Inverter to run the Tormek.

[frank4570]

 I have a used Tormek 2000 which functions perfectly. I need to run it with my vehicle electrical system if I can. If anybody can tell me what size invertor, which particular inverter, if I need to run cable directly to my battery, etc etc.... I would appreciate it. I will probably run the sharpener for a couple hours, then drive a couple hours. Portable sharpening service.

Thanks!

[Mike Fairleigh]

Interesting question, so I set up a little test.  I have a new T7 system, whose motor is rated at 1.65A @ 115VAC.  To make sure the motor didn't exceed that (i.e., to make sure the ratings on the motor were reliable for use in calculating for an inverter), I ran the machine under different conditions while monitoring the current with a Fluke 289 DMM and a calibrated Fluke i410 current clamp.

Running with a wet wheel and no additional load, the motor consumed 0.9A.  I then simulated a usage load by bearing on the wheel with the coarse side of the stone grader, with a lot of pressure, such as I'd use when re-grading the stone.  The maximum current observed was 1.35A and I could only make it go that high for less than a second.  My household voltage runs around 120V, so I would say the 1.65A @ 115VAC rating on the data plate is spot on accurate, and maybe a tad conservative.  (Increased voltage = decreased current, all else being equal.)

So, let's use the rated 1.65A for inverter calculations.  Inverters are rated in watts, not amps.  1.65A @ 120V is 198W.  SO - in theory, a Wal-Mart 300W inverter running from your cigarette lighter plug would give you plenty of capacity with a 33% margin (and by the way, margins are GOOD things where inverters are concerned - never use one that barely meets the load requirements).

But there's more to it than just watts.  There's also the quality of the power to be concerned about.  Small AC motors are more forgiving about power quality than a lot of appliances (cheap inverters can actually destroy some types of electronic devices), but it's still something to be aware of.  AC equipment is designed to run on "true sine wave" power.  Virtually all cheap inverters don't produce true sine waves; they produce an artificially approximated sine wave.  Depending on the manufacturer, they'll call it a stepped sine wave, a PWM sine wave (hoping you won't look up the definition of "PWM"), a square wave, or a "stepped approximation to a sine wave."  They all mean the same thing.  For your purposes, the important point here is that the cheaper the inverter, the less it's power appears as a true sine wave to your motor.  Again, electric motors are more tolerant of this, but if this is going to be used frequently (commercially?), then you might do your machine a favor by spending more for a better quality inverter.  You don't need that much capacity - again, 198W is a small inverter - but by getting one with some extra capacity with a better sine wave, you might find that you can run another small appliance or two with it and be better off.  A better quality unit will also run cooler, more efficiently (i.e., run your machine longer between needing to re-charge the battery), and generally last longer.

There are several decent brands of inverters.  Xantrex and Tripp Lite come to mind, but there are so many companies making them now it's hard to keep up with them.  Another option, albeit an expensive one, would be a small inverter generator such as the Honda eu2000.  At 200W you could run all day long on a small tank of gas.

[frank4570]

That's pretty great info Mike. This machine will be used for my scissor sharpening service. So, in the future will be a truck camper, air filtration system, air conditioner, and proper generator to power the whole thing. But right now there is work to be done, and an inverter will get me going just fine.
Your response is really helpful, thanks a lot!

[RobinW]

A point to note, and I suggest that this should be addressed Tormek, but in the industrial world, if you use a motor on an inverter or variable speed drive, then different bearings in the motor are required. This is due to the irregular waveform from these types of drive causing spurious eddy currents in the motors eg along the shafts, and these will find the weakest path to earth, usually through the bearings and so ruins them. They get round this by using specially designed insulated bearings.

The ideal inverter would be fixed frequency and fitted with a suitable amount of filtering to get rid of harmonic and transient components and give a supply equal to that off the grid. I regret that I cannot give you any names of suitable inverters as it's some years since I've been involved and there have been major advances over the last ten years, but on this side of the pond I would start off with the big names and see what they have to offer.

[Herman Trivilino]

Is there a way to use a 12-volt DC motor with the Tormek?  It seems that would be a better way to go.

[Rhino]

I have a honda S2000 generator.  I am not sure of the model number.  It is real nice and quiet too.  They also sell a 1000 watt generator which is lighter.  Both of them are about $1000 each.  There are lots of uses for a portable generator.  You should go check one out to see if they are too noisy.  The power out of these things are supposed to be clean. 

If you plan to do a fair amount of portable grinding, instead of idling the truck all day, maybe you want a small generator.  It also powers my other tools such as a drill, small compressor, lights, fan, coffee makers, charge your cell phone etc.  Makes my whole setup real portable.

Just a thought.  I know it is more than what you want to spend.  If I were to work a couple of hours away from electricity, I really would appreciate a generator so I can at least have a fan running and some small comforts of life like a radio. 

Also, I don't think you can power the Tormek a couple of hours without running your car/truck engine.  That would negate any savings.  Your car/truck will wear out a lot faster if you idle it a few hours a day.

[Rhino]

Another argument for a small generator.

Idling a car engine is an expensive way to run an invertor.  Even a deep discharge lead acid battery will only last 100-200 cycles.  The reason they last so long on a car is that they are hardly used.  They are used to start up.  Then immediately, when you are driving, you are charging them up again.

So like life everywhere, running something off batteries (even with an invertor) is a lot more expensive than running off a generator.

The honda generators are small, more or less quiet, use very little gas, and would save wear and tear on your car and/or battery.  I got the 2000 watt model because it is like 10% more expensive and 100% more power.  It is less portable but I am driving around in a car and have a dolly so no big deal.  They are supposed to provide clean sine wave power and be good enough to run a laptop.  So I suppose you will be OK with this one.

I highly suggest you try the honda first.  It is more quiet than other models.  However, it may still not be as quiet as you want.  The discount generators serves a purpose.  However, they are LOUD LOUD LOUD.  My neighbors complain when I fire them up.  That's why I sold it.  It is too loud, even for a contractor (meaning you are not doing it for vacation but to work) because you will annoy your client's customers or your client's neighbors.  Make sure it is quiet enough for your purposes.

[Mike Fairleigh]

Rhino, do you mean the eu2000?  I can't find anything about a Honda generator called the S2000.

The eu2000 is very close to a sine wave, but not quite perfectly true - see http://www.flickr.com/photos/jmschneid/7043367977/.  The eu2000 has also recently been found to generate more RF than virtually every other similar sized unit; not a concern for most users, but it's something to be aware of.  It and most of it's competitors were recently tested in QST Magazine.

But I agree - a generator would be the ultimate, and if I were buying that would be the unit I'd buy, hands down.  I've even considered buying one even though I don't have a strong specific need for it - they're just so darned cute and handy.  But I think the OP is trying to start out as inexpensively as possible, and drawing a couple of amps for short periods shouldn't cause him to have to idle much, I wouldn't think.  Just my two cents!

[Rhino]

KS Mike,

You are right.

I confused the S2000 Honda convertible car with the Honda EU2000 generator.  One is what I have - generator.  The other is what I want - convertible.  I hope you can understand how I got confused and forgive me. 

[Mike Fairleigh]

The S2000 is one very  car!