3 phase line .....

[Lancie1]

On the other hand, there are the programmable "smart relays" that Okie hates so much, that you could learn to program in 30 minutes, with no software or cables to buy, and probably a smart relay would do your job (barely).

As I see it, the basic function is:

"If generator current >= XXX, then switch Contactor off to prevent Load A from starting or running for X minutes".

That basic function can be done with a current transducer switch, a smart relay, a PC computer with programmable I/O module, a PLC, or a PLC with operator graphic panel. Each of these levels adds capabilities but also increases the cost and required knowledge level.

On the other hand, if the control device needs to consider several load possibilities, and pick the best one for any given set of input parameters, maybe by inhibiting several loads instead of only one, then a PLC is a good solution.

 

[Lancie1]

Question: If you had a PLC program that could read your generator current, and block a certain load or a group of loads from starting, what would you do if you needed to run the load(s) that was being blocked?

Would you then have to somehow bypass the PLC and run the blocked machine anyway? If so, then it seems that you really don't need a device to block a load, but a device to warn you of a pending generator overload, and present you with a list all the possible load combinations that COULD run, and so give you a way to prevent the overload, but leaving it up to you as to which machines to actually turn off.

 

[Temper]

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 no expert (zero generator experience) but be careful about back feeding the utility. You don't want to kill a linesman who's fixing the line down the road.

 

[Lancie1]

I'm no expert (zero generator experience) but be careful about back feeding the utility. You don't want to kill a linesman who's fixing the line down the road.

Killing a lineman is not likely, but damaging your generator is possible if you put it on the utility line. I used a backup generator with the same male-to-male plug for 30 years, always turning off the main breaker before plugging in the generator. Now I have a Reliance Generator-Ready 200 Amp circuit breaker panel in my house, which has a built-in interlock device to prevent having the main and generator breaker on at the same time.

That reminded me to update my house circuit breaker panel schedule. Most panels do not have a circuit directory that allows identifying every device connected to the panel. Here is an Excel spreadsheet that you can fill in with your circuits, then print out on one sheet. Get a plastic sleeve and tape it to the inside of your panel door, then slide the print-out into the sleeve. Update as needed.

 

[leitmotif]

Trying to put my thoughts in an all inclusive and short statement.

PLC and other auto systems (including old style relay logic with row n row of relays) is fantastic where the process is well understood and is always done the same way every time.

You are a machine shop with one of two scenarios
You have a huge contract and the process is the same day in day out for months on end. PLC may have a chance to handle this assuming a few days spent on design and setup. Couple more for programming. Week for you to gain enough about new to you PLC to make it handle the basics. Two weeks to fix errors and what you forgot todo or did not think of.

Case TWO You are a job shop and every day is different. Because of all the permutations of the steps in the process it is near impossible to predict what sequence of machinery you will need on Mar 22.

I recommend
1. very good line volt and ammeters for each phase on each alternator. Ideally these would be in machine shop to avoid traipsing back and forth to generator room.
2. A green (80% load or less) orange (80 to 90% load) and red light (95 plus) AND alarm to let you know alternator loading in the machine shop. This way you can look up from lathe or whatever machine and see how Rob Power and Light is doing.
3. I would also have temp monitoring of units in machine shop and an over heat alarm set such that you have time to unload and take action to cool engine.

Dan Bentler

 

[DEFM]

Ok guys I think I made progress today,I called Automation Direct and they were very helpful,I talked to a tech and once we bridged plc speek to hillbilly we made headway.they got a device-can;t remember what he called it-that you run your main lines into then on to your panel,this reads volts, amps draw,and other stuff,then it reports info to a plc in it's language.It only runs about 127$.Now the part where I got dizzy,programing the plc.As best I can figure it's like the ladder for my type machines.I don't play with that stuff,it cost too much to have someone who knows what there doing fix what I messed up so they can fix what was wrong to begin with.Realising I was over my head the tech gave me a coulple of plc enginneers that I could call,so I did,Florida automation machines,we will see how this goes.Leitmotif,I'm case 2,sometimes when I think I know what I'm doing in the morning it changes by lunch.Temper never killed no one,always trip main first,so if power comes on it stops there and mine also can't back feed power co lines.Lancie only want to "block" motor for a second and only IF the amp draw is high.The blocked motor is the ac and if it waits a few seconds to start there's no harm.All this stuff happens so fast,once a motor stars the large amp draw falls off,as I'm sure y'all know.I sat still today and listened to the genny as all was running and it's amasing how fast the genny reacts to all the draws and dumps.If you guys want I'll let you know what this fella comes up with,I kinda hope you do,cause he could put some blinking lights on a box of s#&* and I wouldn't know the differance,Rob

 

[leitmotif]

We do not have many people who come back and report the results of their efforts. We appreciate when someone does come back and let us know how things worked out.

