[ask] calculating ampere in toroidal transformers - diyAudio
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Old 22nd September 2013, 07:29 PM   #1
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Default [ask] calculating ampere in toroidal transformers

hi guys,
i have a toroidal rated at 500watt
there are 4 output secondary:
0-48 0-48
0-36 0-36
0-24 0-24
0-18 0-18

assuming Watt=Volt x Ampere,
so if calculating from
48v > 500watt/2x48=5,2A
36v > 500watt/2x36=6,9A
24v > 500watt/2x24=10,4A
18v > 500watt/2x18=13,9A

does anyone know how to calculate properly?
i mean, what is the real current for 500watt toroidal transformer?
thanks.
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Old 22nd September 2013, 09:57 PM   #2
DF96 is offline DF96  England
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With multiple secondaries you can't tell, as there is no easy way of determining exactly how the designer apportioned his available VA among them. You may be able to get a rough idea by measuring their resistance - but measuring low resistances accurately is not easy.
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Old 22nd September 2013, 10:34 PM   #3
tinitus is offline tinitus  Europe
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I would say more likely like this (rough estimate)

0-48 0-48, 5A (x2)
0-36 0-36, 3A
0-24 0-24, 2A
0-18 0-18, 1A
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Old 22nd September 2013, 11:20 PM   #4
DUG is offline DUG  Canada
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Manufacturer?

Part number?

Picture?
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Old 23rd September 2013, 08:15 AM   #5
bountyh is offline bountyh  United States
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Quote:
Originally Posted by wengtech View Post
hi guys,
i have a toroidal rated at 500watt
there are 4 output secondary:
0-48 0-48
0-36 0-36
0-24 0-24
0-18 0-18

assuming Watt=Volt x Ampere,
so if calculating from
48v > 500watt/2x48=5,2A
36v > 500watt/2x36=6,9A
24v > 500watt/2x24=10,4A
18v > 500watt/2x18=13,9A

does anyone know how to calculate properly?
i mean, what is the real current for 500watt toroidal transformer?
thanks.
You are mixing Watts and Volt-Amps as if they were the same, they are certainly not. You must consider power factor. If you feed an AC winding into a full wave bridge, the DC load current available is only about 0.6 times the AC RMS current rating of the transformer secondary.


BTW:

Quote:
i have a toroidal rated at 500watt
Impossible. The transformer can not be rated in watts, it is V-A.
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Old 23rd September 2013, 08:48 AM   #6
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Electric power transformer is specified in VA (apparent power = volts X amps). Depending on the rectifier used, the DC power available is much less than the apparent power.

a) if the four windings of the transformer isn't separated galvanically, then winding rated current is calculated as follows:
I = Power / Voltage = 500 / (2 x 48) = 5.20 amps.
So, in such a case, all the windings of the transformer can be loaded with a maximum of 5.20 amps. To learn if the transformer is in this situation, you must measurement all sections winding conductors. If sections conductors are identical, then you are in this case, if not, see case b below.

b)
This case applies when the windings are galvanically separated. Measurement section conductors can provide us an idea about the current values ​​that can be charged by them, with the condition that relate to a certain current density (eg 3A/mmp). I can make you a concrete answer to this question but you need tell me the diameter of each winding conductor.
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Old 23rd September 2013, 11:19 AM   #7
AndrewT is offline AndrewT  Scotland
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Don is right.
You must check if there is:
one winding with lots of taps
or
two windings with lots of taps
or
many windings with no intermediate taps.

Can you see thickness of the wire in each tap and end?
This can be a good guide to current rating.
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Old 23rd September 2013, 11:57 AM   #8
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I agree with previous posts. check wether it is one winding with several taps or wether it is separate windings.

measure thickness to get an idea about current handling. forget about resistance measurment unless you have a low R meter.
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Old 23rd September 2013, 03:21 PM   #9
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hi... thanks for comment.
this is the sample pictures of toroidal i mean.

Click the image to open in full size.

this one rated 500W
with multiple secondary
diameter 14cm height 8cm
weight 4kg

what do you think.?
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Old 23rd September 2013, 03:41 PM   #10
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@wengtech, I asked you to tell us diameter wires, not the transformer size.
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