Hi all,

Further to my recent question regarding recharging my shaver from a UPS
and the subsequent suggestion (amongst others) to get an inverter
instead, I decided that while the little ones were so cheap, I would
get one.

Trouble is, now i've bought it and had it delivered it has somethng
inthe instructions to say that it's not recommended to connect it to
shavers which connect directly to the mains for recharging as they can
be damaged by the inverters modified sine wave output.

This is a Statpower Powerbook 75i which is usually sold for powering
Laptops etc.


Does anyone have any ideas whether this would work ok with a Philishave
rechargeable razor, or any idea why it might damage said razor when
it's apparently ok for SMPSs and or wall wars driving low voltage
re-chargeable razors?

I can't see what could be different in the Philishave?

Most modern gadgets have switched mode power supplies, these should be
fine with modified sine waves.

Some equipment has linear (aka regulated) power supplies, these may not
like modified sine waves.

Generally linears have big transformers (and big capacitors) in them,
switchers smaller ones or none at all. But that isn't a guarantee.

The problem is the dc component in modified sine which causes an
excessive heating effect in linears.

You could try plugging it in and see whether it runs alarmingly hot.

wrote:

Most modern gadgets have switched mode power supplies, these should be
fine with modified sine waves.

Some equipment has linear (aka regulated) power supplies, these may not
like modified sine waves.

Generally linears have big transformers (and big capacitors) in them,
switchers smaller ones or none at all. But that isn't a guarantee.

The problem is the dc component in modified sine which causes an
excessive heating effect in linears.

You could try plugging it in and see whether it runs alarmingly hot.

Thanks for the explanation dom.

I did wonder whether it might either be excessive heat, or else
something making the device draw more current than it should.

Which bit of the Linears is is that doesn't like the DC?
Would running the inverter into an isolating transformer (shaver
socket) and connecting the shaver to the output of that be any better?

Which bit of the Linears is is that doesn't like the DC?

The transformer.

Would running the inverter into an isolating transformer (shaver
socket) and connecting the shaver to the output of that be any better?

No.

The problem is dc just make the transformer heat up, with no (easy)
solution available.

However I'd be surprised if recently manufactured rechargable
shavers use linear supplies, when everything else is using switchers.