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Old 11-05-2021, 12:52 PM   #1
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Portable Generator v. Portable Generator-Inverter

11-5-2021
Facts (as I know them):
1. All portable generators create direct current (DC)
2. All portable generators create alternating current (AC)
3. To convert DC to AC requires an inverter
4. Therefor all portable generators [that create AC] are portable "generator-inverters"
What's wrong with that logic?
Regards,
M.
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Old 11-05-2021, 01:44 PM   #2
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"Facts (as I know them):
1. All portable generators create direct current (DC)"


For the most part this is true in practice, but not necessary. Many produce 12 volts to charge its starting battery.

"2. All portable generators create alternating current (AC)"

Again, for the most part this is true in practices, but not necessary. Generators can be designed to produce either AC or DC power.

"3. To convert DC to AC requires an inverter"

This is usually true.

"4. Therefor all portable generators [that create AC] are portable "generator-inverters"
What's wrong with that logic?"


Traditionally portable AC generators were controlled by fan and carburetor butterfly valve with a wind paddle. Voltage and frequency were adjusted mechanically. They produced relatively clean AC power but required periodic re-calibration. The engine must be run at a precise RPM for precise AC output.

Late model inverter generators use an inverter to create clean precise output. The inverter frequency and voltage can be precisely controlled using electronic circuits. The AC output can be automatically synchronized with another AC generator.

Engine speed does not need to be kept constant to maintain voltage and frequency. Engine speed can be decreased to reduce noise and fuel consumption. The inverter maintains the precise voltage and frequency. It increases engine speed when more power is required.
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Old 11-05-2021, 01:56 PM   #3
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Portable generators produce 120 or 120/240 volt AC current.
Depending on how many magnetic polls in it, they need to run at 3600, 1800 or 900 RPMs for 60 hz.

Portable inverter generators produce AC that is converted to DC and ran thru an inverter. The inverter inverts it to 120 volt hours.

That's why they can be variable speed, depending on load.
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Old 11-05-2021, 02:06 PM   #4
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Quote:
Originally Posted by Aharmmms View Post
11-5-2021
Facts (as I know them):
1. All portable generators create direct current (DC)
2. All portable generators create alternating current (AC)
3. To convert DC to AC requires an inverter
4. Therefor all portable generators [that create AC] are portable "generator-inverters"
What's wrong with that logic?
Regards,
M.
To understand your logic completely you need to be an electrical engineer. But my understanding of generators is they create ac current by spinning a magnet in a loop of wire. As it rotates 180 degrees it reverses the direction of the current flow. So yes, it is producing DC current that reverses direction 120 times a second, creating 60hz AC current. So in reality, your logic is wrong.

In a generator they tap current in two places and ground. That’s what produces AC current. There is no inversion involved. It requires a constant speed to produce a consistent frequency. So on a portable generator the speed must be held steady, despite the load.

An inverter can do this electronically. Electronics on a portable generator can also do this by regulating the exact time the current changes direction no mater the speed of the generator.

Nice try though.
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Old 11-05-2021, 03:02 PM   #5
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Quote:
Originally Posted by Persistent View Post
....
Traditionally portable AC generators were controlled by fan and carburetor butterfly valve with a wind paddle. Voltage and frequency were adjusted mechanically. They produced relatively clean AC power but required periodic re-calibration. The engine must be run at a precise RPM for precise AC output.

.....
My 800 watt $88 HF generator voltage and frequency can be adjusted can be adjusted with a Phillips screw driver.

Typically when load is added to a generator is slows and voltage drops. This is call droop. Depending on the control system, it may not return to 120 vac and 60 hz.

To compensate for the control system on my cheap construction type, I would set the unloaded at 140 volts 66 HZ. As soon as it was plugged in drop down to 60 HZ and 120 vac.

My 6500 watt Onan has an electronic voltage and frequency controls. So even large loads are restored to close to 60 hz and 120 vac very fast.

Synchronous generators produce pure sine wave alternating current.
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Old 11-05-2021, 03:06 PM   #6
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Originally Posted by twinboat View Post
....

Portable inverter generators produce AC that is converted to DC and ran thru an inverter. The inverter inverts it to 120 volt hours.

