| Electronics > Beginners |
| Testing AC currents |
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| Aggressive_Doughnut:
I have a CT rated for 30A and wanted to test it at around 10A (15A circuit breakers on a nominal 120V line). I can use a variac to make the voltage more palatable, but I'm not sure how to get the 10A safely/cheaply/easily. Should I just invest in a bunch of 50W chassis resistors and parallel them together? |
| Gregg:
Current transformers only measure the current; therefore if you run the test power through a low voltage / high current transformer you won’t need a lot of power converting to heat for your experiment. Enclosed are some pictures of an old school Weller soldering gun with wire attached instead of the heating tip. These solder guns are basically a transformer with a single turn for the low voltage / high current that is short circuited at the tip which is higher resistance than the rest of the single loop. Here I have used several turns to increase the current that the CT sees and I have used two parallel wires to handle the current. The magnetics of the Weller heat gun are designed to saturate at full short which magnetically limits the current to not damage it. You could use a Variac ahead of the primary of any suitable low voltage transformer to vary the voltage which in turn varies the current (ohms law) and wrap more than one wrap of the secondary around your CT. If you want to check circuit breakers, look at what people have done to convert microwave oven transformers into spot welders. |
| TheNewLab:
modern vacuum cleaners can use up to 12 amps. kitchen appliances also use a lot of current. a hair blow dryer use 1200 watts to 1600 watts. power tools? 7 amp draw on a circular saw..just combine enough on a multiplug outlet, and it will be easy to get up to even 15 watts. If you want to try out a 20 amp circuit. Dedicated circuits for refrigerators and garbage disposals are often 20Amp... Check the mains circuit breaker box for higher amp circuits to test. Still a good idea to start with a variac...make sure unit is OK in the first place. |
| TheNewLab:
ay, yes, microwave ovens are great! |
| Brumby:
A lot of those alternatives can give a qualitative result - with very limited quantitative value. What if the OP wants something to help with calibration? |
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