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 Post subject: Merit Coil & Transformer primary leads
PostPosted: Jan Tue 10, 2017 8:01 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 390
Location: Copake,NY
I just got a Merit Coil & Transformer power transformer.It appears to be NOS unless the leads have been changed.Heres my question.It has 2 seperate pairs of primary leads.One pair has one black and one red/black lead and the other has one white and one white/black lead.At first I thought it was one set for 120vac and one set for 220vac,but after testing it doesnt seem to be the case.Measuring the dc resistance,one measures 4.5 ohms and the other measures 4.0 ohms.When measuring voltage with no load the 5 volt and 6.3 secondaries measure the same with either primary connected.On the high volt secondary I get 400vac from the CT to one end with one primary connected and 401vac with the other primary connected.All voltage tests are with no load.What do you think is the purpose of these 2 sets of primary leads?Thanks in advance for any info.


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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Tue 10, 2017 8:41 pm 
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Location: Livermore, CA
The transformer was made to operate on 120 volts or 240 volts. For 120 volts both windings are to be wired in parallel. For 240 volt operation windings are to be wired in series.

You need to use both primary windings to get full current rating out of the transformer.

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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 1:59 am 
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Location: Copake,NY
Thanks,Norm.Does it matter how I connect in paralell?i.e. striped lead to striped lead,solid to solid?


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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 2:30 am 
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Location: Tucson, Arizona U.S.A.
stokes wrote:
Thanks,Norm.Does it matter how I connect in paralell?i.e. striped lead to striped lead,solid to solid?

Yes, it very much matters. If you don't have a data sheet to tell you the color code, try this. Connect one wire from each primary together and to one side of the AC line. Connect the other side of ONE of the primaries to the other side of the AC line. Measure the voltage between the free wire and the side of the AC line with only one wire connected. If the voltage is near 0, you have the right pair connected together; connect the other two wires together and you are good to go. On the other hand, if you measure 240 volts, reverse the connections to one of the primaries and try again. It should now be OK.

Or, here is another way. Connect both of the primaries in parallel, however you think might be right. Power the transformer through a dim bulb tester using a bulb of approximately the same wattage as the transformer or even somewhat smaller. If the bulb glows dimly, the primary connection is correct. If it glows brightly, reverse the connections to one primary and try again. It should now be OK.

If it doesn't work with either primary connection (whichever test you use), then there is some other problem.

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Jim Mueller


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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 3:09 am 
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Location: Maryland 20709, USA
Th striped primary leads should connect together, and the unstriped leads together, for 120v operation.

Wire it that way and check with a dim bulb tester as previously suggested.

On edit: Corrected a typo. The described wiring is for 120v operation.

- Leigh

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http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


Last edited by Leigh on Jan Wed 11, 2017 4:44 am, edited 1 time in total.

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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 4:03 am 
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Posts: 390
Location: Copake,NY
Leigh wrote:
Th striped primary leads should connect together, and the unstriped leads together, for 220v operation.

Wire it that way and check with a dim bulb tester as previously suggested.

- Leigh

That would be in parallel,no?Doesnt that contradict what Norm and Jim replied?


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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 4:10 am 
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Joined: May Tue 30, 2006 4:46 pm
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Location: Santa Rosa, CA
No...

Quote:
For 120 volts both windings are to be wired in parallel.


Rich


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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 4:31 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 390
Location: Copake,NY
Rich, W3HWJ wrote:
No...

Quote:
For 120 volts both windings are to be wired in parallel.


Rich

And what Leigh says is that parallel is for "220 operation"


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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 4:46 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Maryland 20709, USA
stokes wrote:
And what Leigh says is that parallel is for "220 operation"
That was a typo. I corrected it.

Parallel wiring is for 120v operation.

The other option would be 240v, not 220v as presented in that earlier post.

- Leigh

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73 de Leigh W3NLB
http://www.AtwaterKent.info
Click "Grebe Stuff" for Synchrophase info


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 Post subject: Re: Merit Coil & Transformer primary leads
PostPosted: Jan Wed 11, 2017 4:51 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 390
Location: Copake,NY
Oh,ok,it threw me off.


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