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Discussion Starter · #1 ·
Hi guys. I'm having a hard time trying to figure out what's going on with an inverter I just bought. It's a Wen GN400i. Very nice unit. Got it oiled and fueled on Saturday and tested it out. Started right up. Checked AC voltage with a true RMS multimeter which clocked in at 124.5 volts stable. So far, so good.

I checked to see the Hz output. I was expecting a clean and stable 60 Hz signal. Well, that's not what I got. The DMM started jumping from 1 KHz all the way up to 9 KHz and back again. That could not be correct, obviously. Thinking that the DMM might be malfunctioning, I tested the nearby wall outlet. It showed 60 Hz. I fired up my non-inverter genset and it showed a steady 59.7 Hz. So I knew the DMM was working fine.

I added a small load to the inverter to see if that would settle the Hz down so I could get a reading. Nope, no luck. I tried all of the outlets on the inverter, same reading. I tried different holes in the outlets, no difference.

I've seen DMMs have trouble reading Hz on gas generators before. Using a non-TRMS DMM on a non-inverter makes the meter go nuts when set to Hz. However, a True RMS meter is not supposed to be affected by that. I know, typically, high harmonic distortion is what makes reading frequency on non-inverter gensets difficult. The inverter should not have a lot of that, though. The point of inverters is that the power is supposed to be clean.

I decided to connect a Shop Vac to see if that might change things. Same wild Hz readings. Eco mode on or off had no effect, either. I suspect the inverter is outputting at or around 60 Hz. I'm not sure what's causing the instrumentation errors other than very intense line noise, which is concerning for an inverter.

I'm really stumped here. I don't know if I have a bad inverter board or bad cap on the board or if something is not connected that should be, or if all inverters tend to confuse TRMS meters (although I don't think so), or what is going on here. Anyone have any ideas they can share? Thanks!
 

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What meter are you using? I have some "so called" good true RMS meters that do not like inverter power. They read voltage correctly but not Hz. I can plug one "so called" good meter in one socket, and a good Fluke meter in another socket. The Fluke will read 60 Hz, and the other meter will be all over the place. Voltage will read correctly on both meters.
 

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Discussion Starter · #3 ·
What meter are you using? I have some "so called" good true RMS meters that do not like inverter power. They read voltage correctly but not Hz. I can plug one "so called" good meter in one socket, and a good Fluke meter in another socket. The Fluke will read 60 Hz, and the other meter will be all over the place. Voltage will read correctly on both meters.
I have two meters at the house, the TRMS one is an AstroAI which is supposed to be a Fluke clone and I have a non-RMS DMM from Harbor Freight. Neither seems able to return an accurate Hz reading. I wasn't sure if there was something inherent about inverter power which confuses all but the best meters or if there is something about my inverter in particular which is making the meters crazy. I has assumed that because the signal is supposed to be much cleaner that at least the TRMS meter would have no trouble getting a Hz read. I have a couple of non-inverter gensets, but this is my first inverter. The TRMS has difficulty with my Firman generator but reads my Coleman Powermate with no issues. The Firman THD can get as high as 25% from what I understand, so I presume that's why Hz can be a bear to read even with a TRMS meter.
 

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I don't think you need to worry about the Hz output with your inverter generator. As long as the voltage is good, the Hz should be ok. I'm sure the issue is with your multimeter.
The multimeter I have that gives me bad Hz readings is a Radio Shack 46-Range Digital Multimeter with PC Interface which is a pretty good meter. I have two Fluke meters and they both read a steady 60 Hz.
 

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One simple test for proper Hz: plug an old-fashioned electric clock into the genset and compare the seconds hand with a stopwatch: 60 seconds = 60 Hertz. 59 = 59. 61 = 61. Etc.
 

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stick with a fluke meter...
cheap low cost meters will just make more work for you!.
the killawatt meters are ok for small generator work...
just to get you in the ball park.

but if you are to be serious about doing electrical and electronics work use a good fluke!
 

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Discussion Starter · #7 ·
I don't really use DMMs very much, not really enough to get something high end like a Fluke. Although I'd love to have one!

I suspect the Wen is generating at or around 60 Hz. I was just puzzled about the noise on the line when trying to measure it, given that inverters are supposed to be clean power. If the THD is in the 3-4KHz range, is that still considered clean power? In other words, let's say that the DC to AC conversion is not filtered well and that's what I'm picking up with the DMM... I'm thinking noise in that range is not a problem for electronics? Therefore, even though it's present, it's still considered clean power by genset standards. Does that make sense?

In other words, the listed 3% THD is only in the bad range, where it actually matters. If so, that makes a lot more sense to me. I'm totally new to inverters, so I have no idea what kind of signal it puts out and how it's different from regular gensets. If the power was dirty in the 60 Hz range, that would be a lot more trouble for electronics, if my logic is correct.
 

