# Portable generators and elctronics



## Matt88-8 (Dec 27, 2018)

So, I've always been told never run electronics off of run of the mill (non inverter) generators. Makes sense, power surge or Hertz change etc..

BUT. Last time I moved my router I noticed the tag on the back that lists its inputs. My TV is the same, so is my laptop charger, chromecast, cellphone etc... 
All of them say the same thing:
Input: 100-240V 5050-60hz 

So, if the power adapters are capable of such a variable input what about generator power is dangerous? 

My generator isnt fancy, but I've checked with my multimeter and voltage has never gone below 118 or above 122 during normal use. Would the Htz cycle vary more than 10 htz?

Anyway, could somebody please explain why generators are dangerous for electronics? I'm not doubtful, just genuinely curious.


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## Matt88-8 (Dec 27, 2018)

Here is an example


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## tabora (Sep 6, 2018)

Matt88-8 said:


> Anyway, could somebody please explain why generators are dangerous for electronics?


These days, with most electronics running off A/C adapters that create D/C voltage for internal consumption, it's much less likely to cause damage to the devices themselves. The A/C adapters CAN be damaged by low/high voltages outside the specified range. The only issue usually comes if the AVR (Automatic Voltage Regulator) in the GenSet goes completely crazy and drops or browns out a hot leg or starts allowing 300V+ out to the outlets if the governor sticks or something else malfunctions to affect the output. I have a whole-house surge protector at the meter/generator inlet to protect against the latter of those conditions, and a Dranetz Power Disturbance Monitor to alert me to the former.


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## RedOctobyr (Aug 8, 2018)

Some of the risk to items you're running comes from the jagged shape of the sine wave. The voltage and frequency can be correct, but non-inverter generators will still produce a lumpy sine wave. 

A cheap inverter will make something even worse, a "modified sine wave", which can be just a square wave with the edges rounded off. You want a "pure sine wave" inverter for anything sensitive.

As I understand it, the poor sine wave shapes are particularly tough on electric motors, and can make them run hot. Anecdotally, I've heard people say their modern furnace would not run on a non-inverter generator, but I don't know the exact underlying cause. Maybe their voltage was off, etc.

As long as the risk is mainly to a power supply, that wouldn't worry me too much, as they can be replaced pretty readily.


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## Matt88-8 (Dec 27, 2018)

Interesting. So the biggest danger is to the power adapters and not the devices?
That would change things for me, as these adapters can be pretty cheap.

As far as the sine waves, I know cheap inverters cause issues, my water heater(gas) wouldn't even turn on with an inverter. 
What causes the generator to make "lumpy" or uneven sine waves? Are the windings imperfect or is it from surges in the engine??


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## tabora (Sep 6, 2018)

Matt88-8 said:


> What causes the generator to make "lumpy" or uneven sine waves? Are the windings imperfect or is it from surges in the engine??


 It's really just a matter of how the power is being generated in the generator (alternator) head vs an inverted (regenerated) sine wave. Read more here: https://yamahaef2000is.com/conventional-generators-vs-inverter-generators/


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## RedOctobyr (Aug 8, 2018)

(Sorry, tabora replied while I was writing)

Hopefully tabora can address that. I don't know if the main/only risk is to power adapters. I don't know if there is also risk to the device itself. My hope is no, but I don't know. Measuring the adapter output voltage with an oscilloscope would show if the output changes when running off a generator. 

This is a nice page with sine wave comparisons. The last example is from an inexpensive generator. A little bit further up is the EU2000i inverter generator's output.
Power quality from various backup devices

I'm not an electrical engineer, I don't know the explanation behind why non-inverter generators produce an electrically-dirty output. It's not because of large-scale engine surges, like the continuous RPM actually going measurably up or down, such as from a flawed governor on the engine. Those wouldn't show up on such a small scale, and they'd produce frequency changes, rather than 60 Hz. 

Though actually, my Generac had you set the governor to 61-63 Hz with no load. As you added a load, it would slow down to around 60 Hz. An electronic governor, vs mechanical, would have tighter control of that. Even an inexpensive (modified sine wave) inverter will at least produce a constant 60 Hz.


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## santomar (Sep 5, 2018)

Dear ..Non inverter generators usually runs on basic concept i.e. they run on fossil fuel that is diesel or gasoline, which produce electricity by powering the motor attached to the alternator. Household items as you mentioned in your post requisite 120 volt at 60 Hz.
To gain constant output it is must that the motor must run at the constant speed that is 3600 rpm usually.If the engine's rpm will fluctuates the frequency will also vary.


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## Osviur (Sep 7, 2015)

Hi,

The quality of a voltage sinewave is just a matter of production cost.

To produce a voltage that varies as a sine function, a senoid, it is necessary to “cut” the stator conductors with the magnetic lines coming from the rotor in a continuously varying way, as similar as possible as a sine function. 
To do this, the stator windings must be distributed in the slots in such way that the rotor field, when is approximating, induces a few volts that will be incremented as the field increases and the turns per slot increases too. This implies that the slots are not full filled with wires and the space is not used at its maximum capacity. 
As a consequence, in a well designed full cost generator, the iron used is more than that used in a low cost gen and the same is with the copper used.

More iron and copper means more volume and weight, and COST. 
The sine waveform has been selected because its continuously varying value, without jumps, avoid electrical reactions proportional to the voltage change speed. A clear example is the reaction in an ignition coil when the points open and the magnetic field collapses.

Square waves are not bad when the circuit is designed to work with them, the mentioned AC adapters work with 80,000 to 150,000 Hz , square waves inside its circuits, but their input diodes will withstand about 600 volts AC (840 peak volts) easily overcomed by a series of peaks coming from a “modified sine wave” inverter or a cheap generator feeding an inductive load like a transformer or a motor, some of these peaks can force current against a blocked diode and cause a short circuit in the diode bridge destroying it.

Along with the basic frequency (fundamental) other undesirable freqs are generated. In example a 60 Hz genset produces a 60 Hz (cycles per second) fundamental frequency and multiples like 180, 360 or 300, 420 stc. Depending of the gen design, using different kinds of windings, stator and rotor, the waveform can be very near to a sine function at only 60 HZ, or a deformed wave with sharp edges and flat tops, at 60 + 180 +360 HZ, creating a waveform different from the original fundamental 60 HZ sinewave.

This deformation is known as harmonic distortion because the triple freq, the sixth or the fifth and seventh freqs are known as harmonics, third harm, fifth harm etc.

All of these undesirable frequencies are mixed giving a deformed, distorted, 60 dirty HZ. Feeding a motor or a transformer with this kind of power will overheat them because the higher freqs will induce higher losses in the iron cores, overheating them. A motor speed control using phase control will fail due to the uneven form of the wave.
Inverter generators produce trapezoidal waves with variable frequency and convert them in beautiful sinewave clean power. 
Grid power come our homes in a very clean sinewave from full cost, well designed generators, without the need of use inverters to get good quality power.

For all you participants in this Forum, have a VERY HAPPY NEW YEAR 2019


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## Osviur (Sep 7, 2015)

Hi,

I have found an old thread: "Total Harmonic distortion Filter" in which I posted some pictures related to the waveform found in some devices and in the mains. (May 24 2016)

First picture shows the 220VAC from the grid.
Second from a sine wave UPS output, similar to a quality pure sine wave inverter.
Third, fron a "modified sine wave" cheap inverter. 
Fourth, waveforms (in drawings)


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