How To Reduce Starting Current Required By Soft Starter To Start A 220 Hp Motor To Rotate A 12 Ton Flywheel
Posted 04 November 2006 - 12:44 PM
HOW CAN I REDUCE THE INITIAL CURRENT REQUIRED ?
CAN SOME ONE SUGGEST ME A WAY ?
IS THEIR A SOFT STARTER THAT WORKS ON STAR DELTA PRINCIPAL ?
IS THEIR A SOFT STARTER WITH 6 WIRE OUT PUT ?
Posted 04 November 2006 - 01:16 PM
This will allow you to accelerate the motor (and flywheel) either under current limit control or with an acceleration ramp time set long enough to keep the current from exceeding 100 % motor FLA.
Have done this in many such applications. Works Good!
With Genset though, you need to also be concerned about Harmonics on the mains from the Genset. The harmonic distortion has been known to disrupt the voltage regulator circuitry of the Genset. Some means of Harmonic mitigation will be required to prevent this from being a problem. This can be in the form of 5% line reactors or 5-7 harmonic trap filters. A harmonic analysis will identify the correct solution.
Posted 04 November 2006 - 05:35 PM
One experiment you could easily do with what you have now is to set your current limit lower to see if it is possible. If the motor stalls or overloads, don't waste any more time on that avenue. If the SOFT STARTER trips out on Over Temperature but you determined that the motor was still accelerating when it did, then there is a remote possibility that you can do it with lower current and a better rated soft starter. To be honest though, that is a very remote possibility.
If that doesn't work, then you have fewer choices available. One is a VFD as JOmega mentioned. Another popular choice with large flywheel loads is a magnetic drive system, essentially a magnetic clutch. The only other one I know of would be to use a Pony Motor; a smaller motor used to partially accelerate the flywheel, then finish it with the soft starter. That is still a risk however. The VFD or Mag-Drive would be the lowest risk of failure for you.
By the way, typing in all capital letters makes your posting very difficult to read. Humans read not only by looking at letters, but also by looking at the shapes of words. When you use all caps, the shapes blend into one another and force the readers brain to read each letter to make words, which slows down the reading process and subliminally frustrates the reader. Most people who use forums and email consider all caps to be a form of YELLING!
Posted 04 November 2006 - 07:17 PM
Posted 04 November 2006 - 10:48 PM
One other important consideration ...... How do you plan on stopping the motor with the flywheel load ?
Could you share any of the application mechanical detail with us ?
Here's what would be important to know:
- Motor kW
- Motor Frame Size
- Rated Motor RPM
- Inertia of Flywheel
- Min. Time to Accel Flywheel _____ seconds to what ______ RPM
- Time for Deceleration of Flywheel ______ seconds to what ______ RPM (if other than zero)
If you decide to pursue the VFD solution, it will not be inexpensive, particularly if you also have to add a dynamic or regenerative braking control and harmonic filtering to it. I would offer that had the company spent a few more $$ to purchase a Genset with a power rating that would support DOL or Soft-Start acceleration of the motor/flywheel , it would have cost them less $$$ overall.
Seems there is an 'old' saying: $0.01 wise ; Kg foolish ......
But, from such experiences, hopefully, comes future wisdom.
Posted 07 November 2006 - 11:54 AM
First of all let me thank you all to have shown interest to my problem and your valuable suggestions.
We do not intend to have a 300 kva genset against a 550 kva genset because of the purchase cost of the same, my running load requirenment can be fulfilled by a 300 kva genset. By taking 550 kva genset the running cost to the customer is more therefore we want to use 300 kva genset.
Motor KW = 160
Motor rated RPM = 750
Rotar RPM = 560 (reduction by pully)
Estimated time to reach full RPM = 40 secs
My equipment is a shredder to shredder ferrous scrap, the inside rotar is approx 12 tons.
i have used hydraulic cylinders to lift the rotar during maintainence. i can use this hydraulic power to give my rotar the initial start through a clutch system and the rotar can be brought to 100 RPM with the hydraulic power, now on reaching 100 rpm if i start the motor through the soft starter, will it work with the limited current available (ie. on 300 kva genset).
Posted 07 November 2006 - 03:55 PM
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