.....
Do you happen to know how efficient this process is?
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Old 11-05-2021, 04:21 PM   #7
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Cheap generators produce AC directly with a rotating armature and magnetic fields. This is why maintaining a specific RPM is so important as too high rpm and the frequency is too high... to low rpm and the frequency is too low. Cheap generators (contractor generators) DO NOT have an inverter. The electric power tends to be noisy due to fluctuations in rpm and static from the armature brushes and slip rings. Regardless of load, this type of generator must maintian a constant RPM to output 60hz (US).

Inverter generators start out the same as the above, but take the AC output of the generator armature, converts it to DC, then the inverter changes the DC back to AC. The advantages to doing this include cleaner power and engine RPM can vary with load (which saves fuel and reduces noise) without affecting the quality of the power since the inverter, not the engine RPM, maintains the sine wave and frequency of the AC that is provided to the user.

https://www.electricaleasy.com/2019/...rator.html?m=1

It's a common misconception that a generator only outputs DC power. It depends if the generator is equipped with fixed brushes (like on a battery powered motor) and/or Slip Rings. If the generator uses fixed brushes, it outputs DC, if it uses slip rings, it outputs AC power. A generator can be equipped with both to produce AC and DC at the same time.

https://en.m.wikipedia.org/wiki/Slip_ring
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Old 11-05-2021, 06:06 PM   #8
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Originally Posted by jrollf View Post
Cheap generators produce AC directly with a rotating armature and magnetic fields. This is why maintaining a specific RPM is so important as too high rpm and the frequency is too high... to low rpm and the frequency is too low. Cheap generators (contractor generators) DO NOT have an inverter. The electric power tends to be noisy due to fluctuations in rpm and static from the armature brushes and slip rings. Regardless of load, this type of generator must maintian a constant RPM to output 60hz (US).

Inverter generators start out the same as the above, but take the AC output of the generator armature, converts it to DC, then the inverter changes the DC back to AC. The advantages to doing this include cleaner power and engine RPM can vary with load (which saves fuel and reduces noise) without affecting the quality of the power since the inverter, not the engine RPM, maintains the sine wave and frequency of the AC that is provided to the user.

https://www.electricaleasy.com/2019/...rator.html?m=1

It's a common misconception that a generator only outputs DC power. It depends if the generator is equipped with fixed brushes (like on a battery powered motor) and/or Slip Rings. If the generator uses fixed brushes, it outputs DC, if it uses slip rings, it outputs AC power. A generator can be equipped with both to produce AC and DC at the same time.

https://en.m.wikipedia.org/wiki/Slip_ring
Since I have 3 generators I am skeptical of claimed benefits of inverter generators.

Worked in the power industry for 50 years and never heard the term 'clean' electricity. It is a marketing term.

Both my portable generators are noisy Under heavy load which includes charging batteries. I find the changing speeds of the inverter generator irritating. I do not run my generators very long, 30 - 60 minutes.

When I take a shower when dry camping I like to use propane and electric at the same time. With the hot water of the inverter, it is running flat out. Since the electric cuts off at a lower temperature than propane, I am close to the max temperature for a shower when the inverter generator slows down.
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Old 11-13-2021, 09:41 AM   #9
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Originally Posted by followingsea View Post
Since I have 3 generators I am skeptical of claimed benefits of inverter generators.



Worked in the power industry for 50 years and never heard the term 'clean' electricity. It is a marketing term.



Both my portable generators are noisy Under heavy load which includes charging batteries. I find the changing speeds of the inverter generator irritating. I do not run my generators very long, 30 - 60 minutes.



When I take a shower when dry camping I like to use propane and electric at the same time. With the hot water of the inverter, it is running flat out. Since the electric cuts off at a lower temperature than propane, I am close to the max temperature for a shower when the inverter generator slows down.
Clean is a generic term for low total harmonic distortion (THD). I've experienced the problems of cheap generators with high/bad THD. Used a contractor generator during a week long power outage at home. The lights flickered giving me headaches, the fridge sounded like it was dying (you could hear it in living room), the ceiling fan had an awful whine to it, and my computer UPS refused to use it.

Bought a much nicer inverter generator, all the issues went away and everything works now just like when I have power from the grid.

https://www.allaboutcircuits.com/tec...power-systems/

"Total harmonic distortion (THD) is an important aspect in power systems and it should be kept as low as possible. Lower THD in power systems means higher power factor, lower peak currents, and higher efficiency. Low THD is such an important feature in power systems that international standards such as IEC 61000-3-2 set limits on the harmonic currents of various classes of power equipment."

https://generatorbible.com/blog/what-is-thd/

"IEEE Standard 519-2014 advises on the permissible harmonic distortion limit for electronic equipment. As per the article, computers and allied equipment like programmable controllers typically require AC sources that have no more than a 5% harmonic voltage distortion factor, with the largest single harmonic being no more than 3% of the fundamental voltage.

