What tester to use to measure in-rush current?
- Thread starter rottalpha
- Start date
Something along these lines.
http://en-us.fluke.com/training/tra...rs/how-and-why-to-measure-inrush-current.html
http://en-us.fluke.com/training/tra...rs/how-and-why-to-measure-inrush-current.html
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fernarias
Super Member
You need a data logging MM that measure current over a time interval and then saves it, like a fluke 287. Or if your fluke has the min/max setting: http://www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/dmms/under-used_functions as stated above
triode17
Super Member
Would that be inrush from the AC outlet? I need to measure inrush on a high voltage secondary side to determine the max. current through the SS rectifiers.
Did you use a very slow sweep to capture it on the scope, then expand it?
I have a Fluke 187 I think it is, with the data logging. Used it just the other day to measure the inrush on a 1 KVA 480V to 120V control transformer.
When I arrived it had one of the primary fuses blown, a 7A dual element time delay type. Replaced it with the same type, added my current clamp to one of the primary leads and turned it on. Max current it picked up was about 50mA. Blew out both primary leg fuses!
Disconnected primary leads and ohm input terminals to chassis ground. 0.68 ohms on one side and 1.5 ohms to ground. Dead shorted to ground!
Installed new transformer and fuses today, works fine.
Rechecked the old transformer and now it's showing no shorts. Fully potted unit, looks new. I figure it had a hit from an electrical storm that happened the night before. First time I checked it was right after blowing both fuses, the shorted area was probably still hot. Cooled down it looked fine.
I've always heard that a failed electrical component makes a loud thud if tossed into a dumpster. This one went thud loudly.
BillWojo
When I arrived it had one of the primary fuses blown, a 7A dual element time delay type. Replaced it with the same type, added my current clamp to one of the primary leads and turned it on. Max current it picked up was about 50mA. Blew out both primary leg fuses!
Disconnected primary leads and ohm input terminals to chassis ground. 0.68 ohms on one side and 1.5 ohms to ground. Dead shorted to ground!
Installed new transformer and fuses today, works fine.
Rechecked the old transformer and now it's showing no shorts. Fully potted unit, looks new. I figure it had a hit from an electrical storm that happened the night before. First time I checked it was right after blowing both fuses, the shorted area was probably still hot. Cooled down it looked fine.
I've always heard that a failed electrical component makes a loud thud if tossed into a dumpster. This one went thud loudly.
BillWojo
whoaru99
Epic Member
Yeah, I use fairly slow sweep relative to typical electronics measurement but it doesn't have to be all that slow. The high peaks I've seen come within the first cycle or two; usually the first half to one cycle. Maybe depends if there is any sort of inrush limiting, startup cushioning, etc.
thank you everyone,
This is very helpful. I think I will go for a purposly built Fluke like model 381 clamp meter.
I did not think of that, Thank you!
yes, that would be one of the goals....properly sizing that rectifier
Edit: For a factory amp, for which I replaced main PSU caps with a larger value, I intend to find out what is the unwanted increase in terms of In-rush current. I know it can be calculated, but I am no EE.
Thank you everyone for your input!
This is very helpful. I think I will go for a purposly built Fluke like model 381 clamp meter.
yes, SS Audio amp
I did not think of that, Thank you!
yes, that would be one of the goals....properly sizing that rectifier
Edit: For a factory amp, for which I replaced main PSU caps with a larger value, I intend to find out what is the unwanted increase in terms of In-rush current. I know it can be calculated, but I am no EE.
Thank you everyone for your input!
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