2200 HP soft start for fan ? crisis
2200 HP soft start for fan ? crisis
(OP)
We have several 2200 HP direct drive fans. They use a hydraulic coupling to let the motor go right to full speed, then bring the fan up to speed over a 3 minute period at ~ constant torque.
We have hit a major lack of spare parts problem with one of the couplings. The pressure is immense to get the fan back on line quickly in order to run ~ 6 months.
The Fan manufacturer says Direct coupling would require ~ 4000 HP motor.
ALL alternatives are being considered.
Short term generator and engine rental, giant soft start devices, 4000 HP used motors.
Dan T
We have hit a major lack of spare parts problem with one of the couplings. The pressure is immense to get the fan back on line quickly in order to run ~ 6 months.
The Fan manufacturer says Direct coupling would require ~ 4000 HP motor.
ALL alternatives are being considered.
Short term generator and engine rental, giant soft start devices, 4000 HP used motors.
Dan T





RE: 2200 HP soft start for fan ? crisis
There is probably a wider market and better rental prices for a genset than for the other options.
But, you may be able to rent a used motor short term from a used equipment dealer.
Direct connecting the motor to the genset before starting the generator and bringing the genset and motor up together to lessen starting stresses.
You may be able to bring the existing motor up to speed by direct connecting to a genset before starting the genset.
You may have to use manual field control or an external source of power to the AVR (Automatic Voltage Regulator).
You will be using the generator as a defacto VFD. The speed will determine the frequency and the UFRO feature of a modern AVR will maintain the V/H ratio.
I would locate a suitable used motor so that I had backup available but first rent a genset and try to start the existing motor. You may be back online quickly and at the best price.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
I'm a VFD guy myself, they can accelerate that motor in whatever time frame is necessary, so they can fully replace the fluid coupling. If possible, you could even have one VFD and some clever switchgear arrangements to "recycle" the VFD for each motor. But to be honest you will be hard pressed to get a VFD that quickly right now. Most manufacturers of MV VFDs are in full production just to keep up with demand, deliveries are typically longer than 6 months.
So I think waross' idea may be your best bet for success in that short of a time frame. I saw something similar done on a 6000HP 6600V motor once for an LNG pump system. Worked like a charm, although the generator rental technician on-hand for the startup was a little nervous (they hadn't fully disclosed how they were intending on using the gensets when they rented them).
RE: 2200 HP soft start for fan ? crisis
lol
Keith Cress
kcress - http://www.flaminsystems.com
RE: 2200 HP soft start for fan ? crisis
A. Motor type. Induction-squirrel cage, Induction-wound rotor, Synchronous,???
B. Motor voltage. 4160, 6600, 13,200,???
C. Is there any possibility of getting the motor and fan to turn slowly before energizing the motor?
D. Is this an ID and FD type of fan setup?
RE: 2200 HP soft start for fan ? crisis
What about an air clutch, similar to that used on a ball mill with Synchronous motor?
We need more info as Gianoli requests.
Good luck
Roy
RE: 2200 HP soft start for fan ? crisis
The originally closed damper is just cracked open to reduce very unpleasant starting flow characteristics.
6000 something volts.
not synchronous. Don't know rotor construction.
The motor mfr estimates the fan would have to be spun ~ 1/2 speed (~1200/2=600 rpm) to allow across-the-lines starting.
Fan owner is looking into air actuated/deactuated clutch.
RE: 2200 HP soft start for fan ? crisis
OK, here is a crazy idea, take it for what it is worth. I am sure it will draw some criticism.
· Motor voltage is likely 6600 volts. System voltage is likely 6900 volts.
· Motor is probably a 6-pole squirrel cage induction motor.
· Install solid coupling between motor and pump or lock up current defective coupling.
· Build small temporary hoarding around motor and try to insulate it with some construction blankets or temporary insulation.
· Get some air conditioners and try to get the motor as cold as you can prior to starting. Let it sit for a day when the temperature reaches it coldest point to ensure the stator winding and the rotor are as cold as possible
· Ask electrical folks if it is possible to raise the bus voltage on the segment of the electrical system feeding the 6600-volt motor. If the supply transformer has a tap changer they should be able to do this. If no tap changer is available they may have capacitor banks they can bring on line, which will raise the voltage temporarily. This is critical to the plan. The starting and running torque of an AC induction motor will vary as the square of the voltage. In general, a 10% voltage increase will get you a 21% torque increase and reduce the starting current 10%-12%. Try to get the bus voltage to about 7500 volts.
