Electric motor overspeed and grid backfeed

[BruceM]

Yep, double wall, superinsulated with in-floor heat works great with a 32'x4' DIY solar hot water flat panel collector and in ground, DIY EPDM lined 800 gallon drain back insulated storage tank. 
Same tank does my domestic hot water as well, with 180 feet of 1/2 copper (4 coils in parallel) as heat exchanger.  I heat the house direct from the storage tank.
About $30 year for house/domestic HW heating via backup propane in Dec. and Jan..  5600 feet elevation in AZ.

[Jens]

About $30 year for house/domestic HW heating via backup propane in Dec. and Jan..  5600 feet elevation in AZ.

NICE !!!!!

[buickanddeere]

  That is how all those d&mmed wind turbine around my place are designed.

[glort]

I have been doing this for some time now.
Just in the process of setting up a Ruggerini 12 Hp with a 5.5 hp 3 phase 1440 motor. Going to rig up a couple of 12v alternators as well to make it more versatile.

Presently I use a 3 Phase motor rather than a single phase. Because of this the start isn't totally self sufficient as the motor needs to be spinning to start off the single phase power it's hooked up to. The ruggerini has a starter motor bigger than my car so I won't have to worry about this in the future.  I now get the motor spinning a bit so when I hit the switch,  the thing will kick in and not just freeze. It's a bit like winding a CS up to get it over compression. 3 Phase motors will run straight off single phase with direct connection to power ( no caps) once you get them turning fast enough so they catch up with the phase shift of the 2 poles.

In any case you are going to have to use a substantial motor to get a CS spinning if that's what you are thinking of. l I have tried a 1.5 Hp motor with a 3"  pulley onto the flywheel and it wasn't nearly enough. I don't know what your electrical system will take in the US but starting a motor under load here more than about 2.5 HP on normal household single phase isn't going to happen unless you like replacing fuses a lot.
When  the motor is up to speed, I drop the de comp lever on the china Diesel and off it goes. I have the throttle set to the right position and it kicks in straight away. The engine speed is not that critical. As soon as you go about 10% over synchronous the motor will generate. The more you open up the engine the harder it lugs to make more power as the motor resists.
I have mine set at about 2.2 Kw which is comfortable for the engine and not too noisy either. With the Ruggerini I'll be able to generate the full 3600W a standard circuit will take here. with the 5.5Hp motor that's about all it will do in thi configuration anyway as the slip makes it impossible to output the normal motor power.  As a generator they say figure about 500W output per HP. I think that's a bit low but it is a safe working limit even if a bit too safe in my book. You certainly shouldn't overload anything at that rate.

I have found the synchronous speed thing on motor generators is a lot over exaggerated as well.  If the engine is driving the motor and you do connect the power when it's out of sync, you get a bit of a knock as they do sync up and the motor position locks and that's it. No different to the motor already running and having a load dropped on it like from a compressor or something.  No explosions, smoke, broken bits or anything else. It's just a bit of a load dumped on the circuit and there is an amount of electrical elasticity in that, it's not the shock of throwing a lump of concrete in a flywheel.  If you ran a belt with a tensioned, that would allow all the movement you would need for a smooth sync up as long as you are not 1000 rpm off.
I understand the idea here is to use the motor as a starter and avoid this but just pointing out that engaging the motor out of sync with it being somewhere in the ball park is not a big deal at all. May be different for proper generators but for motors I have not seen anything at all worrying.

Please, for god sake, no one start on the " safety" garbage of the grid going down and capacitance on the line and other entirely theoretical CRAP that would never happen in real life. Anyone that has DONE a motor setup like this would know how sensitive the motors are to dumping loads on them and crashing the field. No load would have enough capacitance to compensate it on start-up or running (Which is effectively neutralised) and the dump load it imposed on the motor especially when it was probably a good distance away and there was the resistance of the line itself to over come. With that much capacitance the thing wouldn't run properly and would probably burn out.  Experience with this set up easily shows why the theory is so flawed no matter how parroted it is.

