Jun 7, 2011

A 110v surge protector instead of isolation transformers ?

I have been reading up a lot on step down transformers since I intend to get a Pioneer receiver from the US and am looking to see how to get a good deal.

Almost every thread on this in various forums has details on how to get the best transformer and more importantly, to get isolation type transformers. Comments like these abound : You need to get "Isolation Type" Step down Transformers. Now the reason given for getting a isolation type transformer is that the normal transformers can go bad and start supplying 240v directly instead of converting the voltage, thus bringing down the entire system.

Im thinking, how about getting a normal good brand (Maxine ?) transformer of 1kw/Rs 1k and take the output of the transformer into a US surge protector ($10) and then pass the output of the surge protector to the AV receiver. A good US surge protector comes with ample guarantees of coping with high voltages. So if the cheapo transformer does go bad and supplies more than 120v, the surge protector will kick in and protect the attached device.

Obviously, I could be missing something fundamental here in this line is thinking since folks spend 3-5k on isolation transformers. So Gurus, what am I missing here technically ? Can a surge protector NOT work with a transformer ? Any holes in the theory ?

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10 comments:

Anonymous said...

The receiver should also be able to run on 50Hz. A 60Hz only receiver will NOT run on 100v 50Hz. Many American versions of receivers such as Yamaha only run on 60Hz while the other region models run on 50/60 with appropriate voltage.

Vinayaga said...

Absolutely not true. I have plenty of folks who run their receivers from the US on a convertor. The receiver will run a little warmer than usual, that is all.

Anonymous said...
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Anonymous said...

That just means it's capable of running on 50Hz but not officially mentioned. If it's not, it'll blow up, quite literally. The transformer core inside the receiver will saturate and the entire input voltage (110v) will flow through the equipment.

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Vinayaga said...

Except for stuff that uses the frequency for clocks calibration, almost every component will work well with 50hz as it will with 60hz. I have bought bedroom clocks in the US which work real slow in India with a convertor. I have seen reports of US based receiver working a little more warm in India because of the frequency change, but nothing ever blows up because of that. If it blows, it is because of the voltage.

Anonymous said...

You don't know much about electricals. Foreign radio clocks run off AC without rectifying it, hence they run slow here. They are low power devices and it poses no hazard.

Its is only safe to run a transformer rated for low frequency on a higher frequency, not the other way around.

AC transformers can only handle current in short bursts, at rapid intervals. On a lower frequency the duration of each crest/trough is longer and this heats up the coil more than a higher frequency with shorter duration.

At low power output (low volume) the current is low, so the heating is minimal (as you've already noticed, they run hotter). When you crank up the volume, the current increases and the core will saturate and melt. There is very little physical separation between the two windings and they will short circuit and transfer the full input voltage to the device.

This is one of the advantage of isolation transforms. If the core saturates, there is no risk of short circuit.

Anonymous said...

You are just gambling on the fact that the transformer winding MIGHT withstand the longer bursts. There is a reason Yamaha labels their U.S. models as 60Hz ONLY, and other models as 50/60Hz. The U.S. model actually weighs almost 1kg less, since the winding is much thinner.

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