually even "down to" 120 V , true sine wave, of course ??? They > >> are not that expensive by now. > >> > >> I wouldn't worry about "true sine wave". That seems more of a marketing > >> thing anyway, and motors don't care. Just feed them with a variable > >> frequency motor drive and all should be well. > >> > >>> And be carefull : motor designed for 60 Hz, running "under" 50 Hz, OR > >> THE OPPOSITE, I do not recall !!!, display a significant reduced life > time. > >>> I have to check which is which, but I know this is a question of > >> saturated magnetic field. Better check first. > >> > >> That doesn't sound right. If you run the frequency up high enough you > >> might get into problems with magnetic materials not designed for it. > And > >> much lower probably gives you reduced torque. But 50 vs. 60 Hz is a > >> trivial difference for a motor, I can't see any reasons for that to > cause > >> trouble. I routinely run my lathe at half frequency if not less, and it > >> doesn't complain. > >> > > I'm not sure about motors, but 60 Hz power transformers can't handle as > > high a maximum power (or current) when used for 50 Hz. The maximum power > > has to be derated. Some transformers are specified/sold with a single > power > > specification for both 50 and 60 Hz use, which just means that the vendor > > has built the necessary derating into even the 60 Hz specification. > > > > Some products were built using different transformers for 50 vs 60 Hz > > models, and the 60 Hz models uses a transformer inadequate for 50 Hz > > operation. > > > It has to do with the physics of flux linkages and saturation. Under > sinusoidal operation, voltage is proportional to the product of maximum > flux and frequency. If you fix the voltage, in order to operate at 5/6 > of the nominal frequency you need a flux that is 6/5 the nominal one. > This might not seem like much more flux, but due to the nonlinear > magnetization characteristics, the required magnetization current will > not be 6/5 times the nominal current, but it could in fact be three > times higher or even more, and highly distorted. > > Under-frequency and over-voltage can kill power transformers easily. > > A transformer designed to operate at 50 Hz will therefore have much more > iron mass in its core, power and voltage being equal. That's why in > airplanes power is distributed at 400Hz; the transformers will be much > lighter. > > carlos. > > > -- -- Anders Nelson +1 (517) 775-6129 www.erogear.com