Stupid Question #1(more to follow) relating to transformers

[WB82]

Being I'm getting paid as an electrician I feel I should know the answer to this, and maybe I do, but just ain't seeing it???? Can the secondary of a transformer, be used as the primary instead?? Example, step up 110 source in to 220 out, can you have 220 source coming in on its labeled secondary side, with a 110 output on the labeled primary side?? Simple yes no, and brief explanation as to why or why not will be great..Thank you!

 

[Besoeker]

Being I'm getting paid as an electrician I feel I should know the answer to this, and maybe I do, but just ain't seeing it???? Can the secondary of a transformer, be used as the primary instead?? Example, step up 110 source in to 220 out, can you have 220 source coming in on its labeled secondary side, with a 110 output on the labeled primary side?? Simple yes no, and brief explanation as to why or why not will be great..Thank you!

You can use the transformer in reverse but not as you have described it.
If it is designed as a 220V to 110V step down unit, it will have a turns ratio of roughly* two to one. Feed 110V into the 110V (secondary) winding and you will get about 220V out on the 220V (primary) side.

*If the transformer was designed to give 110V on load, the turns ratio will be a bit less than 2:1 to compensate for voltage drop in the transformer. Thus, if you feed it with 110V on the 110V side, you will get a bit less than 220V out of the 220V side.

 

[WB82]

You can use the transformer in reverse but not as you have described it.
If it is designed as a 220V to 110V step down unit, it will have a turns ratio of roughly* two to one. Feed 110V into the 110V (secondary) winding and you will get about 220V out on the 220V (primary) side.

*If the transformer was designed to give 110V on load, the turns ratio will be a bit less than 2:1 to compensate for voltage drop in the transformer. Thus, if you feed it with 110V on the 110V side, you will get a bit less than 220V out of the 220V side.

Thank you sir

 

[augie47]

Here is a decent transformer tutorial:
http://www.acmepowerdist.com/products.asp?PAGE=prod_landing.html

(go to "Introduction" under "Dry Transformers")

 

[WB82]

Here is a decent transformer tutorial:
http://www.acmepowerdist.com/products.asp?PAGE=prod_landing.html

(go to "Introduction" under "Dry Transformers")

Thank you

 

[templdl]

You didn't state what the rating of the transformer was. As such I'll answer you questing in a general way.
Power transformers will have a given primary to secondary turns ration such as a transformer with a 240 pri. and a 120 sec. will have a turns ratio of 2:1. If you use that transformer as a step up applying 120 to the LV winding you will get 240v at the HV windings.
However, smaller MT (machine tool) transformers are not wound that way. You will find that the pri. of a 240/120 MT transformer will have fewer windings in the pri. than a simple 2:1 ration. What that means is that when 240v is applied to the pri. of an unloaded MT transformer 240v the secondary voltage will be higher than 120v. When a load is applied the secondary voltage will drop to a window of an acceptable voltage. If this transformer was designed with an exact 2:1 ratio as that of a power transformer then the sec. voltage would drop to a lower voltage than what is acceptable.
Bottom line is if you attempt to use an MT transformer as a step up transformer the voltage at the HV windings will be lower than that which would anticipate getting.

When a transformer winder winds the coils for a power transformer he will wind a specific amount of primary tuems bnased upon the primary and secondary voltages such a 480-120v would be 4:1.

 

[WB82]

You didn't state what the rating of the transformer was. As such I'll answer you questing in a general way.
Power transformers will have a given primary to secondary turns ration such as a transformer with a 240 pri. and a 120 sec. will have a turns ratio of 2:1. If you use that transformer as a step up applying 120 to the LV winding you will get 240v at the HV windings.
However, smaller MT (machine tool) transformers are not wound that way. You will find that the pri. of a 240/120 MT transformer will have fewer windings in the pri. than a simple 2:1 ration. What that means is that when 240v is applied to the pri. of an unloaded MT transformer 240v the secondary voltage will be higher than 120v. When a load is applied the secondary voltage will drop to a window of an acceptable voltage. If this transformer was designed with an exact 2:1 ratio as that of a power transformer then the sec. voltage would drop to a lower voltage than what is acceptable.
Bottom line is if you attempt to use an MT transformer as a step up transformer the voltage at the HV windings will be lower than that which would anticipate getting.

When a transformer winder winds the coils for a power transformer he will wind a specific amount of primary tuems bnased upon the primary and secondary voltages such a 480-120v would be 4:1.

Thanks