Scott: One caution here is that the EUT load current in the secondary will induce a current in the primary which feeds through your amplifier output circuitry. There is a possibility of damage to the output circuitry due to induced voltage and current.
My experience in this area says to go conservative and low-tech. See if you can find an old McIntosh or Crown monophonic, VACUUM TUBE 100 Watt amplifier. A handy injection transformer (often seen in surplus) is the Solar 6220-1A (or -1 or -2). These are very gutsy, with lots of core steel. I wouldn't even bother with transformer ratios, etc. I would just use an FFT analyzer to watch my distortion levels in real time. Regards, Ed ------------------------ From: "Lacey,Scott" <[email protected]> Subject: Need Suggestions for Inducing Harmonic Distortion Date: Fri, 4 Dec 1998 13:23:31 -0500 To: "'[email protected]'" <[email protected]> > To the group, > > I am hoping that someone has some good suggestions for inducing harmonic > distortion > to the ac line input of an instrument under test. The nominal input is > 120Vac/60Hz. > The distortion frequencies are 120, 180, 240, and 300 Hz, at 5% applied > harmonic > distortion. > > The plan is to place the secondary winding of a 10:1 step-down transformer in > series > with one phase of the instrument under test. The distortion frequency will > feed the > primary of the transformer. Both frequencies will be generated by variable > frequency > ac sources. One source will be adjusted + or - 0.5Hz away from the exact > frequency > in order to explore all possible phase relationships over time. I plan to use > true rms > meters to monitor voltages. I also intend to first measure the open-circuit > secondary > voltage of the transformer in order to determine the exact winding ratio. > Another possible method might be to use a combination of 50 ohm attenuators > and > a splitter to sum the outputs of two oscillators into the external (50 ohm) > input of an > ac source. > My question is: > Will controlling voltage ratios be enough to guarantee 5% distortion, or must > I obtain > a distortion analyzer and actually measure the output? I hope one of the > group has > had some experience with this type of test. > This test can not be waived as the instrument being tested uses the ac > waveform as > a reference signal. > Thanks in advance for any help > Scott B. Lacey > [email protected] -------------------------- Ed Price [email protected] Electromagnetic Compatibility Lab Cubic Defense Systems San Diego, CA. USA 619-505-2780 List-Post: [email protected] Date: 12/04/1998 Time: 12:36:45 -------------------------- --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
