Transformer testing

[atec77]

I have in 50 ac tranny@ 40 amps , it's unmarked but is 240 primary
however how to id windings , any suggestions as of course I wont be
just plugging stuff in , ex telecomms
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[Rheilly Phoull]

On 5/18/2011 12:43 PM, atec77 wrote:

I have in 50 ac tranny@ 40 amps , it's unmarked but is 240 primary
however how to id windings , any suggestions as of course I wont be just
plugging stuff in , ex telecomms

Well the dc resistance of the primary would be much higher than the
secondary for starters. If there are taps on the primary it should be
easy to identify the highest resistance pair to start off with and
experiment with since if it's 415v you wont be doing any harm by hooking
that up to 230v.

 

[Phil Allison]

"Rheilly Phoull"

I have in 50 ac tranny@ 40 amps , it's unmarked but is 240 primary
however how to id windings , any suggestions as of course I wont be just
plugging stuff in , ex telecomms

Well the dc resistance of the primary would be much higher than the
secondary for starters. If there are taps on the primary it should be
easy to identify the highest resistance pair to start off with and
experiment with since if it's 415v you wont be doing any harm by hooking
that up to 230v.

** For a 230 VAC primary - expect 0.5 ohms

For the 50VAC secondary - expect 22 milliohms

A "soft start" circuit will be needed for sure - or it will trip the
breaker as soon as you switch it on.


...... Phil

 

[Rheilly Phoull]

On 5/18/2011 1:18 PM, Phil Allison wrote:

"Rheilly Phoull"

I have in 50 ac tranny@ 40 amps , it's unmarked but is 240 primary
however how to id windings , any suggestions as of course I wont be just
plugging stuff in , ex telecomms

Well the dc resistance of the primary would be much higher than the
secondary for starters. If there are taps on the primary it should be
easy to identify the highest resistance pair to start off with and
experiment with since if it's 415v you wont be doing any harm by hooking
that up to 230v.


** For a 230 VAC primary - expect 0.5 ohms

For the 50VAC secondary - expect 22 milliohms

A "soft start" circuit will be needed for sure - or it will trip the
breaker as soon as you switch it on.


..... Phil



Like you say

What do you reckon to a 30R 100W with a switch across it ??

 

[Phil Allison]

"Rheilly Phoull"
Phil Allison wrote:

** For a 230 VAC primary - expect 0.5 ohms

For the 50VAC secondary - expect 22 milliohms

A "soft start" circuit will be needed for sure - or it will trip the
breaker as soon as you switch it on.


Like you say

What do you reckon to a 30R 100W with a switch across it ??

** Depends if the PSU has to come up while under load or not.

If it does, then a couple of chunky 15 amp rated, 2 ohm NTC thermistors are
the go.


..... Phil

 

[atec77]

On 18/05/2011 7:02 PM, Rheilly Phoull wrote:

On 5/18/2011 1:18 PM, Phil Allison wrote:
"Rheilly Phoull"

I have in 50 ac tranny@ 40 amps , it's unmarked but is 240 primary
however how to id windings , any suggestions as of course I wont be
just
plugging stuff in , ex telecomms

Well the dc resistance of the primary would be much higher than the
secondary for starters. If there are taps on the primary it should be
easy to identify the highest resistance pair to start off with and
experiment with since if it's 415v you wont be doing any harm by hooking
that up to 230v.


** For a 230 VAC primary - expect 0.5 ohms

For the 50VAC secondary - expect 22 milliohms

A "soft start" circuit will be needed for sure - or it will trip the
breaker as soon as you switch it on.


..... Phil



Like you say
What do you reckon to a 30R 100W with a switch across it ??
I took a quick measurement and then excited the secondary with 10 v ac ,

soon worked out the correct primary taps to arrive at the desired 24vac out

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