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Besides checking the voltage and frequency from your multimeter, how could you determine if the generator output is clean. I haven't used an o-scope since trade school, and wouldn't know what to look for, but I do have access to a decent one. It's a 1750 kw genset powered by a cat and just recently when testing it the ats was slow to sync.

First time poster, but long time follower.

Any thoughts?
 

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Besides checking the voltage and frequency from your multimeter, how could you determine if the generator output is clean. I haven't used an o-scope since trade school, and wouldn't know what to look for, but I do have access to a decent one. It's a 1750 kw genset powered by a cat and just recently when testing it the ats was slow to sync.

First time poster, but long time follower.

Any thoughts?
When using a scope test under load. I compared to the building power. Just make sure to have the scope plugged into the generator power because the neutral or grounds are tied together in the scope
 

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Discussion Starter · #3 ·
dronai said:
When using a scope test under load. I compared to the building power. Just make sure to have the scope plugged into the generator power because the neutral or grounds are tied together in the scope
Good point. Would you just look for some ripple or deviation in the frequency? I assume looking at it line to line rather than line to neutral as the ats is a 3 pole and the neutral is tied to the utility. Or would it be better to test line to neutral?
 

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I was getting a false reading for HZ on a hand held meter. So I used the scope to check. Generator company told me to test under load.
 

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Good point. Would you just look for some ripple or deviation in the frequency? I assume looking at it line to line rather than line to neutral as the ats is a 3 pole and the neutral is tied to the utility. Or would it be better to test line to neutral?
Unless you isolate the AC scope power, testing line to line will create a short because the ground clip on the probe is tied to ground. You could test line to neutral or line to line with 2 probes and not connect the ground clips though. It's a bit dangerous unless you are sure of what you are doing.

That being said, it is difficult to accurately measure 60hz with a scope and I wouldn't even bother using a scope on that generator. You could look at the waveform but it's probably not going to tell you why the ATS was slow switching over.
 

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We perform full load test utilizing a Fluke 1750, or an RPM, with resistive load banks to step load the system.
 

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Some ET members told me to test under load but I didn't listen to them.
fify :rolleyes:


Sorry, I will give you credit also :laughing: But I did talk to a tech from the Generator company who confirmed what you said.
 

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Dronai, was this an idling generator or a inverter type generator?
Standby idling type. I also checked with my portable Honda at home, and the same result. With my hand held the reading was at 180 HZ, and 60HZ in the wall outlet ?

The scope shows a dashed sine wave but the measurements look the same. I didn't test under load, but next time I will, as it's supposed to clean up what I'm seeing.
 
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