· If the motor has stator winding RTD's set up a way in which you can monitor them remotely during start up.
· Modify the protective relay settings to allow for a longer acceleration time.
· Start motor and fan while monitoring stator-winding temperatures. Abort start if stator temperatures become excessive.
I must qualify the above plan by stating that you will need to have a qualified electrical person on board to carry this out. Raising the bus voltage 10% is not a great idea in general however; if it can be raised temporarily and the electrical system is in good condition it should not cause any long-term damage. The motor stator winding can be monitored with RTD's, which I would think would be installed on most 6.6 kV motors. The motor rotor cannot. A plan like this could reduce the life of the motor. DO NOT monitor the stator winding temperatures from the front of the motor contactor or breaker door if that is the location of the protective relay. If you have to abort the start the motor contactor or breaker will have to interrupt starting current at a higher than normal voltage. No one should be any were near this unit during the starting period.
RE: 2200 HP soft start for fan ? crisis
You are wrong about drop in current with increase in voltage. We use soft starters, vfd's, star/delta starters etc. to reduce the suppy voltage and inrush current. Also, at the voltage levels you mention, the core saturation will drive the current way too high increasing both the core loss heat and the copper loss heat.
I would go by waross' suggestion of a cold start DG along with the motor. About 2 months back, I suggested this to a client of mine, who wanted to start 6.6 KV, 700 KW pump for a desalination plant for an initial start up, where the local utility did not extend the supply in time. With a hired 415 V, 1000 KVA DG and with a 6.6 KV/415 V, 1.5 MVA back-fed trafo, the initial trial run was successfully completed.
RE: 2200 HP soft start for fan ? crisis
You are right. My mistake.
In general, 10% increase in voltage also results in a 10% INCREASE in starting current. However, it does result in a 7% DECREASE in full load current and a 3C to 4C drop in temperature rise. This according the table I am looking at (Standard Handbook For Electrical Engineers, 12 Edition, Table 20-6.)
Thanks.
RE: 2200 HP soft start for fan ? crisis
RE: 2200 HP soft start for fan ? crisis
That decrease in running current with increased voltage would depend on the level of saturation per original design. These MV machines are custom-built and are generally running close to saturation at the nameplate voltage. Also, having a higher voltage during normal running (which will be a very hard thing to do in a network) raises the risk of insulation failure and definitely lowers its useful life.
ruggedscot
The genny-tranny combo was used to complete the entire pre-commissioning run of the pump since the site had only temporary construction power during that phase. As fas I know, that site is still awaiting the utility supply (which is government owned which explains the inefficiency and the lethargy)and the entire desal project is behind time.
Of course, in OP's case, he would have to change over to his regular supply once the motor gets to full speed (unless "the management" is willing to pony up for the continuous hiring of DG.
RE: 2200 HP soft start for fan ? crisis
Keith Cress
kcress - http://www.flaminsystems.com
RE: 2200 HP soft start for fan ? crisis
Let us know the final outcome. If you need to use two gen-sets, let us know. We can probably come up with a few tricks to simplify synchronization and control.
I would suggest starting with one set connected to the motor and accelerate as much as possible. Leave the controls set for 60Hz. The fuel limit should limit any over current to an acceptable level for the time of the start. The dead rack adjustment may be set back to limit the overload at full throttle if needed.
Now the second set should be running already. Set the speed down and sync it with the first set. Set the speed to 60 Hz.
When the fan is up to speed, sync with the utility power.
Last, set the frequency down on the gen-sets to shed most of the load and drop out the gen-set breakers.
This should avoid a lot of scampering and surprises trying to start two sets in sync and then trying to advance both throttles.
Any comments or further suggestions, itsmoked, skogs, jraef, edison, rugged?
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
I would skip the synchronization-with-the-utility part, which is going to be a b..ch. Take the motor up to full speed (you could even go a little beyond 60 Hz to get a running speed above the rated), trip the gen breaker. After a 2-3 second delay, switch in the regular utility supply on the fly since the motor speed would not have dropped significantly in 2-3 secs.
The 2-3 sec delay is to allow the flux (from gen supply) to die down.
RE: 2200 HP soft start for fan ? crisis
I would expect big sets that are well loaded to behave very well. It's the small lightly loaded sets that get flighty and can be hard to sync. A synchro-scope would be nice, but voltmeters or light bulbs may be used.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
I would love to see either method applied. I suspect edison's method as being a little more fumble proof.
Keith Cress
kcress - http://www.flaminsystems.com
RE: 2200 HP soft start for fan ? crisis
RE: 2200 HP soft start for fan ? crisis
Have you heard the saying?
