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Clamp-on Ammeter with Inrush capture.

Hedges said:
I bought that one a few months ago, primarily for 0.01ADC resolution. Still seems to work fine.
Its inrush doesn't capture brief capacitor inrush or transformer inrush.
My 100A current transformer rolls of response for fast (millisecond) inrush peaks.
Both should be OK for "inrush" of motors, some number of 60 Hz cycles.
Click to expand...
Yeah, I have to admit when I bought the HF meter I was really interested in the inductive motor inrush of our well pump, and it worked fine with that. I know I've used it a couple more times successfully, but I'll admit I don't think I tried to check the inrush of an inverter with it.
 
Right, apparently, the HF meter only contained two (2) inrush measurements, I suppose the others leaked out.
The Fluke 381 is now my general purpose DMM, the old Fluke 177 is now a back-up, probably will give it to my son.
 
I have the Fluke 325. It has min/max DC amps, but it isn't clear to me if it does inrush. How different is that than the max? When I looked the selection of Fluke meters I didn't get a good feel for which ones could do inrush. Being new to this I may not have been looking at the right data.
 
Inrush provides hold of high reading, probably one or more line cycles.
Most meters just read what they see at the moment. Maybe some hold what's there when you push a button.
Inrush with a clamp meter should be good for motor starting, which is a few cycles.

What the inrush function of a DMM doesn't seem to capture is inrush charging capacitors, or a transformer which may saturate during the first cycle and draw a large spike. I'm using a current probe with multi kHz bandwidth and digital scope for that.

Your "max" function might do the faster transients I'm looking for:


Another puzzle for me is the "time" aspect of fast trip. I have 5x ... 10x rated current for trip of "C" curve breakers, which I'm sure they'd do if sustained for 10's of milliseconds. But not clear how they respond to brief pulses under 8 milliseconds. There is a solenoid trying to fling a mass, and what higher but shorter duration inrush it will reject isn't clear.
 
Dunno... but when I was checking the starter (inrush) current on my Onan 2500LP generator, people here were quibbling over whether a clamp-on ammeter was the right tool for the job. And I wasn't using some cheapo gadget; I had my (admittedly dated by now) Fluke 33 that I used to use for various motor control work, back when that was my day job.
 
I asked Fluke for a product suggestion for measuring AC inrush, received responses that were not helpful.

Googled "fluke inrush measurement"

www.fluke.com

How to Measure Inrush Current

Knowing the value of inrush current helps technicians locate startup problems
www.fluke.com www.fluke.com

Bought a 381, works great!
 
364A inrush ?
What was he measuring? AC line into a VFD? That would be capacitor bank for a several kW motor.

I was looking into inrush of SMPS, a few 250 W supplies on 208V. I captured about 30A, which was half spec'd max inrush per data sheet for the several supplies in parallel.

I also got 70A for a transformer that would carry 6A at full load.
 
Hedges said:
364A inrush ?
What was he measuring? AC line into a VFD? That would be capacitor bank for a several kW motor.

I was looking into inrush of SMPS, a few 250 W supplies on 208V. I captured about 30A, which was half spec'd max inrush per data sheet for the several supplies in parallel.

I also got 70A for a transformer that would carry 6A at full load.
Click to expand...

I think in his test it was wired 50 times (previously shows the label on the top) ... so really only 7,3A inrush :) .
 
pvdude said:
I asked Fluke for a product suggestion for measuring AC inrush, received responses that were not helpful.

Googled "fluke inrush measurement"

www.fluke.com

How to Measure Inrush Current

Knowing the value of inrush current helps technicians locate startup problems
www.fluke.com www.fluke.com

Bought a 381, works great!
Click to expand...

That's an expensive tool. Not that my 325 was inexpensive, but the 281 would be almost twice a much.
 
I will get much more use out of the $$$ spent on the Fluke, than I spent on this stupid
thing, which is required to program a multiple inverter installation:

Schneider Conext Configuration Tool

The Conext Configuration Tool is used by solar installers to help assist in setup of of their XW system and save on installation time.
www.altestore.com www.altestore.com
 
Last time I did this, I only had a 100A CT to measure current:

diysolarforum.com

Power Factor and Startup Amps

Because I have suitable equipment I'm going to put up measurements I've taken, might help someone with planning a system or general education. Motors draw a startup surge of considerably more amps than they draw while running. With grid power you may see the lights dim briefly, but if you have...
diysolarforum.com diysolarforum.com

Now that I've got a Harbor Freight clamp meter with Inrush and a Fluke i2000, I tried again.

