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# Transformer amps

#### S-fr

##### Member
I would like to know the actual or at least the approximate amperage of this dual supply transformer thats is 25-0-25 12-0-12 i saw there was a chart thats was weight/amp, idk how good that is but my amp is like1.12 kg, anyway if there is anyway i can calculate it that would be helpful and I won't be using it as it is ill be combining the wires like 37-0-37 and use it like that

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One can estimate VA ratings usually by weight (IDK) but this doesn't look like a good candidate for audio speakers.
Maybe 10-20 VA. It doesn't look that useful without specs and known application.

The weight-to-amp chart you mentioned might provide an approximate guideline, but it's essential to note that this method might not be highly accurate.

To calculate the approximate amperage rating of your transformer, you can use a simple formula:

Amperage=Transformer Weight/Weight-to-Amp Ratio

As an example, if your transformer weighs 1.12 kg and you have a weight-to-amp ratio chart indicating, let's say, 0.5 kg per amp, you can estimate the amperage using the formula:

Amperage=1.12 kg/0.5 kg/A=2.24 A

weight-to-amp ratio chart

It would have to be weight to VA rating as Tony says - not weight to amps!

The core losses are rated in watts/kg for cold-rolled grain-oriented steel or CRGOS.

Here's a general example of specific power loss values for CRGO steel at 50 Hz for different thicknesses:

• Thickness: 0.23 mm
• Specific Power Loss: around 0.7 W/kg
• Thickness: 0.27 mm
• Specific Power Loss: around 0.9 W/kg
• Thickness: 0.30 mm
• Specific Power Loss: around 1.0 W/kg
• Thickness: 0.35 mm
• Specific Power Loss: around 1.2 W/kg
• Thickness: 0.50 mm
• Specific Power Loss: around 1.5 W/kg
• Thickness: 0.65 mm
• Specific Power Loss: around 1.8 W/kg
Please note that these values are approximate and can vary based on the specific grade and manufacturer of CRGO steel. The actual values for a particular application should be obtained from the manufacturer's datasheets or by contacting the manufacturer directly. Additionally, specific power loss tends to decrease as the frequency increases, so values may vary at different frequencies.

The core laminate efficiency is typically expressed as a percentage, and a higher stacking factor indicates a more efficient use of the core material.

Commonly, the stacking factor for transformer laminations falls in the range of 0.90 to 0.98.

The power density (PDPD) can be calculated using the formula:

PD=Specific Power Loss×FrequencyPD=Specific Power Loss×Frequency

where:

• Specific Power Loss is the power loss per unit weight of the core material (in W/kg),
• Frequency is the operating frequency of the transformer (in Hz).
In this case:

PD=1.2 W/kg×60 Hz=72 W/kg

So, the power density for CRGOS at 60 Hz, based on the assumed specific power loss, would be 72 W/kg.

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