3 phase line .....

[OkiePC]

I will trade you the electrical and software design (with help from generator experts here) for that goat. Will it eat stickers?

 

[Lancie1]

Nice shop, nice flock of chickens, and a goat for good measure!

This is complicated by two generators, and how to share and control the loads between the two.

Do you only want to consider the 154 KW generator for the load shedding?

What 3-phase voltage do you have it hooked up for (120/208, 120/240, or 277/480)?

How can you control your machines? In other words, does this new control system only have control of switching power to each machine, or can it also interface with the control circuits (lower voltage) for each machine? Tying the proposed Automation Direct PLC into the machine control circuits will be cheaper, but would require tinkering around with some expensive machines and making wiring changes (not usually desirable). On the other hand, only intercepting the power to the machine requires another set of electrically-operated switches (contactors) with the proper control circuits that can interface with the proposed PLC output terminals.

I am sure there are many other questions that will need answers. We here at this site will help all we can, but this is a pretty large project to be doing by the seat of our pants with little information. You really may eventually need to hire an engineering firm to do the design and equipment selection, or maybe a complete design/build job.

Someone needs to alert BobB, the generator guy from down under (Sydney). He probably can design this system during his tea break. EDIT: I sent BobB a Private Message. Maybe he will help.

 

[DEFM]

All right Okie,but I think you'll want this one instead-she's got her op certs and eats stickers

 

[BobB]

Generators can be fairly temperimental things - particilarly tiny ones like these. This size does not handle largish load swings at all well - they are also difficult to control with respect to speed. Even most larger generators (2MVA) can only be loaded with about a 40% load dump - I have seen a 2MVA Caterpillar stall when a 70% load was dumped on it and that is a pretty big V16 engine.
You will need to monitor the load and prevent overload by disabling loads from switching on. Another issue you will have is inrush - if a largish motor starts you have to make sure the inrush is not too large for the generator to handle or it will stall. Another issue is load dumps - if a large load dump takes place the engine may go into overspeed. You will need to check with the generator manufacturer(s) to find out what sort of load dumps, on and off, the generators can handle.
Another issue I see all the time is that my customers expect that if there are 2-3 large generators running in parallel and pretty well loaded, if one generator falls over then dump load off the other one to keep it online - forget it - too late if one falls over and load is quite high - you will NEVER get the load off in time to save the other one.
Hope this helps.

 

[Lancie1]

Thanks, Bob. Do the generator manufacturers offer any type of generator load controllers (load selectors) off-the-shelf, or would something as needed here have to be custom built?

 

[BobB]

Have not seen any but could be around - I generally do all this stuff in the PLC and have not looked for anything else mate.

 

[DEFM]

Lancie,let me go one at a time,not two gennys at once,I pick one based on today requirements.I think just the 125,I'm sure the 54 is too small-hold on -it would be ok except when the potential full load hit,what are the odds that the comp loads,and all 4 cnc spindles start at exactly the same time,well that happens and the 54 squeaks by,throw in one ac and some one faults.so the 125 has to be the one,on days when the shop runs with the ac's and/or the big lathes run.I was hoping not to "mess" with anything now,I was hoping to hook some magical device to a breaker in the panel then to the ac units,hence only the ac would be denied power and only if the genny had a high load demand. I've noticed these demands only last a second or two then they level off. This would allow me to ac the shop.I hope this helps with what I'm tring to do,BTW what part of Bama are you,I had kin in Enterprise,spent summers there.This might start a fight but,roll Tide,Rob

 

[BobB]

Have not seen a magical device at this stage - only maths in a PLC - could be around but have not seen one.

 

[Lancie1]

I am in Florence, Alabama. I was a Tennessee hillbilly until about 4 years ago. Due to poor health, I had to sell out the farm and move to an easier place. Now I are an Alabama redneck, and slowly learning to ride with the Tide.

I was hoping not to "mess" with anything now,I was hoping to hook some magical device to a breaker in the panel then to the ac units,hence only the ac would be denied power and only if the genny had a high load demand.

I think those magical devices are going to be some contactors wired electrically right after the panel breakers, blocking or passing power to whatever electrical load you want to put on your list. Those contactors can be controlled by a PLC program.

I keep visualizing a spreadsheet where a complete list of your shop equipment with the load size can be manipulated to find the best combination of loads for a given number of possibilities. The spreadsheet with some look-up tables and pull-down menus might be the first step, followiing by a PLC program and an operator panel that allows you to select which loads you want to block in given situations.

Now, if the Air Conditioners are the loads to be shed, rewiring the thermostats is not that far fetched, as I did for that Church Heating Project.

 

[jrwb4gbm]

I know this is a PLC forum but, in this case, simpler seems better to me. After re-reading this whole thread a couple of times, it appears that post #7, #8, and #24 make the most sense for this situation. An adjustable current monitoring relay in the generator output along with an adjustable time delay relay to restart the shedded load, the AC units in this case, would probably be adequate.

