Festool AC/DC

[jmarkflesher]

Some of my Makita tools are marked ac/dc. House current is ac. I think my generator puts out dc. I have been told in the past  that tools not built for ac/dc will run off of dc but will degrade the motors more quickly. Is this true ????

 

[tjbnwi]

Your generator is AC, it may have a DC tap for running/charging DC items, normally a 12-14v output.

Tom

 

[Administrator_JSVN]

I don't believe there would be an issue with running a tool off of a generator, which as stated produces AC current.

Rick Christopherson posted about this once before and has more of an electrical engineering background. May be worth a message to him if you have concerns.

http://festoolownersgroup.com/festool-tool-problems/well-well-well-never-thought!!/msg109493/#msg109493

 

[jmarkflesher]

Thanks for the info. I don't know about sine waves but there were plenty of waves down the jersey shore. That's why I'm running off a diesel generator. No damage at my house but power still out. I still have 350 gals of heating oil in basement to keep it running. MARK

 

[johninthecamper]

ohms law is not variable,except within itself.so you can run anything you want from anything you want as long as ohms law is followed,you need a certain amount of amps to run cool enough,that is dependent on the original source,into the restance of the cord,which is depending on the gauge and length, not from the outlet but the breaker,times two for the rereturn or neutral ,the machine will try and pull what it needs in watts(voltsxamps),if it can't get enough, it will slow down and get hot,so as can been seen there are many factors which come into play.what it really boils down to is use as fat as cable as can be used for the various nema connecters whether 15,20 or 25,using as short as cable for the task.if you try and run ac or dc switched around in theory it could be done, easy on paper, but to buy the U L stuff would be almost nasa in budget

 

[Sparktrician]

I would first check with the manufacturer of your generator to find out whether the generator's output is true sine wave, modified square wave or square wave.  Many things will run on the square wave output, but sensitive electronics often object strenuously and some will actually let the Magic Smoke escape if subjected to square wave. 

 

[Nick C]

I concur with Sparktrician. The difference between sine wave, modified sine wave, and square wave is significant, even though they all qualify as alternating current. Without getting too technical, a good rule of thumb is that the more complex and sophisticated a device is, the more likely that it will be harmed by an improper wave shape. I would be concerned about two potential problems with my Festool motors: Excessive heat, and damage to the variable-speed circuitry. Pure sine wave is the best, modified sine wave is marginal, and I would not "push" a tool very hard if I had to use this, and square wave would be out of the question. Regarding the comment about Ohm's law, we should remember that the line voltage and current are varying, reversing polarity sixty times per second ( in the US). But the power the tool is delivering, and therefore drawing, is relatively constant. Since power equals voltage times current, how is this possible? Clearly, the motor has an averaging effect that "smoothes out" the varying voltage and current, resulting in a constant power (watts) output. This is made possible by good motor design, which can be defeated by an input power source that is different than anticipated.

 

[jmarkflesher]

I'm using a friends internet so just reading some replies. Is there a devise to plug into a generator to see if output sine is true , modified or square? Generater is French or Italy made with Yanmar diesel. MARK

 

[Sparktrician]

I'm using a friends internet so just reading some replies. Is there a devise to plug into a generator to see if output sine is true , modified or square? Generater is French or Italy made with Yanmar diesel. MARK

You can use an oscilloscope to check the wave form.  There's a decent discussion of pure sine wave vs. modified sine wave here.  There is a plethora of images regarding waveforms here.  There's also a very good discussion of the waveforms here.

[smile]

 

[Laminator]

Just a comment, I seem to remember some portable welding machines (Gas or diesel powered) output DC.  Its been a long time since I last ground slag out of a stringer bead on a pipeline but I think the grinders had to be rated for both AC/DC  electricity.

 

[Nick C]

I would ask a commercial electrician to do this. There are portable instruments called power analyzers, but they're quite expensive. Make sure the voltage is ~120VAC, the frequency is 60Hz, and the waveform is sinusoidal. An oscilloscope could be used, but that could be tricky--you might need an attenuator to allow you to measure the generator output at a reasonable level, without overloading the test instrument. BTW, Honda makes some very nice portable generators that play well with Festools--I use the EU3000is all the time.

 

[EdL]

Just a comment, I seem to remember some portable welding machines (Gas or diesel powered) output DC.  Its been a long time since I last ground slag out of a stringer bead on a pipeline but I think the grinders had to be rated for both AC/DC  electricity.

Correct, many years ago portable welders were DC only. I know Milwaukee used to make a lot of tools that were ac/dc.

A friend has a DC only welder/generator, its powered by a Chrysler flathead 6cyl industrial engine, it's got to be early 60's vintage.

Ed

 

[jmarkflesher]

Just got internet back Friday. It seems my router/modem was damaged by the surging of the generator??? {this was on a surge protector}  They were unable to reconfigure it.  All day today trying to figure out problem with the washing machine. Appears electronics were damage. Need a new control box. Generator or not. You be the judge. MARK

 

[peter halle]

Generators  and inverters are a touchy subject to me and honestly I have to say that using them is a risk you take.  Years ago I bought an inverter for my truck.  It fried my Dewalt battery charger.  I ended up buying a new charger and inverter and that one works and also works with my Festool chargers.  My ancient one circuit generator acts nicely with my electronics but I suspect that I am just lucky.

