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Joined: Jul 2001
Posts: 599
J
JBD Offline
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Treat the secondary of a "buck boost" no different than the secondary of a standard transformer. Make your intial calculations ignoring the fact you will use it as a buck boost. The amount the transformer can carry has to do with the way its low voltage windings are connected.

So a 500VA transformer with a 12/24V secondary wired for 24V has conductors rated to carry 20.83A.

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Joined: Oct 2000
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BigJohn;

Glad that we all were able to assist with the Buck/Boost Transformer sizing criteria.

As JBD described above, to figure the capacity of the Secondary Windings - in Amperes, divide the Transformer's rated Volt-Amps by the Secondary Voltage.

Using JBD's example Transformer above, these are the results:

500 VA Transformer - Secondary = 12/24V

* Secondary setup in Parallel for _12V_:
500 / 12 = 41.67 Amps maximum load Current through Transformer.

* Secondary setup in Series for _24V_:
500 / 24 = 20.84 Amps maximum load Current through Transformer.

Determine the "Per-Line" Amperes, which the Load Device will require, by dividing the Apparent Power (Volt-Amps) by the Voltage; or, if available, just use the nameplate Amperes of the Device.

If there is any doubt per these figures, feel free to reply as necessary! We are all here to assist.

Scott


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
Joined: Jun 2004
Posts: 1,273
T
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BJ...

Wire size, insulation rating, temperature rise...

Coil saturation at 60Hz normally never a concern.

Normally the designer spec'd small gauge high-temp conductors with insulation rated to 150 Centigrade. Even so, there's only so many amperes you can shove through the transformer.

This limit is found when the B-B is trying to bump/buck a lot of current a minimal voltage.

Normally this is no sweat since the typical B-B transform is 277 down to 240 ... or 208 up to 240. You do note that the RATIOS are the SAME. Stacking two such common B-B permits 277 to buck down to 208; which was a proposition on another thread.

------

Thus you have multiple limits: how much the magnetic circuit can handle and how much the conductors can handle. There are frequency limits, also, but at 60 Hz you not be troubled.


Tesla
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