Harmonics above the permissible limit can cause malfunctioning of the electronic equipment. A higher percentage of harmonic distortion may even burn sensitive components.

The harmonic distortion in conventional generators is generally in the range of 9–10%. For some generators, it can be even higher than that (manufacturers will often say “under 25%”, as it also depends on the load). Due to such high distortion, these generators are not suitable for circuits which contain computers, laptops, TVs and other sensitive electronic equipment. It is worth noting that conventional generators with low THD exist, but are somewhat of an exception.

Contrary to this, a portable inverter generator’s distortion is in the 3–5% range, sometimes even lower. This range is well within the permissible limits of IEEE std 519-2014. Therefore, the electricity generated by portable inverter generators is safe (clean) for computers, laptops, TVs, etc."
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Old 11-13-2021, 10:03 AM   #10
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Quote:
Originally Posted by Aharmmms View Post
11-5-2021
Facts (as I know them):
1. All portable generators create direct current (DC)
2. All portable generators create alternating current (AC)
3. To convert DC to AC requires an inverter
4. Therefor all portable generators [that create AC] are portable "generator-inverters"
What's wrong with that logic?
Regards,
M.
It's based on a logical fallacy.
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Old 11-15-2021, 12:00 AM   #11
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Quote:
Originally Posted by jrollf View Post
Clean is a generic term for low total harmonic distortion (THD). I've experienced the problems of cheap generators with high/bad THD. Used a contractor generator during a week long power outage at home. The lights flickered giving me headaches, the fridge sounded like it was dying (you could hear it in living room), the ceiling fan had an awful whine to it, and my computer UPS refused to use it......
Thank your for the response.

Are you an electrical engineer? Still looking for a good explanation.

"Paul, manger and editor ....." would appear to be more focused on marketing.

What was the voltage and frequency at the loads during your home power outage?

Those parameters would explain your problems not TDH.

Clearly portable generators have limitations.
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Old 11-15-2021, 05:06 AM   #12
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Portable Generator v. Portable Generator-Invertor

Quote:
Originally Posted by Aharmmms View Post
11-5-2021
Facts (as I know them):
1. All portable generators create direct current (DC)
2. All portable generators create alternating current (AC)
3. To convert DC to AC requires an inverter
4. Therefor all portable generators [that create AC] are portable "generator-inverters"
What's wrong with that logic?
Regards,
M.


I think this is based upon the old terminology used in cars many decades ago…… in cars, if they had a “generator” it produced DC current. If it was a newer car, they had “alternators” which produced AC current (which was then rectified to produce DC)

Therefor the OP believes anything called a “generator” is creating DC current internally.

I see how the terminology is confusing….
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Old 11-15-2021, 12:51 PM   #13
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Originally Posted by pasdad1 View Post
I....
I see how the terminology is confusing….
There is a lot of that going around. Waiting for Motor Trend to be called heat engine trend.

Heat engines convert thermal energy to mechanical work. Turn a generator and electricity is produced.

Supply electricity to a generator and it becomes a motor. A bad thing if it not designed for that.

I have an obsolete expertise in variable frequency motor generators. A bad thing happened because I did not understand control system. I became an expert. These days variable frequency motors can be powered inverters.

So are inverter generators worth the higher cost for your RV?

Marketing BS aside, my $88 1000 watt HF 'construction' generator gets the job done for charging batteries while running a residential fridge and TV. My 2200 watt inverter generator that I got at the same price as a same rated construction generator will run one A/C. It also gets the job done for charging batteries.

Also Have a 6500 watt Onan. Gets the job done especially if you need to run 2 A/C.

Confusing terminology can be used by the marketing department to get you to pay more.

Last night I after reading about THD I measured the PF of my 30 watt $100 Chromebook. PF = 0.51. The grid is not affected. Neither is any on my generators.

There are people I know who call me dad. Would I run their gaming computers on any on my generators?

Let me answer it this way. I have a flip phone, an vintage MH, vintage TOAD and a vintage sailboat.
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Old 11-15-2021, 04:32 PM   #14
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It sounds like you are all set, none of this technical malarkey to put up with. I like messing with the new technology but when it doesn't work I wish I still had the old 1950's auto "technology".
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