At work we have a large Cummins get set we use to power a large portable screen plant. It originally cake from a coll get and was set up with a bunch of automatic controls which we had problems with. Cummins tech guy said the mother board was shot. We had them rework the generator to get rid of all the automatic stuff. When you flip the main now you have full power. Wired the gen interested he panel box of screen plant as usual. Went to do a trial run and try it out. All of the he conveyors on the plant get turned on in a certain order with he Shaker on the screen deck last. Voltage output was between 470 and 480. Perfect. When starting the conveyors the amp draw gauge would go up a little and then almost immediately show next to no draw. Everything still good. Last step is starting the shaker for the screen deck. This is where it goes not so good. Shaker has a soft start so it doesn't get full power right away. Hit the button for the shaker and amp draw gauge pegs at 250 amps. Volts still the same. This brings that big 6 cylinder cummins to it's knees almost stalling it out. This continues for about 20 seconds till the shaker is up to o speed. Once everything is running amp draw is around 65. This never happened before they worked on the gen. Did they do something wrong ? Will this hurt the electric motors on the screen ? Will this hurt the gen ?
- Thread starter 300jk
- Start date
Roger in Iowa
Well-known Member
Is the shaker the largest motor? If so, shouldn't it start first?? Can you start it first and try to see what happens.
It is a he largest motor. Problem is if you start the deck first it can flood all the belt under the screen if material is on the screen deck. If everything is empty you could start the deck first, but if not your just asking for problems. Last year that happened once. Had the under deck conveyor quit. Before I could shut everything off it packed the entire screen deck. 3 decks, three cavaties 2' tall, 8' wide and 20' long. 2 of us laying on our sides shoveling for over a day. Not fun !
How big of a unit is this, it sounds like a tiny baby one from your description, we have 16 that each run about 4,500 amps easily.
Do you trust the generator guru, or was it bubba?
Are the parameters in the softstart field programmable, if so increase your ramp time, a lot, everything i have on VFD?s or softstarters has a long enough ramp time to do some good, if you start things to fast it defeats the entire reason we use them.
Do you trust the generator guru, or was it bubba?
Are the parameters in the softstart field programmable, if so increase your ramp time, a lot, everything i have on VFD?s or softstarters has a long enough ramp time to do some good, if you start things to fast it defeats the entire reason we use them.
Steve@Advance
Well-known Member
Something doesn't add up, if the engine nearly stalls, the voltage should drop accordingly.
Makes me wonder if the volt meter is giving a true reading.
A couple things can make the motor hard to start. Mechanical binding or a heavy flywheel will cause over amping on start up.
Also a weak connection, as in a bad connection on one leg of the motor will cause high amp draw. The soft start, is it mechanical with a timer, or is it electronic?
Either way, be sure it is working properly, as in not hitting full voltage due to a bad timer, or if electronic, there is not enough time programed into the ramp up time. Also check the amp draw on each leg and the voltage across each leg. Amps should be close to equal and at or below FLA rating on the motor once up to speed. Voltages should be close to equal across each leg. Voltage should be the same into and out of the starter once up to speed. An imbalance in voltage ahead of the starter would indicate a problem with the gen set. An imbalance after the starter would indicate a problem with the starter. Balanced voltage and imbalanced amperage would indicate a problem with the motor. Be sure to check all connections, especially the final connections into the motor.
If everything electrical checks out, look at the engine performance.
Makes me wonder if the volt meter is giving a true reading.
A couple things can make the motor hard to start. Mechanical binding or a heavy flywheel will cause over amping on start up.
Also a weak connection, as in a bad connection on one leg of the motor will cause high amp draw. The soft start, is it mechanical with a timer, or is it electronic?
Either way, be sure it is working properly, as in not hitting full voltage due to a bad timer, or if electronic, there is not enough time programed into the ramp up time. Also check the amp draw on each leg and the voltage across each leg. Amps should be close to equal and at or below FLA rating on the motor once up to speed. Voltages should be close to equal across each leg. Voltage should be the same into and out of the starter once up to speed. An imbalance in voltage ahead of the starter would indicate a problem with the gen set. An imbalance after the starter would indicate a problem with the starter. Balanced voltage and imbalanced amperage would indicate a problem with the motor. Be sure to check all connections, especially the final connections into the motor.
If everything electrical checks out, look at the engine performance.
We checked for mechanical stuff first. I do understand about all three legs and the volt output. The old setup had gauges for each leg. New one does not. I am just a heavy equipment operator, but do get what your saying. We have no way, or the proper knowledge to see whats happening here. I am definitely not a generator tech. Since the unit has about an hour on it since they worked on it I guess they should come out and take a look ! Something isn't right !
Ramp.time seems the same. Panel box, and soft start for screen are separate from the power unit. Not Hing with the soft start or anything in the panel box have been touched. Sounds like you run some big stuff. We have draws like that in our quarry setup. This is just a portable unit. This gen unit went to cummins to.get switched over. Not shade tree mechanics.
