Re: pole pig for sale

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

On 17 Feb 2005, at 16:27, Tesla list wrote:

> Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>
> At 10:31 AM 2/17/2005, Tesla list wrote:
> >Original poster: DRIEBEN@xxxxxxxxxxxxxxx
> >Christoph,
> >
> >Yes, you should be able to run a 60 hz rated
> >transformer on 50 hz with very little derating.
> >Many inductive (transformers, motors, ect) products
> >in the US are rated for their voltage/current at
> >50/60 hz, i.e. they will work on either frequency.
> >
> >David Rieben
>
> You can run it on 50 Hz with a 15-20% derating.  The inductive
> reactance is that much less, so, if, for instance, you have an ac
> motor (which typically don't have a huge design margin), to get the
> same winding current (which will be at lower HP, 5/6ths less, because
> the speed will be 5/6ths), you'll need to reduce the voltage by the
> same ratio. (This is what simple AC variable speed drives do.. they
> basically produce constant torque, but varying speed)
>
> For transformers, you're probably OK without derating, unless you're
> running at the ragged edge (which a pole pig isn't)...
>
> Just watch out for the 400Hz surplus transformers...

I sometimes repair US manufactured equipment which is supposedly
designed and rated for the NZ 50Hz 230V mains. Two notable features
stand out in the power transformers from one manufacturer in
particular: smallish cores and a rather high magnetizing current
together with, in some cases, substantial quiescent heating.

Malcolm