Channel Oscilloscope Scope
How can I analyse 3 phase electricity on my oscilloscope without using current probes?
I was advised on a previous question to use 3 small step down transformers with resistor between phases (delta?) and connect secondary to "wye" for common ground. This is starting to make sense to me. Could someone please elaborate and maybe provide a website with schematics for this? Also, where would I find the materials for this project? Know of a good reference regarding analyses and balancing voltages of a rotary phase converter, preferably using an oscilloscope? I bought this Tektronix 2246 4 channel scope, I'll be darned if I don't use it soon. Thanks.
That was me, the no-lifer 8^)
No, no resistors needed, you simply place the primary of a transformer across phases A and B, a second transformer primary across B and C, and the third across C and A. DELTA. Then you tie one end of each of all three secondaries together, and that becomes your signal common. What you have just created is a 3-phase, delta primary, wye secondary transformer. It's a good idea to chassis-ground that point just so you don't get any unnerving but normally harmless sparks when you attach the ground leads of your scope probes to it. Then one scope probe to each of the other 3 ends of the secondaries. Nice and safe way to examine 3-phase voltages. The voltages you see will be the phase-to-phase voltage of the primary divided by the turns ration divided by the square root of 3. So, if your transformers are say 480V to 24V, and your input is 240 phase-to-phase, you should see
240/20/1.73 = 6.94 RMS (19.6 volts peak-to-peak) on the scope, referenced to the secondary wye common. Now do I get those 2 "Best Answers"?
8^)=
Email me if anything is unclear.
BW,
GH
[[[REPOST]]]
I just looked over my answer to your previous question, and yes, I did mention resistors, but they were for loading current transformers, which is what you use to examine 3-ph current. The answer above is for examining the voltages. Sorry for the confusion.
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