Say I have a SE OPT with a reflected 8k primary impedance rated 50mA DC which happens to have a CT at 2K.
Because saturation goes with amp*turns it should be possible to use the half primary as a 2k OPT but at double the DC (100mA) without ill effects.
To restore the primary / secondary interleaving winding structure and the current capacity it might be beneficial to cut the wire loop at the CT and parallel connect both half primary windings, properly phased of course.
Anything wrong with this ?
Because saturation goes with amp*turns it should be possible to use the half primary as a 2k OPT but at double the DC (100mA) without ill effects.
To restore the primary / secondary interleaving winding structure and the current capacity it might be beneficial to cut the wire loop at the CT and parallel connect both half primary windings, properly phased of course.
Anything wrong with this ?
I agree paralleling the two primary winding sounds like a good idea, it might pay to examine the windings to see it there will not be an insulation problem when the windings are phased correctly, both wires to the 2k tap were originally at the same potential, when re-phased for a 2k primary this will not be so. I would also feed the secondary from a signal generator and confirm both the primary windings have the identical number of turns, a few turns out made no difference when the tap was used as a screen tap it will however affect performance if the windings are paralleled.
Regards Ken K
Regards Ken K
Like Ken said, you definitely need to verify the equality of turns of the sectors you'll be paralleling first. And yes, check insulation. Although voltage breakdown requirements for 2k pri impedance will be lower for the same power (lower primary voltage swing).
If you get different voltage readings from expectedly equal coils, also suspect equipment. I found out some DMMs with some generators for some reason give inexistent winding disbalances. To check for equipment problems, it's a good idea to reverse coil connections and measure again. If the disbalance ***** with polarity reversal, then equipment can be suspected.
Otherwise it's pretty safe to parallel primaries. Parasitics will change also. You can expect capacitance to nearly quadruple, leakage to decrease inversely.
If you get different voltage readings from expectedly equal coils, also suspect equipment. I found out some DMMs with some generators for some reason give inexistent winding disbalances. To check for equipment problems, it's a good idea to reverse coil connections and measure again. If the disbalance ***** with polarity reversal, then equipment can be suspected.
Otherwise it's pretty safe to parallel primaries. Parasitics will change also. You can expect capacitance to nearly quadruple, leakage to decrease inversely.
Primary's parasitic capacitance will quadruple with parallel windings. But on the positive side, leakage inductance will decrease 4 times. Transformer's self-resonance frequency will remain unchanged.
Purposely made 2 K transformer with the same core and interleaving structure will have 1/4 of winding capacitance of the modified 8 K transformer, and thus much higher self-resonance frequency.
Purposely made 2 K transformer with the same core and interleaving structure will have 1/4 of winding capacitance of the modified 8 K transformer, and thus much higher self-resonance frequency.
Thank you for comments.
It just occured to me that primary inductance will also be down 1/4. Might be the bigger disadvantage ...
It just occured to me that primary inductance will also be down 1/4. Might be the bigger disadvantage ...
All the above comments seem correct; the advantages, disadvantages, and things to watch out for.
The worst thing to do is to leave 1/2 of the primary winding disconnected.
It makes a terrible resonator, badly affecting the phase, frequency response, and square wave response of the transformer.
I say this just for any newbies who have a single ended 8k transformer with a UL tap, and want to use it at its full winding rated current, but they want the lower impedance of 1/2 of the primary.
The worst thing to do is to leave 1/2 of the primary winding disconnected.
It makes a terrible resonator, badly affecting the phase, frequency response, and square wave response of the transformer.
I say this just for any newbies who have a single ended 8k transformer with a UL tap, and want to use it at its full winding rated current, but they want the lower impedance of 1/2 of the primary.
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