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Your scope may offer some hints as to why the waveforms differ:

First, can you share what the Volts/Division setting is each of the photos

Your scope also likely has the ability to display Vpp (voltage peak to peak) and RMS voltage. It would be interesting to see what these values are!
 

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Your scope may offer some hints as to why the waveforms differ:

First, can you share what the Volts/Division setting is each of the photos

Your scope also likely has the ability to display Vpp (voltage peak to peak) and RMS voltage. It would be interesting to see what these values are!
For which generator?
 

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I guess the one you're most concerned about ................. the Champion??
I have that generator at another location, so I don't have access to it now. But yeah, that waveform was not was I was expecting from an inverter. The only way I got away from that reading was by plugging in the bonding-neutral plug. That tells me that it has something to do with grounding. Maybe the inverter board is not grounded correctly? Has anyone seen something like that before? I would presume that the inverter should be making a very nice sine wave without having to plug anything in to it, right?

I can make it work using the plug, granted, but I'm genuinely curious about why I might have to.
 

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I have a friend who has a Homelite generator, the UT905700. It looks like a pretty nice unit. It's got a Yamaha engine, for what that's worth. My friend picked it up from Home Depot just before Hurricane Isaac in 2012. He used it for about 5 days during the outage after the storm passed. It appears to have been kept outside for at least a couple of years on a back porch. I told him I'd take it back to the workshop and see if I could get it running again. The gas in the carb did not look or smell like gas. It was... nasty. I took the carb apart and soaked the jets and emulsion tube in Seafoam. Drained and cleaned out the gas tank. I replaced the rubber fuel line and filter. The original oil was in it and it looked bad. I changed it with Mobil 1. Using fresh gas, it runs fine now. I told him he's going to keep it in his garage from now on. This is the unit:

9897

I let it run for a while to make sure all was well. While it was running, I captured some waveforms for you guys. I also wanted to make sure it was putting out power.

9898


It's no inverter signal, but it's better than I had expected. It looks better than my Firman.

9899


I wouldn't power anything too sensitive with it, but my guess is that it would be fine for fridge and window a/c work.

9900


The engine is a Yamaha model. I don't know who makes the other components. Seems like a nice generator.
 

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Discussion Starter · #106 ·
I have a friend who has a Homelite generator, the UT905700. It looks like a pretty nice unit. It's got a Yamaha engine, for what that's worth. My friend picked it up from Home Depot just before Hurricane Isaac in 2012. He used it for about 5 days during the outage after the storm passed. It appears to have been kept outside for at least a couple of years on a back porch. I told him I'd take it back to the workshop and see if I could get it running again. The gas in the carb did not look or smell like gas. It was... nasty. I took the carb apart and soaked the jets and emulsion tube in Seafoam. Drained and cleaned out the gas tank. I replaced the rubber fuel line and filter. The original oil was in it and it looked bad. I changed it with Mobil 1. Using fresh gas, it runs fine now. I told him he's going to keep it in his garage from now on. This is the unit:

View attachment 9897
I let it run for a while to make sure all was well. While it was running, I captured some waveforms for you guys. I also wanted to make sure it was putting out power.

View attachment 9898

It's no inverter signal, but it's better than I had expected. It looks better than my Firman.

View attachment 9899

I wouldn't power anything too sensitive with it, but my guess is that it would be fine for fridge and window a/c work.

View attachment 9900

The engine is a Yamaha model. I don't know who makes the other components. Seems like a nice generator.
The engine is certainly its best attribute. Every time you post waveform I get closer to upgrading to a real mans scope lol.
 

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lol dr!
yea the fluke power meter might be the ticket!

kinda crazy on the bumps on the different gens...
must be the rotor slot noise...
we had trash like that on the BIG 1200 hp electric motors....
on motor spin down braking it was bad enough to trip out the inverter drive for the motor.

it was a flashed over slot bars on the rotor...
pretty cool!
yea the expensive spectrum unit found that one!
$250k later in motor and drive repairs it was back up and running!
 

