Reading Continuity All Phases in Transformer
- #21
One last step the OP may well do is, in addition to continuity check, he may measure resistance also. The resistance may be small but not zero. Divide the applied voltage by the respective resistance. The resulting current may not exceed the OCPD rating provided.
- #22
If the OP is reading continuity through the transformer secondary, the resistance is certain to predict a current which exceeds the OCPD since it will be a source impedance rather than a load impedance and the %Z of the transformer will indicate a current many times greater than the design full load current.
- #23
Even the primary resistance will indicate a high current should be drawn.
- #24
So measuring just resistance only may not prove the system is sound, even though the resistance is not zero. So the OP may proceed with applying a low voltage consistent with the low resistance of the system. The system will draw a current. Divide the applied voltage by value of this current, the result being the impedance of the system.Now if the division of rated voltage of system by impedance results in a current not exceeding the OCPD rating, the system is probably OK. Otherwise, no.
- #25
Most of us will likely just check for ground faults on the primary and if none energize the thing.
Maybe if concerned about secondary you could lift the bonding jumper and check it for ground faults also.
- #26
Most of us will likely just check for ground faults on the primary and if none energize the thing.
Maybe if concerned about secondary you could lift the bonding jumper and check it for ground faults also.
I thought I described a general method including detecting ground faults.
- #27
I thought I described a general method including detecting ground faults.
You maybe did. Many of us aren't going to apply a low voltage though, that would require bringing another source to supply it with - and then of course we need to test it for faults before using it and an endless loop of testing before energizing....
- #28
You maybe did. Many of us aren't going to apply a low voltage though, that would require bringing another source to supply it with - and then of course we need to test it for faults before using it and an endless loop of testing before energizing....
The OP is not particularly concerned with detecting ground faults because phase to phase fault will not present as ground fault. So to convince him completely, my method is suitable. By the way, if OP has a working low voltage source, the infinite loop of testing the low voltage sources does not arise.:happyyes:
- #29
First we need to get him to understand why it is normal to have continuity where he though there shouldn't be any.
- #30
and he wonders if transformer secondary has continuity.. really? :huh:
Source: https://forums.mikeholt.com/threads/continuity-between-all-phases-neutral-and-ground.137669/page-2
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