 

[leitmotif]

Ok I'll explain,when I first started all power in shop came from genny.I got two 400 amp panels.I learned that by putting this breaker here and that breaker over there (referring to the panels),I could make the digital amp meter on genny very even.Throw in 15 florescent light fixtures and a couple small drill presses for countersinking,a belt sander,ect...,and my balance went to-not so good-the genny and the cnc's were not happy.I procured some burial wire and with the back hoe ran a 220v 1p line to the shop.I run all the 110v stuff and a buzz box,also 5hp air comp for when genny not running. BTW some of that is or,as in air comp OR buzz box.The rest of your post is completely over my pay scale.I heard about a batt bank to help with demand and dump,kinda like giant capacitors,-I think.I went with genny because I was out on the street(lease was up,landlord had new tenants willing to pay a lot more),my barn/building was about done -no power,so the 54 was bought and away we went.I'm going to call automation direct and talk to tech support and see what they say.I'll let you guys know what happens,Rob

Rob

With the variations in load in a machine shop I think
1. All lighting except a balanced 3 phase emergency lighting should come off utility single phase.
2. All single phase tooling off the utility
3. Run the air compressor and air conditioning off the 54
4. Run the large shop equipment off the big unit.

You do NOT want to lose lighing in a machine shop. On second thought 3 phase lighting is good because you will have much lower problems with strobe effect than with single phase lighting. Lighting is pretty easy to balance out on three phase. One or two "emergency" single phase light and receptacle circuits should suffice if you have a generator trip out.

I do not think a lot of automation is what you really want to do. Manual load control will best serve your needs and allow best flexibility. You are a machinist - that is what you do best and make the most money doing.

Another option is to use rotary phase converters to "generate" 3 phase from single phase. This outfit may have stuff of interest to you
http://www.phoenixphaseconverters.com/category.php?id_category=61

You can also run 3 phase output VFD on single phase 220 input. Good option for motors say 10 to 15 HP and smaller.
Double check if it will work with CNC.
This may be worthy of consideration also.

Dan Bentler

 

[Lancie1]

An adjustable current monitoring relay in the generator output along with an adjustable time delay relay to restart the shedded load, the AC units in this case, would probably be adequate.

I do not think a lot of automation is what you really want to do. Manual load control will best serve your needs and allow best flexibility. You are a machinist - that is what you do best and make the most money doing.

I agree with these views. As PLC programmers, often all problems look as if the best solution involves the latest, fanciest, most advanced PLC. It is the view of the infantryman in the trench fighting a battle, and I understand that viewpoint. The best gun looks like the biggest, fastest-shooting bad dude with the largest available magazine.

But to the general fighting a war not just one battle, he can get a few big guns to scatter around among the troops, but he needs a bunch of smaller, less costly guns so that everyone has at least the minimum to fight the war. As company owner, you can't put all your assets into one small project by buying future capability that may never be used, and can't be paid for out of current earnings.

http://www.enercorp.com/curr/current_switch_225.htm

http://www.grainger.com/Grainger/ti...71&dojo.preventCache=1362137304921&sst=subset
A current transducer with current switch (see links) selected for the generator maximum operating current output, and a 15-minute time delay relay to avoid switching the load too fast, could do the job. For example, connect the CT switch output to a time delay relay that seals itself on for about 15 minutes, so the load can not come back on for some minimum time. That is a start, and a load contactor would probably be needed, along with a box to put it all in, some terminal blocks, wire, fuses, selector switches, and other materials.

 

[DEFM]

Bob is so right about gennys being temperamental things,the air comp that loads/unloads is key,it keeps unit under a load and when something else hits-no problem,as well as load dump stats,spot-on,from my limited experiences. I have found that they work most efficiently (Bob feel free to correct) at 30 -75% load.Running two gennys at once wouldn't be economical for me.The cnc's mostly have there own lights in them,and when power co fails we can still run,we're in a rural area and power can stay down a spell.I have a 110v outlet from genny and a male/male extension cord,trip breaker feeding shop from house,plug in "special cord" and back feed lights-I know super hillbilly.I'm tired of this and fix'en to put a 20-30kw single phase unit on line.Now,doesn't PLC stand for programmable lodgic control? do they use G code like my machines or maybe there like the latter that makes the G code work,I was told that there is a device to do what I need and plc was in the old guys statement,as well as scientific atlantic,found them got confussed,and now I'm here.BTW when I said magical I didn't mean to be sounding arrogant or any thing,I use tech I don't fully understand all the time -just seems like magic.Rob

 

[Lancie1]

Do they use G code like my machines or maybe there like the latter that makes the G code work,I was told that there is a device to do what I need and plc was in the old guys statement,as well as scientific atlantic,found them got confussed,and now I'm here.

Programmable Logic Controllers are not generic (not yet at least), and each brand has it own little progrqamming software that will allow the user to write a program for that brand only.

There is a steep learning curve: You have to learn about the various PLC types, brands, models, and catalog numbers within the units. Then you have to buy the PLC, the Input and Output modules, the cables, the programming software, get manuals, and all the other stuff needed. Now you are ready to start learning how to write the program. Many PLC software programs use ladder logic, which is a type of binary or Boolean logic. (You can find many ladder-logic PLC programs on this site). Ladder logic is a sligltly higher-level language than G code, in that symbols are used instead of the statement list assembler-type of code. Other PLCs (Siemens and Rockwell ControlLogix) mainly use function blocks or statement lists which would more closly resemble G code.

As with most tools, there is a wide range of capabilities in PLCs, from the very stripped-down, few-inputs, few-outputs, self-contained box units up to the large multi-function units. I don't think your application will require the larger more sophisticated type of PLC. In fact, right now I am thinking you will be best served by not using a PLC at all. It depends on how much time and effort that you want to devote to learning all about PLCs.

 

[DEFM]

Oh man,that sounds heavy,I might be better off putting a third genny on line, like a 146kw,for my heavy flow days.