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Old 23rd February 2010, 01:14 PM   #31
bentl is offline bentl  Norway
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Hi Wachara!

You have some fancy equipment there! Stepper-motors and a control-card in a PC?


Regards
Bent
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Old 23rd February 2010, 01:18 PM   #32
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Hi Bent,

Yes, it uses stepper motors and is controlled by a computer.

Wachara C.
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Old 23rd February 2010, 01:28 PM   #33
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thanks for the tips jonas.is there an easier way to insert a new line with out having to hit the spacebar 1000's of times.also i do normaly use the forum window, but there have been times when i have lost hours of typing and had to start over.trying to remember everything can be quite difficult and very time consuming for such a simple task.you'd think that it could be recovered some how.but i haven't figured it out yet. cool winder, wachara!

Last edited by geraldfryjr; 23rd February 2010 at 01:32 PM.
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Old 23rd February 2010, 01:36 PM   #34
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also, it is confusing that the forum window is not the same size as the posts. as it looks good there but not after it has been posted. jer
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Old 23rd February 2010, 01:58 PM   #35
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Wachara, stepper motors are a nice way to avoid the need for a turns counter

Since you use 2 motors, do you have a way to control the wire tension as it's being wound?
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Old 23rd February 2010, 02:29 PM   #36
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Hi Kavermei,

I find it a lot easier to control the tension using my fingers.

Actually I have tried a few methods, but so far I have no success with a good tensioning device yet.

Wachara C.
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Old 23rd February 2010, 10:37 PM   #37
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Quote:
Originally Posted by geraldfryjr. View Post
Now here's little something that allot of people don't realize is that for every doubling of frequency the power rating is doubled and vice versa. So my 200watt transformer at 60hz now becomes a 400watt transformer at 120hz and so on.
My experience is that for every doubling of frequency the power a transformer can handle before core saturation increases by a factor of 4. Looking at the formula for Peak AC flux density this makes sense because the AC flux density is proportional to applied voltage, not power; and power is proportional to voltage squared.

Bmax = E x 10^8 / (4.44 x f x N x A)

Bmax = Peak AC flux density in core (Gauss)
f = frequency
N = number of primary turns
A = core area cm^2

Note that Bmax is inversely proportional to the number of primary turns.
Typical Bmax for modern transformer iron is about 12,000 gauss at the onset of saturation

Using a core area of 2.25 in^2 (14.5 cm^2) we can calculate core saturation levels for a range of frequencies.
I chose this core size because it is a fairly typical size used for full range transformers, and is probably pretty close to the core size of your toroidal power transformer.

Looking at the plot summaries for 60 turn and 10 turn primaries, you can quickly get an idea why you can't just reduce the primary turns to get a high step up ratio. As you reduce primary turns, the onset of core saturation comes at higher frequencies and lower voltage levels.
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File Type: gif Core_10.gif (91.0 KB, 607 views)
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Old 23rd February 2010, 11:46 PM   #38
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yes ,i understand this. which is why i was shocked to get the results i got with only 10 turns .i tried to send you an email through the forum did you receive it .it described my test procedure in detail? jer
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Old 24th February 2010, 06:46 PM   #39
bentl is offline bentl  Norway
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A quick question; should not a transformer be a 8ohm load on the primary side for the amplifier?

All spec's I have seen has stated 8ohms on the primary side.

regards
Bent
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Old 24th February 2010, 09:00 PM   #40
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Quote:
Originally Posted by bentl View Post
A quick question; should not a transformer be a 8ohm load on the primary side for the amplifier?

All spec's I have seen has stated 8ohms on the primary side.

regards
Bent
Hello Bent,

The quick answer is no. What ESL transformers have you seen specs for that state 8ohm?

For an ESL step up transformer the load impedance that the amplifier sees is a rather complicated function of the winding resistance and inductance, leakage inductance, winding capacitance, inter-winding capacitance, as well as the capacitive load of the ESL panel.

At low frequencies(below 500 Hz), the dominant parameters are primary winding resistance and inductance. At 0 Hz, the impedance would just be the winding resistance. As frequency increases, the primary inductance increases and thus the load impedance the amplifier sees. The higher the number of primary turns, the higher the inductance. The inductance is also a function of the permiability of the core which itself is a function of flux density(input voltage) and frequency.

At high frequencies(above 2kHz), the dominant parameters are leakage inductance, winding capacitance, inter-winding capacitance, and the capacitive load of the ESL. For typical ESL designs, impedance falls as frequency increases above 2kHz until you reach the resonant frequency between the leakage inductance and the sum of the capacitive loads. At resonance the impedance is usually quite low...less than 1 ohm. Beyond this resonance, the impedance rises again. Most ESL designs put a low value resistor(1 to 4 ohms) in series with the primary to damp this resonance.

Between these two frequency ranges, the impedance is rather high, usually peaking at 100 ohm or more.

The brief comments above are by no means a complete description of the parameters involved in ESL step up transformer design.
They are only meant give you an idea of how complicated the load impedance of an ESL and it's step up transformer are.
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