Ian (G3AEK) said:
>Interesting figures... so the total weight of the transformer increases
>as something like the square of the core cross-sectional area. Seems
>about right.
>
>And then the capacity of a blower with an AC induction motor DEcreases
>with about the square of the mains frequency. It's small wonder that so
>much "50/60Hz" equipment is sweating when operated on 50Hz.
>
>I wonder how many developers in the 60Hz hemisphere actually have the
>capability to test equipment at significant power on 50Hz?
In mid 1980s the first model for a particular broadcast transmitter
that we built was to be sold to the Portuguese. It was for 50 Hz. So
we had iron designed for this, and we tested the entire system at
full power (only 5 kW RF thank goodness) in a 'heat tent' to make
sure that the unit could withstand the rated temperature at the lower
line frequency (blowers were slower, iron was hotter, ripple was
worse on the DC).
We rented a Catepillar Diesel generator, that could run 50 Hz, and
the smallest we could find was 100 kVA. So it ran for a weekend, and
coincidentally the Quincy, Illinois weather was deep snow and very
cold. The load was so light that the generator had trouble with
diesel gelling and ran rough, and we had to spend most of the time
working on keeping it going. The transmitter passed all the tests
though. Somewhere I have a photograph of myself in kneedeep snow,
next to this smoking diesel rig.
If gear is made to run on 50 and 60 Hz power, it should be tested at
both, to minimize Murphy's law from occuring!
John
K5PRO
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|