transformer nameplate

[Sceadwian]

<removed redundant> or some such similar text infers this better.

 

[Reloadron]

In an effort to add some clarification or confusion attached are three images showing primary lead side and secondary lead side of a Stancor P-8662 Transformer. If we scroll down the data sheet we will see it as:

P-8662 117 24.0 C.T. 2.00 A Model P-8662, Primary Volts 117, Secondary Volts 24 C.T and Secondary Amps 2.00.

Also a basic pinout showing primary and C.T. secondary.

Now if we read the Basic Electrical Information General Specifications we will find the following:

Power Transformers

What is “VA” and its relation to “Watts”?
• VA is equal to the output voltage times the output current in
amps (VA = Volts x Amps)
• For the purpose of STANCOR’s catalog, VA and Watts are
typically equal.
What is “C.T.”?
• C.T. stands for Center Tapped
• This means that the transformer winding has an extra connection
(or tap) in the center. This provides the option to connect at this
point to achieve 50% of the rated voltage. This is also required
for a full-wave center tapped rectifier circuit.
• The typical transformer diagram below shows the primary input
on terminals/leads 1 and 2. The full rated secondary output is
obtained across terminals/leads 3 and 5. One half the rated voltage
at the rated current may be obtained from 4 to 3 or 4 to 5.
Terminal/lead 4 shows the location of the center tap. Some applications
may not require a center tap in which case it may
be insulated and not used.

What I believe may be of importance here is the data is for a specific transformer as specified by the people who wound it. Note what is said as to the secondary current. For that transformer it would lead one to believe if I want 12 volts using the C.T I can still have my 2 amps. However, if I choose to build a split supply of 12 volts I can only have 1 amp and 1 amp.

Ron

 

[wakoko79]

Great post Reloadron, it cleared up things. I think this particular post should be stickied in the Power supply design for begginers thread.

However, if I choose to build a split supply of 12 volts I can only have 1 amp and 1 amp.

Is that so? But my intuition tells me that it you can still have 2A and 2A for both rails. I think you are just tapping on one half of the windings one at a time, so the other half is not used when the other one is used so you can still do 2A for both rails. Am I getting it wrong?

 

[colin55]

Are you trying to create two separate 12v supplies from a 12v - 0v - -12v output?

If the CT consists of a loop, you need to break the loop.
If you can't the two supplies will be joined in the middle and each item you are supplying will need to be isolated.

If the transformer is 12v - 0v - -12v @ 2amp, each supply will be 2amp.

If the two projects cannot be isolated, the supplies will be +12v and -12v.

 

[wakoko79]

Are you trying to create two separate 12v supplies from a 12v - 0v - -12v output?

If the CT consists of a loop, you need to break the loop.
If you can't the two supplies will be joined in the middle and each item you are supplying will need to be isolated.

If the transformer is 12v - 0v - -12v @ 2amp, each supply will be 2amp.

If the two projects cannot be isolated, the supplies will be +12v and -12v.

No sir. I'm just trying to say what I had in mind about the post of Reloadron. Apparently we have the same idea about what he said.
I'm trying to build a 24V dc power supply.

Please visit this other thread I created:
https://www.electro-tech-online.com/threads/simple-linear-power-supply-design.126416/

Thanks=)