Even if it were possible, you take the risk you will die every time you get in a car but you still do it. The chances of you lighting up miles of power line and all the neighbours loads as well as your own with a small induction motor are less than you winning the lottery or dieing in a car crash getting to buy the ticket so lets all stop with the over pedantic garbage on that subject before it starts.  In any case no one will convince me it is a real and credible danger so save your breath trying because it will not change my mind or what I do. When someone shows me a documented test that proves me wrong, I'll believe it possible.  Until then, to me it will be nothing more than over pedantic safety garbage. There are all sorts of dangers with what we do from exploding flywheels to fuel fires, electrocution etc.  but we don't over exaggerate and blow them out of logical proportion so I don't know why this has become a pet cause of the internet fear mongers?

Now, that said, I keep the safety sissy Nazis happy by running my back feed through a proper solar inverter.  The motor is wired in a C2C configuration for excitement then goes through a Diode bank to rectify it to DC and then into the solar inverter. This way I can use all 3 phases from the motor instead of just 2.
On that, I have tried loading motors on just 2 phases and I could not get any problems when trying. The motor did not over heat on the 2 windings used, it was not unbalanced mechanically and after hours of testing I could not find any reason why the setup couldn't run indefinitely on 2 of the 3 phases. I came to the conclusion in fact that as the motor was only running 2/3 of it's output, It would take effort to over heat one because the fan is providing more than 33% extra cooling to the motor and the dissipation of hat there is would be dropped into a larger heat sink.  If one had a big enough motor, say a 10 HP, then 2 of the legs would probably generate the max loading the fed circuit could hold, depending where you are and the ratings of the circuit. Here a normal single phase 240V household circuit is 3600W,

If one wanted to use a motor to start the engine, a single phase motor would have to be modified, assuming you don't have 3 phase power or a motor.  A 3 phase does need external mods/ setup  as well externally but there is no plug and play solution to the starter/ generator setup either way.  I guess you are trying to get away from hand cranking but in the end it's probably easier if you can manage it. If not, well you'll have to do a bit of wiring and switching.
The capacitance on a single phase would normally be disconnected as it's on the start windings so I think you would have to switch that and make sure it was a run cap rather than a start.  You would also need some capacitance on the run windings same as a 3 phase which would have to be switched in after the engine was turning the motor I think. It may be possible to permanently wire the cap to the run windings as the thing will only work as a motor briefly then it will be in generator mode. You shouldn't have any problem with over heating for a brief period with the thing having a cap in motor mode.
You can look up the tables to see what size cap you need for what size motor and phase.  I briefly played with a single phase motor to see if the theory  did work and as it did first time out, it was clear the 3 phases offered a lot more flexibility with the set-up and were able to be had in much better outputs so that is what I have got real experience with.
You can potentially run 3 separate legs at 1/3rd output, Combine all 3 into a single phase or run it as a normal 3 phase to power other 3 phase requirements or direct for backfeed.

The way I see it, your biggest issue is the start up. You will have to have a motor of sufficient size to spin the engine and it will then have to be wired in such a way it can work both as a motor and a generator.  this will require Caps added and some mods to a single phase motor or a starting control box for a 3 phase. Too tired to think it though right now but offhand I can't see why a C2C wire up wouldn't work. the advantage being that it should work for start up on single phase and combine the 3 legs as a generator for a total output of the motor rather than a partial one. It would also give the motor more sensitivity to grid failure if the caps were under rated a bit which you could get away with in this case as it's only for phase alignment not excitement of the windings.


Entirely Doable, no question but not simply a matter of hooking up an engine and motor and throwing the switch.

[vdubnut62]

Ok I'm with Casey, what kind of li'l critter do they squeeze to get synthetic oil?? Yes, we know what it's for, what it does and the benefits therof, but from where does it originate?
Unicorn farts? Dragon tears? Listeroid droppings? Yes I said droppings, not drippings.
Ron.

[SteveU.]

Good post glort. Thanks for the work writing this up.

Ron on the engine synthetic oils base stocks . . . take your pick.
Some proudly made of only natural gas. Some care about this.
Some proudly made only from plant oils components. Even more care about this.
Most synthetic engine oils are made from dino HC's chains.
I only care what it does for hot running air-cooled engines. A high percentage of the engine's excessive heat IS oil transferred to the cases, and/or oil/air cooler. Turbo-charged engines have a very HOT oil lubricated/COOLED turbo bearing!
Regardless of the base source these are said to be terrible as used-oil compression engine fuels. The molecules are too stable and cause smoking and deposits building up when used as fuels.