Well if bubba gutted the controls that may be a clue, there is a lot more there than just starting it up, I would assume that since it came from a college it was a 480/277 wye, so depending on the actual capacity of it it may have had GFCI protection for equipment on the output, usually with a shunt trip breaker, you may want to get him back, or get a second opinion from someone that can see what?s going on, I?ve seen these bubba rigged up generators burn up thousands of dollars of motors and equipment over the years, hopefully your motor protection is correct.
Billy Shafer
Well-known Member
If it worked before they worked on it and it has problems now. Yes I would say they need to come back out and find their mistake. What is all this automatic stuff.If it is dragging it down that far something is wrong. I would start the largest load first.
Billy Shafer
Well-known Member
Why didn't they do a full load operations test before. They cleared it for operation.
Several of our customers are huge datacenters, I put the third 600 amp, 13,800 volt service in last spring at one, when we lose utility it gets loud and cloudy on a cold day, for those buildings I have a special phone number for Xcel, never get a recording, or automated system, last two new generators were big Detroit?s, one has so much crap we had to get 13,800 volt generators, no room for pipes at 480 volts.
Just be careful, a good fault will burn your face off, at best, short cuts when it comes to generators can cause problems, if all the controls were cut, if you get it running, watch it under ?load? before you get carried away, it may not take changes in load well.
Just be careful, a good fault will burn your face off, at best, short cuts when it comes to generators can cause problems, if all the controls were cut, if you get it running, watch it under ?load? before you get carried away, it may not take changes in load well.
A friend was remodeling a commercial space and needed some power. The meter had been pulled so he tried a hacksaw blade to bridge the meter socket.
Something was on and the blade exploded, burned his face mostly off. Somehow he drove himself to the hospital burn ward. Took months before it started to really heal....
It was set up as a backup at a college. Designed to come on when power went out. You could also go in the control screen and adjust the voltage on the legs. Has some type of mother board that went bad and that's why it worked erratically before we sent it in. I didn't send it out to be fixed, nor did I talk to anyone who worked in it. Just the guy who has to use the thing.
Destroked 450
Well-known Member
- Location
- Harned, Ky
You never said what size (KW) the gen set is nor what HP ratings the motors are.
Sounds like the shaker screen has the largest motor which should be started first.
No product should be left on the shaker screen when it's shut down, it requires more power to start a loaded shaker screen.
Who ever is leaving product on the screen when it's shut down should be reprimanded or fired.
250 amp draw on a soft start sounds like your starting a 50-75 motor depending on the inertia of the load and ramp time.
If the screen motor is smaller than 50 hp you have a problem with the motor, the screen is binding or your starting it loaded every time which is bad, bad, bad.
I'm not downing you or any one you work with but proper start up and shut down procedure's are important when working with limited power availability.
I worked and helped build a local saw mill, even though we operated off of utility power if proper start up and shut down procedure's weren't followed it could cost the mill owner thousands per month in increased utility bills.
On the last mill we build, with soft starts and frequency drives we could start nearly 1000 hp worth of motors ranging from 200hp down and only pull a max of 850 amps on the entire system during start up, so you can imagine the a$$ ripping the crew got when they managed to knock out the 2000 amp main switch gear and shut down the entire operation one day. All because they didn't follow procedure, the utility bill was an additional $2500 that month.
I totally agree with you about not leaving material on the
screen deck, and conveyors. When things go bad with conveyor
belts, drive belts or anything else conceivable with running a
crushing and screening operation sometimes it does happen.
Things for get shut down because of mechanical failures from
time to time with material still in the circuit until the
problem is fixed. Without explaining the whole setup sometimes
it is impossible to avoid. No material was in the screen, or
put through the screen yet. The issue I described was a
completely empty machine, and nothing was put through it. This
problem did not exist till the gen. was worked on. I let he
person in charge know what happened and that I thought it
wasn't right. Inam leaving it up to him now. If the owner wants
to ream someone it can be him not me. A different supervisor
was also present when we tried it out so I have my axx covered.
The guy in charge is not good with taking care for issues the
right way. Pretty much put a band-aid on it and run it till it
blows. I hate that !
screen deck, and conveyors. When things go bad with conveyor
belts, drive belts or anything else conceivable with running a
crushing and screening operation sometimes it does happen.
Things for get shut down because of mechanical failures from
time to time with material still in the circuit until the
problem is fixed. Without explaining the whole setup sometimes
it is impossible to avoid. No material was in the screen, or
put through the screen yet. The issue I described was a
completely empty machine, and nothing was put through it. This
problem did not exist till the gen. was worked on. I let he
person in charge know what happened and that I thought it
wasn't right. Inam leaving it up to him now. If the owner wants
to ream someone it can be him not me. A different supervisor
was also present when we tried it out so I have my axx covered.
The guy in charge is not good with taking care for issues the
right way. Pretty much put a band-aid on it and run it till it
blows. I hate that !
Billy Shafer
Well-known Member
The guy in charge. Needs to find another job.
Roger in Iowa
Well-known Member
I would think the machine should be shut down with everything empty. Then you could start it first.
Sounds like it needs some more electronics, so if something quits, it all quits. Otherwise you shovel....
Sounds like it needs some more electronics, so if something quits, it all quits. Otherwise you shovel....
Billy Shafer
Well-known Member
He says it worked before this repair. It should work now. I would be asking for some answers from the ones that did the work.
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