RK05 spindle pulleys - trade 50Hz vs 60Hz?
anders.k.nelson at gmail.com
Thu Jul 26 07:26:17 CDT 2018
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 at classiccmp.org> wrote:
> Eric Smith via cctalk wrote:
> > On Wed, Jul 25, 2018 at 7:54 AM, Paul Koning via cctalk <
> > cctalk at classiccmp.org> wrote:
> >>> On Jul 25, 2018, at 9:50 AM, GerardCJAT via cctech <
> >> cctech at 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
> >>> 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.
> >> 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
> >> 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
> > 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
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