HF Compressor Inrush 050822 1223.jpg compressor 59A inrush IMG_2278.jpg

Clamp meter registered 59A.
"RMS" on scope isn't valid because includes times of low or no amplitude.
"Volts" means "Amps", and scaling factor has been applied.
C3 is 10 turns in CT, 151Vpp / 2 / sqrt(2) = 53Arms inrush (if we pretend waveform is a sine wave)
C4 is Fluke i2000 using 200A scale, 175Vpp / 2 / sqrt(2) = 62Arms inrush

I have a 9kVA toroid transformer. It has 240V, 120V, 120V windings (plus a few extra taps.)
I've used one as autotransformer to get 240V from 120V inverter. Another to make 3x current for testing breakers.

With single 120V winding powered through a switch, I turned it on and off several times. Largest inrush I caught was 22A


Toroid IMG_2284.jpg toroid 21A inrush IMG_2282.jpg Toroid 9kVA Inrush 050822 1347.jpg

I also tried 240V feeding two 120V winding in series, never saw anything higher.
Since 9kVA at 240V is about 40A, I was expecting inrush in the 400A to possibly 1200A range.
Could be this core is sufficiently large to not get very far into saturation with two, 1/120 second half cycles of same polarity.

Later I'll try Variac, up to 240V into a 120V winding to produce B-H curves, maybe also DC. It was DC that let me capture current surge at saturation for a 120VA transformer.
 
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I bought a Kaiweet HT208D. €80 from Amazon.
Yes, it works. It measures DC current. It does inrush. Nice little colour display too.
I measured inrush current on my circular saw. 20A@240V. After the inrush, it draws 4A.

Now, it's interesting, because 240X20 is 4800 (W). My CCC (Cheap Chinese Clone) inverter is 3kW.
It says it can do 6kW for <1s, and, well, it does. I've been using that saw off the inverter quite a a bit lately, I never saw it complain.

Anyway, so far (I've only had it for less than a day) I'm quite pleased with it.
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It delivered peak amps, how about voltage? Can you measure whether that held up for sagged?
A light bulb could give at least a qualitative indication by dimming.

Does the saw start just as eagerly as from utility line, or slower?
Inrush measurement might be just first cycle or part cycle. If a high frequency inverter boosts battery voltage to 340V in a capacitor, that could briefly deliver significant current but capacitor can't store much. Would need boost circuit to keep it full for several cycles starting motor.
For instance, I got 70A peak out of a 6.6A bench supply when testing transformer response to DC step function.
 
It does sag, but... not much, I would say.

Screenshot_0510_155707.png

The saw seems to behave exactly the same as from the generator (I have no grid).
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So both of those are DC measurements, not AC.
Stiff battery hardly dips in voltage. Inverter output voltage may drop (e.g. my house lights dim when a motor starts, likely more from wire resistance than from my 24kW of inverters.)

Your polarity reversal of DC current indicates to me charge current, spike negative is drawn by inverter, charge controller delivers 8A to compensate then tapers back near zero.

But you also got a 20Arms AC inrush measurement?
 
I just measured DC inrush. 98A (!)

dca.png

I'm not sure why it says AC on the display though. The clamp was on the + battery cable.

The AC side... I'll put the 'scope on it when I have a quiet moment. It could be interesting.
Anyway, as per topic, this €80 (~$84.30) DC clamp meter with inrush capture seems to be performing quite well, so far.

[EDIT] Yes, the batteries were fully charged, the controller did just that :·)
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Don B. Cilly said:
I just measured DC inrush. 98A (!)

View attachment 94161

I'm not sure why it says AC on the display though. The clamp was on the + battery cable.

The AC side... I'll put the 'scope on it when I have a quiet moment. It could be interesting.
Anyway, as per topic, this €80 (~$84.30) DC clamp meter with inrush capture seems to be performing quite well, so far.

[EDIT] Yes, the batteries were fully charged, the controller did just that :·)
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Click to expand...

I also made some DC inrush measurements. But I am not sure how accurate they are.
So I would love to see first a comparison or test about it :)
 
I just measured the + battery cable with fridge, computer monitor and a few small loads. PV disconnected.
4.6A. The Victron shunt · on the - cable :·) read 4.3. Not too bad I would say.

Inrush... send me a $800 Fluke and I'll give you a comparison ;·)
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My business has bought a number of meters the is the claim to do in rush but none of meters do it well they perform like crap. We have a Mastech that claims to do it but does not. We have a Uni-T that claims it but it does not work. The only DC meters we have that work for in-rush are fluke.
 
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