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Old 12th November 2005, 09:53 PM   #1
Alkis is offline Alkis  Greece
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Default HT transformers and polarity

Hi all,
Does anyone know,how I could find the right polarity of the AC mains connection on a HT transformer?
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Old 13th November 2005, 07:05 AM   #2
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AC mains doesn't have a polarity. It doesn't make any difference which way around you connect the transformer primary winding.

What AC mains does have is a live (active) and neutral wire. The neutral side is grounded at the power station but, by the time it gets to your home, it is usually a few volts live because of the voltage gradient along the power line. For that reason, a separate ground (earth) connection is usually provided as a third pin on the mains connector. You should ensure that the on/off switch and fuse are both in the live (active) wire if you can; alternatively, use a double-pole switch to disconnect both sides.
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Old 22nd November 2005, 12:58 PM   #3
Alkis is offline Alkis  Greece
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Hi Ray,
I think that we sould connect all the transformers in a device in a specific "polarity".This polarity is the one,inwhich the tester indicates some light on the secondary winding,even if we deal with a few volts.This is the maximum transportation of energy on a transformer.The manufacturers are aware of this principal and- in both cases-wire their products in the proper manner.
But as it concerns a HT transformer,things become more complex and I'm searching for an alternative.
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Old 22nd February 2006, 10:25 PM   #4
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Hi Alkis

are you talking about tens of kvs, just be careful, ac transmission levels are very dangerous

when you talk about polarity, the only polarity i see is winding
polarities

regards
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Old 14th March 2006, 12:40 PM   #5
Alkis is offline Alkis  Greece
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Hi Mastertech,I'm dealing with 1KV on a 845 project.I finaly found out a way to determine which side of the primary windings must connect to the live AC.
If we measure the AC voltage between the secondary windings and the third pole(ground) we get diferent numbers each time we alternate the connection.The right connection is the one that gives us the higher figers.The same test can occur on low tense transformers,where the higher figers make the tester light.
You may wonder,why all this?It is very possible that,this way we get a litle bit more power and a half of an octave deeper bass.
But after all,it's a matter of experimentation.
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Old 14th March 2006, 02:00 PM   #6
amperex is offline amperex  United States
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Default I do not discount anything

Perhaps listening to the transformer wired each way to the mains makes a difference. The reason I say such is some report a $100 or even $500 AC power cord makes the difference like a poor sounding GE preamp tube vs a Telefunken or Mullard 10M preamp tube. How a power cord can make that much diofference is beyond me. Perhaps some are 'BS'ing others- not sure.
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Old 14th March 2006, 04:46 PM   #7
kevinkr is offline kevinkr  United States
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Actually you should be measuring the leakage current between the primary, the core and/or secondary, you should select the orientation that produces the least voltage on the core of the transformer or secondary relative to a known earth ground. This is a also safety consideration should the safety ground fail or not be connnected.

This will also significantly reduce the leakage currents flowing through your chassis to the safety ground from your transformer core and should result in an electrically quieter unit as well.

Basically what I am saying is that good electrical practice would dictate finding the cold end of the transformer (closest to the core) and connecting that to the mains neutral.

From an audio perspective in 30yrs of tinkering I have never identified a difference in sound that did not relate to unwanted circulating ac leakage currents between components at different chassis potentials which is easily eliminated by following the above exercise whether or not a safety ground is used. (AND it should be)
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Old 14th March 2006, 06:10 PM   #8
Bazukaz is offline Bazukaz  Lithuania
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Default Re: I do not discount anything

Quote:
Originally posted by amperex
Perhaps listening to the transformer wired each way to the mains makes a difference. The reason I say such is some report a $100 or even $500 AC power cord makes the difference like a poor sounding GE preamp tube vs a Telefunken or Mullard 10M preamp tube. How a power cord can make that much diofference is beyond me. Perhaps some are 'BS'ing others- not sure.
About the power cords... We have hundreds of kilometers of HV cords from the power station ; than huge power transformers, than again kilometers of wire , than again transformers , and , finally , after a few killometers , it reaches our home.HOW can 1-2 metters of cable make ANY difference ?!
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Old 14th March 2006, 07:07 PM   #9
Alkis is offline Alkis  Greece
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But it's strange that the tester lights even after the tense is filltered(on a 12V psu for example).
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Old 14th March 2006, 07:21 PM   #10
Bazukaz is offline Bazukaz  Lithuania
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Quote:
Originally posted by Alkis
But it's strange that the tester lights even after the tense is filltered(on a 12V psu for example).
Transformer's capacitance may be sufficiently high to cause some current to flow.Lets say , we have a 2nF trafo's capacitance.At 50 Hz , its around 1.5 Megaohms reactance - you probably won't feel it , but tester can possibly detect this.
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