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The transformer with its primary connected to the line and the the following waveform is what I get from the secondary.

transformer secondary Why is the waveform clipping, I suppose it is not in the primary side as I don't think that much clipping would go unnoticed. I have tested with another transformer and it is the same waveform.

Is the transformer core saturating? Whats the reason for the clipping?

PS: We have 50hz line voltage in India.

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  • \$\begingroup\$ Is your scope clipping? \$\endgroup\$
    – Dave
    Commented Dec 27, 2015 at 9:04
  • \$\begingroup\$ @Dave No, other waveforms with the save pk-pk voltage are fine. \$\endgroup\$ Commented Dec 27, 2015 at 9:07
  • \$\begingroup\$ Does it go away when you add a dummy resister load? Say 1000 ohms? \$\endgroup\$
    – Dave
    Commented Dec 27, 2015 at 9:09
  • \$\begingroup\$ @Dave No, nothing changes with load. \$\endgroup\$ Commented Dec 27, 2015 at 9:11
  • \$\begingroup\$ 51.Hz - is that a waveform from a portable generator? \$\endgroup\$ Commented Dec 27, 2015 at 9:12

2 Answers 2

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The transformer core gets saturated. You can use a variac to see if the clipping vanishes when you reduce the voltage. If this xformer is a toroid for hallogen lamp, then don't be surprised, if it is an industrial grade transformer then IMO you should send them back.

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  • \$\begingroup\$ But why would the voltage be, essentially, constant? Constant induced EMF = linear rate of change of flux \$\endgroup\$
    – Chu
    Commented Dec 27, 2015 at 14:43
  • \$\begingroup\$ @Chu How constant? What do you think that when the core gets saturated the induced voltage drops to zero? No way, there is still the inductance of the air core, and still the flux is rising, but with lower linear rate (with permaeabilty of air core). As you can see, the voltage is still rising - it is not cutoff in straight line. \$\endgroup\$ Commented Dec 27, 2015 at 20:22
  • \$\begingroup\$ Yes, my mistake, core saturation through overdriving does give rise to clipping. \$\endgroup\$
    – Chu
    Commented Dec 27, 2015 at 23:53
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Are you sure that's not an accurare representation of the actual line voltage?

line voltage can be truncated like that by rectifier-capacitor power supplies. Like the first stage of many switched-mode powersupplies, or those in traditional transformer-rectifier-capacitor DC powersupplies.

the trace you show looks like an extreme case, but not impossible.

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  • \$\begingroup\$ Maybe not, because I have tested it in a different location, and I am getting the same thing. And there is no smps or ups in the way either. \$\endgroup\$ Commented Dec 27, 2015 at 9:15

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