Dan Bentler

 

[DEFM]

thats great,I'll make sure to write down what is sugested so I can run it by you guys before I agree to any thing.Again,I can't thank you guys enough,Rob

 

[Lancie1]

They got a device-can;t remember what he called it-that you run your main lines into then on to your panel, this reads volts, amps draw, and other stuff, then it reports info to a plc in it's language.

It is a Power Monitor (previously known as a Wattmeter in another era), reporting to the PLC through a communications network, Ethernet or Modbus comms probably). To know if the generator is overloaded normally would only require a current reading, but if you can get all power parameters for $127, then it is a bargain. A power monitor could help if there is an unbalanced phase condition later.

Realising I was over my head the tech gave me a coulple of plc enginneers that I could call, so I did, Florida Automation Machines, we will see how this goes.

I think that was a smart move, it could save you a lot of time and headaches. Use your time to do the things you know that will improve you business, and farm out the details to experts in each area.

 

[leitmotif]

Another thing to think about. Starting a load on a generator will cause it to slow somewhat until governor recovers the speed. This slowing reduces frequency let us say 2 or 3 Hz if a good governer.

Now on a 3600 RPM motor 1 Hz = 60 RPM so if you decrease line freq by 2 Hz your motor is slowing by 120 RPM then speeds back up by 120 RPM. This causes your gearbox to do slow (braking the load) and then speed back up. Can be and is hard on gearboxes. On a normal lathe or mill this may not be a big thing but CNC runs a lot faster in many cases.
May have implications on cutter and on precision of part produced.

I would keep cycling loads on one generator and use other for loads requiring constant RPM

Dan Bentler

 

[DEFM]

Lancie,thanks for the support on my decision to "seek profesinal counsiltion".I pretty much built my building learning as I went,when it came to dry wall inside the shop I did the first wall (how hard could dry walling be?).Well I learned a valuable lesson there,and thank GOD,I didn't let pride get in the way,now the shop looks good and at half the cost in materials.I can do wiring, put up conduit and such,but with this I see a major *** whoopin.Leitmotif,I've watched the display on the genny,and your right about the hrz.but its only.2-1.3 max.The gennys have a control-might be a plc for all I know-that regulates and moniters many things ,it is made by Deep Sea Electronics,come to think it's got parameters.Got the first step done today(with wife's help),made a list of all 3p equipment and did the best I could to list amp draw of each.Here it is what do you think?

 

[OkiePC]

At some point a wiring diagram is going to be very helpful.

The PLC needs to know the impact of each load when it is requested, and have a means to prevent it starting (optionally shut it down depending on how you wire the interposing relay contacts).

 

[shooter]

your action of starting the compressor is very good, it will be a nice load, and when anything is started the motor will work as generator for short while, thuss keeping the generator within limits.
try to have a big motor (even unloaded) running before starting big cnc
have the lights switched in three phases (just three switches going to every phase one. or 5 lamps each phase. (they are known to mess up the load control)
it is unadvicable to have the gen coupled on the landline,
use a take over switch to have the landline take over some parts.
the amp meter will go up and down that is no problem witin 10 % of full load more important is the controller on the genarator is that nioce and steady?
the cnc machines all have their own stabilizers and supplies so do not worry about them.

 

[DEFM]

Shooter,thanks for the advice,Okie,wiring diagram?.Do you mean a deisciption of how the wires are in real life?I think the air comp acts like the big motor,when the comp unloads,the motor still runs.True about the land line,the genny is isolated from it.Take over switch? the land line is single phase and the genny is 3 phase.

 

[Lancie1]

Take over switch? The land line is single phase and the genny is 3 phase.

It is still possible with a phase converter, but may not be practical if the land line has limited capacity, 100 Amps or less. Above that, maybe. A 200 amp 240 volt line can supply about 48 KVA 1-phase, or about 22 KW when converted to 3-phase (approximately 50% of the 1-phase KVA). Power can be converted electronically with a 1-phase IN to 3-phase OUT Variable Frequency Motor Drive (VFD), or a rotary phase converter like this Phoenix unit:

http://www.phoenixphaseconverters.com/product.php?id_product=12