S.U.

[glort]

Like many things, I go against the grain ( especially the internet type) when it comes to oil.

I run my truck on supermarket own brand oil or whatever is on sale at the time. Although I do try to stock up when it is on sale.
Even supermarket brand oil is about 5 grades above what was specified for my truck when it was built 24 years ago. What is looked at as cheap shit the high and mighty wouldn't touch now would have been some miracle wonder oil they would have paid $100 a container for back then.  Engine is the same, it's requirements haven't  increased so as far as it's concerned, the supermarket grade stuff on up is liquid gold.

Instead of buying the $70-80 synthetic, miracle in a bottle oil, I rather buy the $15 stuff and change it twice as often.
It's not the oil breaks down, it's the acid's and crap in it that builds up. Expensive oil won't change that but keeping Fresh, clean, even cheap oil in it will.

The thing I think is often overlooked is Filters. My truck runs 2 Full size filters. Many vehicles these days are lucky to have 1/4 of the filtration mine does and unlike some who only change the filters every 2nd oil change, mine gets done every time. I saw a report some time back done by an oil company that actually came to the conclusion that changing the filters was more important that he oil they concluded from their tests that the filters declined in performance very quickly especially given how small they were these days and changing the filter half way through the change cycle could do a lot to help the engine stay clean.

The other thing why I am not a big proponent of trying to find the best oil out there is modern engines. Even not so modern.
My Father has a Subaru Wrecking yard in the country. I have personally seen 3 engines at least 15 yo with over 500K km on them that have still had the hone marks in the bores when they were pulled down.
It is very rare for one of these engines to actually " wear out" and it's sure as hell not because they have been fed synthetic oil all their lives and looked after. The complete opposite is the case 99% of the time!
Usually the engines get cooked because they loose coolant and the owners just want to drive them up the highway another 50 KM to get home.  They NEVER make it.
Normally the engines are OK if the head gaskets are changed and they haven't been overheated to the point the ally heads have gone soft.  Some are driven till they weld themselves together.
It is rare though for an engine just to become too tired and loose compression/ power or whatever.

The other thing is Synthetic oil doesn't prevent mechanical failure in parts that may have had faults or defects. Different things in an engine may let go due to fatigue rather than wear which necessitate a pull down or rebuild. that to me pretty much makes the investment in synthetic oil a loss.

I don't think the loads in a lister are anything remarkable especially considering the engine speed and the very low HP/ displacement ratio. Most 1.4L vehicle motors these days will put out closer to 100HP, even in diesels, not 6 hp!  Stresses on loads on those are going to be magnitudes higher than with a 650- 1000 RPM engine with the lowest HP/ CuI ever! :0)

Myself, I can't think of anywhere in the engine that synthetic would be better than normal mineral oil. To think it would be  would also assume the mineral oil which is now about 50 grades above what the engine was designed to be happy with when it was released was inferior. No way is that the case. 

For me, fresh, clean, cheap oil however many grades above what the engine was specced for originally in low demand engines like this will actually do more for longevity and trouble free operation that expensive synthetic run longer to get ones moneys worth.

[SteveU.]

Sorry form this "oil" topic drift came off of another topic thread Mr veggie.

glort the engines I have learned to exclusively use the 100% systhetics in are the small airclooled once past fully broken in. These only have .3 to 1.5 liter oil capacities. And most do not have full flow oil filters. Cheap to use the synthetics. Dump out with the contaminants at ~100 hours and 4X, 6X the engines usability service life's.

On the bigger watercooled with full flow filtration I do exactly (almost) as you do. Use the cheapest spec grade of straight unblended dino/mineral oil and just change out, along with
the filter at the lower intervals schedules.
Where I differ is I use a mid-price grade filter. DO change it each and every time. And still put in 1/2 to 1 quart of my favorite stocked synthetic (Castrol) just as a make me happy, assurance. Only needs enough for wearing metals surface coatings. Be damned about claimed oil additives incompatibility's. They are required to engineer for non-conflicts to make spec grade certifications.
I pass on the super filters, and super oils, and just buy more oil/filter and change more often for a far lower overall cost. And better service life results.