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i think fluke meters start at 130.00...
the better ones run at 250-300...
fluke is an investment.
and yes they hold value!
 

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Discussion Starter · #9 ·
i think fluke meters start at 130.00...
the better ones run at 250-300...
fluke is an investment.
and yes they hold value!
I was looking at Fluke meters about a year ago. I was trying to figure out the frequency output on a Coleman Powermate that my brother in law gave me. The generator was from around 2004 or so. He used it during the aftermath of Hurricane Gustav and then stuck it in his garage. It sat there for about 12 years. He had gotten a whole house generator, so he didn't need the Coleman anymore. It took quite a bit of TLC, but I got it back up and running again. I had read that the generator part was made by Generac, back before they sold the company. The Fluke clone I got reads the frequency perfectly, so I didn't see the need for anything beyond that until now.

I'm sure a Fluke DMM would tell me my Wen is putting out 60 Hz. I'm just curious if I have a lot of line noise since my current DMM is reading wildly. Maybe I just need to break the inverter in. Since this is my first inverter, I'm not sure if the situation will improve. I really just need something that's not going to bake my electronics in the next power outage if I need to use inverter power.
 

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yea you might want to get your hands on a spectrum analyzer to see the full spectrum...
if you have any friends with hard core labs near by they might help you on this.

my last spectrum unit was $60K ... lol no lone out to others or letting them use it on that tool!!
there are places that lease them.
but if you are doing a big project.
check for them used on ebay...
and have them re certified.
 

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I was looking at Fluke meters about a year ago. I was trying to figure out the frequency output on a Coleman Powermate that my brother in law gave me. The generator was from around 2004 or so. He used it during the aftermath of Hurricane Gustav and then stuck it in his garage. It sat there for about 12 years. He had gotten a whole house generator, so he didn't need the Coleman anymore. It took quite a bit of TLC, but I got it back up and running again. I had read that the generator part was made by Generac, back before they sold the company. The Fluke clone I got reads the frequency perfectly, so I didn't see the need for anything beyond that until now.

I'm sure a Fluke DMM would tell me my Wen is putting out 60 Hz. I'm just curious if I have a lot of line noise since my current DMM is reading wildly. Maybe I just need to break the inverter in. Since this is my first inverter, I'm not sure if the situation will improve. I really just need something that's not going to bake my electronics in the next power outage if I need to use inverter power.
I'm sure your generator is just fine. Like I said before my Fluke reads the Hz on my inverter right at 60Hz. My RadioShack digital multi meter gives Hz readings all over the place.
I wouldn't worry about the readings you were getting.
 

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Discussion Starter · #12 ·
I'm sure your generator is just fine. Like I said before my Fluke reads the Hz on my inverter right at 60Hz. My RadioShack digital multi meter gives Hz readings all over the place.
I wouldn't worry about the readings you were getting.
I think you're right. I would be none the wiser had I not put a multimeter to it. It runs fine and power output is right on the money. I'm pleased to finally have an inverter rather than having to think of ways to smooth out the power from my other non-inverter gensets. My plan is to run the power through a Furman line conditioner before connecting the TV, router, DVD player, and other electronics. I'm hoping that will reduce any noise that's on the line.

I want to use the non-inverter gensets for the window a/c units and fridges. The window shakers have electronic thermostats and controls, as do the fridges. Can I safely use them with the non-inverter generators? Specifically, I have a Coleman Powermate 6250 from around 2004 or so. I don't know if it has AVR from that vintage. I know my Firman does, but it's rated at up to 25% THD. That's a bit on the high side. No idea what the THD for the Coleman is, but it's probably not low. How safe would they be to use in those applications?
 

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I think you're right. I would be none the wiser had I not put a multimeter to it. It runs fine and power output is right on the money. I'm pleased to finally have an inverter rather than having to think of ways to smooth out the power from my other non-inverter gensets. My plan is to run the power through a Furman line conditioner before connecting the TV, router, DVD player, and other electronics. I'm hoping that will reduce any noise that's on the line.

