# Power step-up 200V->220V

Discussion in 'Electronic Basics' started by ChingChoke, Oct 27, 2003.

1. ### ChingChokeGuest

I wonder if anyone has a solution for this problem. I have move to
Rome, Italy where the power is 200V. In Italy the power ranges from
110-240, but in Rome it is, for some odd reason 200V.

Some of my UK appliances that I shipped over require 220V to operate.
200 won't do it. For example, the microwave will turn on but the
exhaust fan doesn't work and the unit seems underpowered; the Sony
radio/CD player doesn't do much more than light up, but no power.
There are a few other examples. (And some things run just fine;
scanner, coffee maker, etc.)

How can I step-up from 200V to 220-240V? I have seen step-up
transformers but they are always for 110-220 kind of thing.

Regards,
CC

2. ### Don TaylorGuest

EDN magazine (Electronic Design News) has a column in every week's
issue with cute little circuits that readers come up with.

A month or two ago someone had a circuit that used a ordinary 110-to-12
volt transformer wired up in a novel way to add the 12 volts to the
110 volts. The same idea could be used if you could find a 200-to-24
volt transformer or something similar.

They have a website and put up all the circuits so you could find
the site from their name and search to find the circuit.

3. ### Dimitrij KlingbeilGuest

Try using a step-down transformer 200V -> 30V. Connect the primary and the
secondary in series, apply the mains voltage (200V) to the primary, connect
the load to the pri+sec series (230V). Note that the transformer should be
able to handle the load current on the secondary. If the total load is
1200W (microwave), this means the current will be (for 230V) around 5.3 A
max. The transformer should thus handle 30V * 5.3A = 160W. You may want to
use a 200W transformer to have a little headspace in case the load will
increase (up to 1500W total load). Note also that power transformers
sometimes run hot, make sure the ventilation is adequate. If you connect
the secondary with the wrong polarity, the total output will be 200V - 30V
= 170V. In this case, reverse the secondary connection and everything
should work fine at 230V. The following table lists what transformers you
will need for some different total power consumptions.

Primary Voltage = 200V
Secondary Voltage = 30V

External Load (Max) Transformer Power (Min)

100W 15W
400W 55W
1000W 130W
1200W 160W
1500W 200W
2000W 260W
3000W 400W
4000W 520W

I hope, more power will not be needed, if not, use the calculation PT = PL /
230 * 30 with PT = transformer power and PL = load power. Multiple
transformers can be connected in parallel, but make sure their relative
polarities are correct (equal), otherwise the whole thing will burn up. Do
not forget a fuse (to be placed in the mains circuit before the primary).

Dimitrij

4. ### Michael A. TerrellGuest

A transformer configured as a boost converter isn't novel, its been
around for decades. That configuration, along with the buck converter
have been in print since I was a kid. The buck converter is used with
old radios designed when the line voltage was lower to prevent the
transformer from overheating from saturation.

5. ### petrus bitbyterGuest

Dimitrij,

The idea is good, but I'd look for a 220->24V or 230->28V transformer as
they are more common. They will do the same job however.

petrus.