Peter

 

[Rick Christopherson]

That's why I'm running off a diesel generator.

If it's a diesel generator, you are pretty much guaranteed that it is a true sinewave output. Inverter outputs come from smaller home type generators.

 

[Sparktrician]

Just got internet back Friday. It seems my router/modem was damaged by the surging of the generator??? {this was on a surge protector}  They were unable to reconfigure it.  All day today trying to figure out problem with the washing machine. Appears electronics were damage. Need a new control box. Generator or not. You be the judge. MARK

You may want to consider the use of a whole-house surge protector installed at your main breaker panel.  The SYCOM SYC-120/240-T2 is one such unit that works quite well. 

[smile]

 

[Nick C]

Lot of confusion here. A true sine wave output is created by an inverter, which is a device for converting DC to AC. A so-called inverter generator employs a three-step process: The engine (gas, diesel,... it doesn't matter) drives an alternator whose output is three-phase alternating current at a high frequency (could be 20-30 kHz). Next, this AC output is converted to DC. Finally, the DC is converted to single-phase AC, at the desired voltage, and frequency. This final output is "pure sine wave" just like what comes out of the wall socket. The "inverter" is the internal component that converts the DC into the AC. (Stand-alone inverters are often used to convert 12V DC from car batteries to 120V AC). This type of generator is more complex, and therefore more expensive. A lot more expensive. In addition to the well-behaved output, such generators also allow the engine to run at a speed corresponding to the load, rather than having to maintain a constant speed as is the case with non-inverter generators. If the average load does not require full output from the generator, this feature results in reduced fuel consumption, less wear and tear, and less noise. In addition to not damaging the appliance that is plugged into it! IMHO, our expensive Festools deserve no less!

 

[PaulMarcel]

You may want to consider the use of a whole-house surge protector installed at your main breaker panel.  The SYCOM SYC-120/240-T2 is one such unit that works quite well. 

[smile]

That looks pretty good; trivial to install, too.  I've lost more than $80 of equipment to surges when we had the main service flicker on and off several times before staying off.  That's worth the $80 to eliminate that possibility.  Thanks for the link...

 

[Sparktrician]

You may want to consider the use of a whole-house surge protector installed at your main breaker panel.  The SYCOM SYC-120/240-T2 is one such unit that works quite well. 

[smile]

That looks pretty good; trivial to install, too.  I've lost more than $80 of equipment to surges when we had the main service flicker on and off several times before staying off.  That's worth the $80 to eliminate that possibility.  Thanks for the link...

There's an even better price here, too.

[smile]

 

[Rick Christopherson]

Lot of confusion here. A true sine wave output is created by an inverter, which is a device for converting DC to AC. A so-called inverter generator employs a three-step process: The engine (gas, diesel,... it doesn't matter) drives an alternator whose output is three-phase alternating current at a high frequency (could be 20-30 kHz). Next, this AC output is converted to DC. Finally, the DC is converted to single-phase AC, at the desired voltage, and frequency. This final output is "pure sine wave" just like what comes out of the wall socket.

Nick, I am not sure whether you are the same person that thought they were correcting me once before on this topic, but your information is off a little bit; in part due to marketing and in part due to misunderstanding.

Inverter generators are limited to smaller outputs due to the cost of high-power rectifiers and switching transistors necessary for the output. I do see that they are now beginning to make some diesel powered inverters, but historically, diesel powered generators have previously been industrial systems with electromechanical generators.

The high frequency you speak of is not on the AC bus, but is the carrier frequency on the DC bus side of the inverter. The mechanical alternator doesn't need to be high frequency because the output is converted directly into DC power. The high carrier frequency is part of the PWM process for creating the output waveform. The higher the carrier frequency with respect to the target output frequency (60 Hz), the closer the output waveform can be approximated to a true sinewave.

It's the same principle that is used in digital-to-analog converters that convert your MP3's and CD's into audio waveforms. It is taking a digital representation of the signal and simulating an analog signal. But it is nevertheless, still a simulation of the true sinewave signal. Depending on how good the output filter is, there will always be small remnants of the high carrier frequency left behind. It is these remnants that can interfere with Festool MMC electronics.

The term "True Sinewave" is a bit of a misnomer that confuses people. The term exists to separate it from the term "Modified Sinewave". The "true sinewave" has the basic shape of a mathematical sinewave, but it still contains the harmonic distortions of the carrier frequency. In other words, it is not a "smooth" sinewave. I believe that in order for an inverter to claim "True Sinewave" output, these ripple distortions must be below 3%.

I found the image below that shows a "True Sinewave" output from an inverter displayed on an oscilloscope. You can see the choppiness of the core sine wave shape. What looks like "fuzziness" about the sinewave is actually the harmonic distortions of the carrier frequency. The output from an electromechanical generator is a true mathematical sinewave, not just an approximation.