European appliances in N.A.

I'm trying to determine if it is possible to import a European
induction cooktop (hob in U.K. terminology) to the U.S. The main
difficulty appears to be the 50Hz/60Hz difference. Not surprisingly,
the manufacturers say it won't work, but I don't know if that is the
truth or if that's just what the sales people are told to say in order
to protect the American sales channel (since they don't sell them here,
and the 2 manufacturers who do cover the U.S. market are prohibitively
expensive).

My questions are: how would one go about evaluating an appliance to
determine if it will work on 60Hz?

and, more for my own interest, what would prevent something from
functioning on a 60Hz power supply? I can understand motor problems
because of the way motors work, but I'm more than a little shaky on
electronic design. I'm assuming induction cookers work something like a
3000W audio amplifier (in very simplified terms), and therefore convert
the input power to DC, so I really don't understand why a small
frequency difference would cause so much trouble. Could have something
to do with high-efficiency power supplies?
Thanks for any information anyone can provide.

Colin Young

 

[x@nospam.com]

No. I'm looking for a lower-end model. Unfortunately, all the European
manufacturers are not making their induction cooktops available in N.A.
There are 2 that do: Diva de Provence, which has 2 models available for
$3000 and $4000 and AEG has I think 1 available for $3000. The Diva
models are manufactured by Die Deitrich (sp?) who also makes the Brandt
line, which I can obtain from New Zealand(!) for $1500 or $2000
depending on the model and including shipping and insurance. I'm pretty
sure that Diva is making a profit of at least $1000 on each model, if
not double that.

In the U.K., one can routinely find Bosch and Siemens induction
cooktops for Ł500 to Ł800, which comes in around $1000 to $1500. The
only difficulty is determining if it will work.

As I've stated, I don't know enough about how they work to even begin
to determine if the cycle difference will be an issue (they all use
cooling fans, but my understanding is that the motors would simply run
faster).

Colin

 

[x@nospam.com]

Thanks for the tip about Switzerland. The chart I was looking at didn't
list them as having 2 different frequencies.

I'll try giving that company in CA a call. Their site is a little
skimpy on info however.

I don't think the high frequency type are really all that complex. It's
just a 3kW amplifier driving a coil (and probably incorporating a
signal generator). I'm sure the details of the implementation are a bit
more complicated (after all, with a 7kW device at 85% efficiency you're
going to need to deal with about 1000W of waste heat, so I suspect most
of the complexity goes into getting the efficiency up to that level or
higher).

I'd still like to know why the mains frequency should make a difference
in this type of application. I'm assuming that all the internals will
be running DC up until a generated AC current is amplified to drive the
induction coils.

Thanks for the info.

Colin

 

[CWatters]

"x@nospam.com" <colin_young@yahoo.com> wrote in message
news:1107396923.072315.316430@g14g2000cwa.googlegroups.com...

Thanks for the tip about Switzerland. The chart I was looking at didn't
list them as having 2 different frequencies.

I'll try giving that company in CA a call. Their site is a little
skimpy on info however.

I don't think the high frequency type are really all that complex.

<snip>

I'm assuming that all the internals will be running DC up until a
generated AC current is amplified to drive the induction coils.

Yes my first thought was that they might rectify the incoming mains to make
DC then chop it up to make 22KHz - but then I wondered about the losses in
the rectifier. Probably too high for it to be a simple diode bridge. Would
they use a synchronous rectifier or some other method not involving DC at
all perhaps?

Any idea what the shipping costs would be on something as heavy as a hob? I
ask because I'm thinking of importing some bronze window frames from the USA
into the UK!

Colin

 

[x@nospam.com]

I have no idea... what's a synchronous rectifier (I have a guess, and
I'm going to do some research on the internet to find out)? The manuf.s
claim efficiencies of 75% (except for the sole American manuf. that
claims 90%), so I think the power supplies must be fairly efficient. I
don't know much about AC outside induction motors, so I can't even
begin to imagine how one would go about converting a 50Hz signal into a
20kHz+ signal to drive a coil.

It turns out the CA site you sent has a website that's 2+ years old and
they can't get those models anymore. There are models available that
operate on 50/60Hz but I don't know if that's a universal thing, or
specific to Brandt's line. I'm a bit reluctant to fork over $1000+ to
experiment (nor I am keen to have what I imagine as a "spectacular and
catastrophic" failure in my house, involving shooting arcs of
electricity and flying bits of shattered ceramic and molten metal,
although I do regard that outcome as an extreme longshot).

I think I need to either trick a manuf. into disclosing if it will work
on 60Hz supplies, or get in touch with a repair tech who knows how they
work. I'm not hopeful I'll have much success with either.

The shipping weight of a hob is 10-15kg and I've been told that
shipping and insurance would run about $150-200. Of course shipping
from the U.S. end may have different rates. I'm not sure if they would
exceed the dimensions for UPS or FedEx, but both sites have shipping
rate calculators online. There's also the option of a partial container
on a ship, and those costs are in the hundreds for bedroom furniture
from Java to Boston. I'm not sure where you'd go to get those rates.

Colin

 

[CWatters]

"x@nospam.com" <colin_young@yahoo.com> wrote in message
news:1107524137.251388.14600@g14g2000cwa.googlegroups.com...

I have no idea... what's a synchronous rectifier

An ordinary diode use the voltage polarity to switch itself on and off. A
synchronous rectifier uses a FET (or anothe active semiconductor device)
instead of a diode. However FETs conduct in both directions so some logic is
needed to switch the FET on for only part of the mains cycle. That switching
has to be synchronised to the mains hence the name. The advantage of using
a FET is that the voltage drop during the on phase can be lower than that of
a power diode.

I can't even
begin to imagine how one would go about converting a 50Hz signal into a
20kHz+ signal to drive a coil.

Much like a switch mode power supply in a PC.

I assume induction cook tops work like a step down transformer. The primary
winding is the cook top coil and the secondary is the bottom of the pan
itself. I'm not sure how they compensate for the variability in the type of
pan used (or even if they need to).

I think I need to either trick a manuf. into disclosing if it will work
on 60Hz supplies, or get in touch with a repair tech who knows how they
work. I'm not hopeful I'll have much success with either.

Good luck

The shipping weight of a hob is 10-15kg and I've been told that
shipping and insurance would run about $150-200. Of course shipping
from the U.S. end may have different rates. I'm not sure if they would
exceed the dimensions for UPS or FedEx, but both sites have shipping
rate calculators online.

Thanks I'll take a look.

Colin