"Close only counts in horseshoes and hand grenades!"
I would add synchronization.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
Pretty interesting when you try to work outside of the box and apply some devious thinking to a process....
RE: 2200 HP soft start for fan ? crisis
I don't generally make such sloppy sync's. I am embarrassed by anything past about 5 deg. It's hard to get much closer than 3 deg with small diesels and a manual 1000 amp breaker frame.
However, I was surprised to see just how sloppy a sync could be before it caused damage. These folk would be sync'ing in generators sometimes 10 or 12 or more times a day. Their operating procedure was such that they were sync'ing in generators when the load was dropping as well as when the load was increasing. (Add a 350 kW and then drop a 600 kW) They were doing it for 5 or more years before I found and corrected the issue.
The tip off was that whenever a unit was sync'ed, the syncroscope would jump to the 2 o-clock position when the breaker was closed.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
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If we learn from our mistakes I'm getting a great education!
RE: 2200 HP soft start for fan ? crisis
BTW, I'm one the plane back to that plant on Monday. They have a fuel efficient 1.2 mW set now and the days of sync'ing in 350 kW and 600 kW sets are behind us.
These trips are more an expense paid visit with old friends than a job. The island is hard to describe but I enjoy it.
The main community is on a coral reef with no roads or motor vehicles. Transportation is by sidewalk, push carts and boats.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: 2200 HP soft start for fan ? crisis
Keith Cress
kcress - http://www.flaminsystems.com
RE: 2200 HP soft start for fan ? crisis
After hurricane Mitch destroyed the entire distribution system, (only three poles left standing and they replaced them rather than trust them) the line contractor and his crew rebuilt the entire system by hand. The poles were set with pike poles, the wire was strung out by hand and the transformers were delivered as close as possible by boat and then dragged overland and hoisted by hand. It was something to see.
You can tell that I am thoroughly confused by Political Correctness in abbreviations. I was quite happy with KVA, KW, MW, MVA etc. (and of course milli-watts).
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
Talking about out of sync. Scate-boarders have their terminology. Like "a 180", "a 360" even "a 540".
I have not got any further than "a 180". That's as bad as bad can be. Read all about it in attached pdf.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 2200 HP soft start for fan ? crisis
I'm sorry, the wife had me out in the yard this AM with her Suburban and one of my old logging chains pulling up shrubs by the whole root system so I guess my mind was just wandering. But I have seen something like this done in the past, so I thought I'd throw it in. It might take a few trial runs to get it smoothe and to determine what ratio of speed/wraps would get you to 600 RPM, but what the heck.
rmw
PS: a neighbor asked me what kind of plants the were and I told him I was working from my neck down and except that I knew how to operate a logging chain I wouldn't be involved at all.
RE: 2200 HP soft start for fan ? crisis
At least at 180 degrees there would be little torque. Worst electrically but I vote for around 90 to 100 degrees as worst mechanically.
I would hire 6 or 8 of my friends from Eng-tips as consultants if I could.
But you probably don't want to see the crime scene photos of the body we found less than 100 yards from my hotel room on the way to the boat to the airport the last time I was here.
I guess I could best be described as a wandering adventurer who pays the bills with some knowledge and experience with electrical stuff.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
Can I be one of, them consultants ? I'll behave, I promise...
Seriously though, I like your wandering adventurer attitude.
RE: 2200 HP soft start for fan ? crisis
BTW, I have always been told that the 180 was as bad as bad could be. But, when I think about it, It is probably not so bad mechanically, force CW or CCW? There is a minimum at 180, as there is at 0. Currents and voltages high, but the breaker survived. Learned again.
Edison. Did you make that drama yourself? Have been looking at it for minutes. Like (some) projects, it starts optimistically and happily, gets difficult, then dangerous. If you stop there, you are wise. Being forced to continue (by your own ego or a boss) may take you where you don't want to be. Starting a 2200 HP fan could be such a project.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 2200 HP soft start for fan ? crisis
Something like a most memorable service call/ job/ adventure/ injury, location or memorable whatever.
I think that the participants are pub members. If anyone participating is not a Pub member please say so. We can stay here rather than cut you out.
Bill
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"Why not the best?"
Jimmy Carter
RE: 2200 HP soft start for fan ? crisis
I think that's a good idea Bill. Start a new Pub thread named "I'm in this for the fun - mostly"
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: 2200 HP soft start for fan ? crisis
RE: 2200 HP soft start for fan ? crisis