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Drmerdp, I wanted to mention to you that if you're in the market for a scope, keep an eye on the Rigol clearance site. They don't have much at the moment, but they just did a huge sale not long ago. Some of the scopes were going for 75% off. I almost picked up another one but resisted the urge. They go pretty fast, so you'll need to watch the page. If you catch the sale right, you can pick up something really nice for a huge discount.

Clearance | RIGOL
 

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Picked up another waveform from a generator, this time a Firman T07571. It's a tri-fuel non-inverter generator. A friend of mine picked it up right before Ida. It worked fine except the electric start stopped working on it almost immediately. I told him I'd stop by today and take a look at at. We got Firman tech support on the line to try to diagnose what might be wrong. Tech support ended up concluding the solenoid was bad and is sending my friend a new one and a new switch. I'm hopeful that solves the issue. The unit can still be started with the pull cord, but he wants to be able to use the electric start, naturally.

I took the opportunity to attach the scope. The results are surprisingly good from what I can tell.

This is the unit:

Tool Toy Wheel Gas Automotive tire


These are the waveforms:
Slope Rectangle Font Line Parallel


A bit of sag but not too bad looking for a non-inverter.

Light Rectangle Slope Font Plot







Rectangle Slope Organism Font Line


I'm not sure why the voltage is showing around 60 VAC. That doesn't make much sense. Hz looks correct. I tested voltage with a DMM and it showed around 124 VAC. I've never had my scope be that off before with the voltage reading. I can't seem to get an accurate reading on voltage for some reason.

Seems like a nice generator. The tri-fuel option is nice, especially considering how difficult it was to get gasoline after the storm.
 

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Discussion Starter · #111 ·
Looks typical for the price point. The top of the wave is better then the bottom. It’s a good buy all things considered.

Thanks for posting more waveforms pics.
 

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“I'm not sure why the voltage is showing around 60 VAC. That doesn't make much sense. Hz looks correct. I tested voltage with a DMM and it showed around 124 VAC.”

I’m guessing it’s because of where your measurement cursors are positioned…..?
 

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“I'm not sure why the voltage is showing around 60 VAC. That doesn't make much sense. Hz looks correct. I tested voltage with a DMM and it showed around 124 VAC.”

I’m guessing it’s because of where your measurement cursors are positioned…..?
To be honest, I'm not sure. As far as I know, I don't have the cursors set. I really just wanted to get a VAC reading from the output. Testing other generators, I've gotten close to 120 VAC from the probe. I haven't changed any settings. When I need an accurate VAC reading, I just use my DMM. I'll have to keep doing that until I can figure out what's causing the weird readings on the scope.
 

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a bit lumpy but that can be slot distortion in the rotor or stator.
did you get a reading with a bit of a load?
and incandescent light would be a good load .... something with out a motor in it.

that brings up a great idea why they do not use square or rectangle wire or potted wire in the gens...

think on this
if the wires were perfectly tuned in the slots you should have a perfect wave...
 

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To be honest, I'm not sure. As far as I know, I don't have the cursors set. I really just wanted to get a VAC reading from the output. Testing other generators, I've gotten close to 120 VAC from the probe. I haven't changed any settings. When I need an accurate VAC reading, I just use my DMM. I'll have to keep doing that until I can figure out what's causing the weird readings on the scope.
Post #112 is your clue. Move your your measurement cursors to the top and bottom of the waveforms and watch the voltage readout change.
 

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To be honest, I'm not sure. As far as I know, I don't have the cursors set. I really just wanted to get a VAC reading from the output. Testing other generators, I've gotten close to 120 VAC from the probe. I haven't changed any settings. When I need an accurate VAC reading, I just use my DMM. I'll have to keep doing that until I can figure out what's causing the weird readings on the scope.
1) Is this waveform taken from a floating neutral generator?

2) If so, and based on your probe connections, this may be nothing more than Ghost Voltage you are measuring ........................ which is very likely since you are reading around 60 VAC.
 