Scary, current spin? The new consumer grade Briggs & Stratton engines are offered up the the users as "No oil changed needed anymore", "Just check and top up, for the full service life of the engine" And this is on up to $1500 USD pieces of equipment's. Pay for the $2000-2500. version then you get the B&S engine's installed that still "need" oil changes.

Sheeple madness abounds
Steve Unruh

[Henry W]

Oil topics were discussed years ago on this forum. There is a wealth of info if you search.
I've put on thousands of hours on air cooled engines when I was in the lawn care business and I seen what a good group 4 synthetic oil can do in protecting engines. One of the most noticeable things I've noticed is less valve train adjustment on Kawasaki v-twin engines. The Kawasaki v-twin engines that was on my equipment ran hot and conventional  Dino oil turned dark brown much quicker than a good synthetic. So, I've learned that conventional broke down much faster.

Now with liquid cooled engines I've had no problems with Dino oil.

The bottom line is run the recommended oil from the manufacture.

[glort]

i have some experience with engines in the lawn care property Maintenance business adn I saw very few that actually wore out.  The majority were replaced through damage.  Hitting hidden objects, falling off trailers or utes, running out of oil, being cooked through not having debris/ clippings/ sawdust removed, running 2 strokes with no oil in the fuel and so it went. Few engines ran their complete lifespan where wear was the problem rather than damage.

As such I used to tell people, especially those that had a history of gear abuse, just buy the Chinese motors because the Honda's etc will not last 4 times as long as they would have to in order to justify their price and you are going to kill them before they wear out anyway. It was reality rather than a sales pitch and they all knew it. I sold a ship load of those china engines and had Very few non damage related problems.

One thing I find is a unsubstantiated but frequently raised issue with Veg oil use as an example is shortened engine life. Thing is, whenever I have said " This is the engine in my vehicle, how long should I get out of it? " the reply is always that it varies as well known it does. My question then is, how do you then conclude using veg will shorten engine life if there is no average number to begin with to know if it's life was shorter or better?

Scary, current spin? The new consumer grade Briggs & Stratton engines are offered up the the users as "No oil changed needed anymore", "Just check and top up, for the full service life of the engine" And this is on up to $1500 USD pieces of equipment's. Pay for the $2000-2500. version then you get the B&S engine's installed that still "need" oil changes.

I don't think many people in the domestic market change the oil on their mowers anyway. they have probably been running without an oil change for the most part for years.  I have heard of a lot of people that drained the oil out of their cars and put it in the mower.... Hmm, that's not cheap arse or anything is it??

Personally I wouldn't touch Briggs with a barge pole anyway nor Tecumseh. I have pulled both of those engines many times straight out the box and pulled them apart.  The way they were built and the lack of quality control was Criminal. I remember one Vertical 5HP IC engine that had so much casting flash in the inlet and exhaust ports just under the valves I doubt there was enough room for gasflow beyond 1/2HP. It was common to have flash blocking the ports but not to that extent. We cleaned them out with a grinder as a matter of course.
Bloke I worked for pulled all the Briggs motors down before he let them out the door to the contractors. People thought they were great engines and insisted on them. He hated the things and for good reason. They were shit quality and rough as guts  as well as parts here being ridiculously expensive. As he pointed out to me one day, He could buy a full set of pistons and rings for his car cheaper than he could get a single piston and rod for a 5 HP Briggs.

My father has a Kawasaki twin on his newish Ride on. One day it wouldn't go. Mechanical guru that works for him couldn't figure it out.  Rang dealer, " Have you changed the oil? " Ummm.
Changed it and thing fires right up. Won't work if the oil gets too black.

Mate of mine about 4 years ago bought himself a new quarter million dollar Iveco Truck.
9 litre engine, 14L sump. First oil change, 50,000 km. Subsequent changes, 100K km.  No dipstick. You get an oil level reading on the star wars LCD speedo/ dash panel the size of a computer monitor and is touch screen. No top up should be required between services. And it didn't appear to use ANY oil between services right from new!

Long as you take the thing to an Iveco dealer for an oil change by the required mileage, they guarantee the entire power train for 1 Million KM.