I want to use the non-inverter gensets for the window a/c units and fridges. The window shakers have electronic thermostats and controls, as do the fridges. Can I safely use them with the non-inverter generators? Specifically, I have a Coleman Powermate 6250 from around 2004 or so. I don't know if it has AVR from that vintage. I know my Firman does, but it's rated at up to 25% THD. That's a bit on the high side. No idea what the THD for the Coleman is, but it's probably not low. How safe would they be to use in those applications?
I don't think you need to worry about your other appliances with the other generators.
People have been running their homes on standard generators for years. Most people don't even have a concept about THD and dirty power. The main thing is to monitor the voltage output.
I just posted the results of the output of my big Generac. The THD changes with different loads ant kind of loads.
Just the basics posted here:
 

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Discussion Starter · #14 ·
I don't think you need to worry about your other appliances with the other generators.
People have been running their homes on standard generators for years. Most people don't even have a concept about THD and dirty power. The main thing is to monitor the voltage output.
I just posted the results of the output of my big Generac. The THD changes with different loads ant kind of loads.
Just the basics posted here:
The voltage output in the Coleman is 122 volts and 59.7 Hz with no load. I'm wondering if I need to bump that up a bit, maybe to around 125 VAC with no load.

I haven't checked the Firman in a while, so I don't recall the output on it. I haven't adjusted the idle on it, so I presume it's still good to go.
 

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Discussion Starter · #15 ·
An interesting update to the story that I think you guys will like.

This morning, I finally got a chance to play around with the inverter. I replaced the Torch spark plug with an NGK plug. I tested voltage and Hz again. Same results, voltage stable at 124.5 and Hz all over the place. I pulled out my line conditioners to see what effect they might have.

I tried the Furman first. I was able to get 59.99 Hz, but it would still bounce around a bit. Not nearly as badly as without it, but it wasn't very stable. But, the good news is that I was able to finally get an accurate reading, momentarily, at the correct Hz. So, the Furman power conditioner certainly was a big help in the right direction.

The big news was with my Tripp Lite Isobar conditioner. That seems to be the silver bullet. Solid 59.99 Hz reading, stable. Voltage read properly. Needless to say, I was very happy to see that. That was the first time I've tested the Isobar like that and I was impressed. I have a smaller one that I use with some florescent light fixtures in my kitchen that were causing a lot of noise on the circuit and it works very well for that. I had my fingers crossed that I might see a solution by using one with the inverter.

I also tested one of the nicer surge protectors I have just to see if it might provide some benefit, but it didn't really do much to help with the Hz readings. I am stoked, to say the least.

Thoughts, guys?
 

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An interesting update to the story that I think you guys will like.

This morning, I finally got a chance to play around with the inverter. I replaced the Torch spark plug with an NGK plug. I tested voltage and Hz again. Same results, voltage stable at 124.5 and Hz all over the place. I pulled out my line conditioners to see what effect they might have.

I tried the Furman first. I was able to get 59.99 Hz, but it would still bounce around a bit. Not nearly as badly as without it, but it wasn't very stable. But, the good news is that I was able to finally get an accurate reading, momentarily, at the correct Hz. So, the Furman power conditioner certainly was a big help in the right direction.

The big news was with my Tripp Lite Isobar conditioner. That seems to be the silver bullet. Solid 59.99 Hz reading, stable. Voltage read properly. Needless to say, I was very happy to see that. That was the first time I've tested the Isobar like that and I was impressed. I have a smaller one that I use with some florescent light fixtures in my kitchen that were causing a lot of noise on the circuit and it works very well for that. I had my fingers crossed that I might see a solution by using one with the inverter.

I also tested one of the nicer surge protectors I have just to see if it might provide some benefit, but it didn't really do much to help with the Hz readings. I am stoked, to say the least.

Thoughts, guys?
I have to say that you're good to go. I do suggest that you invest in a quality multi meter though.
 

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Discussion Starter · #17 ·
I think I will also use the Isobars with the regular gensets as well. They seem to quiet down a lot of the line noise. They won't cure a stepped sine wave, but it should be fine for the fridge and freezer until the lights come back on.
 

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Discussion Starter · #19 ·
we use isobars on all of the BIG screen tv projectors.
works great on the 24 foot projector.
I really like the Isobar power strips. They seem pretty heavy duty and do a good job of cleanup.

My only concern now is that my inverter might be defective since my DMM was picking up a lot of noise. Of course, a high end Fluke DMM might not have picked up any of it at all and just shown 60 Hz straight from the outlet. It seems if I had a defective unit, I'd be seeing voltage flux as well, but I don't really know. Has anything I've described led any of you guys to believe I might have a defective inverter?
 

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a good wide band spectrum unit will show all of the inverter trash...

it could be an internal filter bad!
they use an LC ckt in the inverters to hold down the trash...

I am working on a set of school videos for 2021 / 2022 honda school that shows the trash for engineering class.
subtle differences in the inverter internals specs will show up as hash or signal trash...

all that stuff like time shift etc play in to the fq deviation.
and then power factor as well...

if you small electronics has real good power supplies and good filtering on the ac to dc converters
you will not notice the bad power...
but over time the filters will fail if they are feed a steady diet of super trash!
 
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