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PowerMate PM0126000 No Load



PowerMate PM0126000 Half Load
That ds212 looks like a convenient little piece of equipment. After reading through many of the posts and looking at other posts on how to calculate THD apparently most scopes require a Fourier transform calculation to get to a percentage answer. Most lower analyzer meters will make the calculation. I haven’t done a Fourier transform since college and being honest probably couldn’t even do one now. Does this ds212 perform the calculation or does it require the math to be done manually?
if it’s calculated for me…a hundred off Amazon is well worth it for me to see how my generator is performing.
cheers.
 

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That ds212 looks like a convenient little piece of equipment. After reading through many of the posts and looking at other posts on how to calculate THD apparently most scopes require a Fourier transform calculation to get to a percentage answer. Most lower analyzer meters will make the calculation. I haven’t done a Fourier transform since college and being honest probably couldn’t even do one now. Does this ds212 perform the calculation or does it require the math to be done manually?
if it’s calculated for me…a hundred off Amazon is well worth it for me to see how my generator is performing.
cheers.
This is what I use for THD readings.
Fluke 345 Power Quality Clamp Meter
I have a regular scope as well, but it does not give THD readings. Equipment for those readings is rather expensive.
 

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After replacing the Torch plug and putting in oil and fuel, I was able to capture some waveforms from my new Wen 56225i inverter. First, the inverter:

Plant Gadget Camera accessory Personal protective equipment Cameras & optics

Once you remove the side panel, everything seems fairly easy to get to. It started up without incident and ran very smoothly. I got my DMM out and the inverter tested at 124.5 VAC, identical to my GN400i. Just like with the 400i, I could not lock onto a Hz reading. It jumped all over the place. It's probably a DMM issue. Next was the scope.

Power output was not very smooth at first. It was jumpy and a bit jagged:


Slope Rectangle Font Line Handwriting


Black Slope Rectangle Font Plot


I discovered that this Wen has the same issue as the Champion. You have to use the neutral bonding plug. For some reason, that cleans up the signal on the scope. Notice the Hz reading. That will become relevant later.

I was still getting weird readings, even after using the neutral bonding plug. The display was a bit erratic and jumped around. Plus, the Hz readings kept jumping up and down. That was strange. I hadn't seen that before when testing my other generators, even the non-inverter ones. There was some noise in the signal as well, which was also out of place.

Light Black Slope Plot Font


I caught it on one of the frequent Hz bursts to above 80 Hz.

Rectangle Slope Font Line Parallel


I was a bit perplexed. The other inverters I have don't do that. Hz is always stable, as is VAC. I started brainstorming to try to figure out what was going on. Why was I getting such anomalous readings from this inverter?

I had to run a fairly long power cable from the scope to the wall outlet in the garage. I noticed that the power strip I was using that was connected to wall power looked old. It was yellowed and very worn looking. I wondered if I might be having issues because of that. I removed the old power strip and replaced it with a known-good APC one. After that, the signal seemed to clear up considerably.

Light Black Slope Line Rectangle


The Hz stopped jumping up and down as well. It remained stable at 60 Hz, as you would expect.

Slope Font Plot Line Parallel


Apparently, from what I saw, the old power strip I was using to power the scope was causing strange readings from the inverter. I'm not sure how that would happen, but once I removed the old strip from the power chain, the readings cleared up and the inverter readings became what you'd see from any other inverter. VAC is off, but that appears to be because my cursors are not set correctly. I did confirm the inverter is outputting 124.5 VAC, though.

I pulled the old power strip out of my rotation since it seems to be causing issues. My takeaway is to make sure the scope is getting clean power from the wall or readings might be wonky.
 

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I had to run a fairly long power cable from the scope to the wall outlet in the garage.
If you're willing, you might won't to conduct one other test to see if it makes any difference in your results. Instead of plugging your scope into one of you home's wall outlets, plug the scope into one of the generator's outlets and then conduct the same test. Of course, if the wall outlet is receiving its power from the generator, then forget what I am suggesting ........ as it won't make any difference at all.

If the wall outlet you utilized truly isn't receiving its power from the generator, then I'd be curious to see if the home's ground conductor was possibly the source of your anomaly .................. anyway, just a thought!
 
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