soft starter 5

[Safi A Jasem]

Dear
I used ABB soft starter for start motors
But I want to change 200KW 1000 rpm slip ring motor with oil starter to 200 KW 1000 rpm squeal cage motor with soft starter ,
but my challenge is distance between motor and circuit breaker is over 300mt ,
the old oil starter near install near motor now I want to install soft starter near circuit breaker .
Please I want your advice

 

[jraef]

Nothing to worry about with regard to distance, other than the usual issues of conductor sizing for voltage drop, etc. you might be confusing soft starters with VFDs, which do have issues with distance from the drive to motor. Those issues do not apply to soft starters, it's a totally different technology.

My real concern however may be in that the slip ring motor, with the proper resistance applied to the rotor, may be capable of more accelerating torque than the soft starter on a squirrel cage motor will given the same amount of current. In other words, you may find yourself in a current limit situation where the motor fails to accelerate, or your starting current may be more than your system can deliver. You may want to spend some more time evaluating this in detail before spending money. Sometimes, if the motor is still in good shape, it is better to leave it in place, find an optimum rotor resistance level to apply during acceleration with the soft starter, then short out the resistor after the soft starter finishes ramping.



"Will work for (the memory of) salami"

 

[Safi A Jasem]

Dear Jraef.
Thank you for your answer
According to the slip ring motor I will change this motor to squeal cage motor , because I have many problem with carbon brushes, slip ring and oil starter ,

 

[jraef]

So to be safe, you must evaluate the mechanical speed and torque needs of the machine, then select the correct size of 6 pole Squirrel (not squeal) Cage Induction Motor to match what the slip ring motor was doing for you. After you are sure that you have the correct amount of torque, you will know the proper kW size and only THEN should you embark on selecting a soft starter.

Or if you have already determined that your 200kW motor is sufficient and just wanted the information on distance etc., I already answered that for you and you are ready to go.

Good luck.

"Will work for (the memory of) salami"

 

[Safi A Jasem]

Dear
Thank you

the original motor is 190 KW slip ring for belt conveyor I will change it with 200KW Squirrel cage motor with same speed.
best regards

 

[LionelHutz]

That doesn't sound like a very good plan if you expect the new motor to start with a loaded conveyor. You'd better make sure the power source and soft-starter are both capable of supplying rated voltage and current to that new motor because you may need all the torque it is capable of. You'll be changing your conveyer system from requiring around 2X to 2.5X motor FLA to possibly requiring >6X motor FLA.

 

[Marke]

LPS to Jraef and LionelHutz. They have given very good advice.
The problem is that a loaded materials belt conveyor can require as much as 180% torque to start it loaded.
The Slip Ring motoor is able, with a good secondary resistance starter, to provide 200% torque at not much more that 200% current. A squirrel cage induction motor and soft starter can not achieve the same results. Using a soft starter on an induction motor, will reduce the start current from LRI (Locked Rotor Current - commonly in the order of 800% for modern HF motors) and it will reduce the start torque by the square of the voltage reduction.
If we assume a LRI of say 800% and a LRT or 240%, then we need to reduce the torque no more than 180/240 (= 3/4) so the current reduction would be square root (3/4) times 800 = 692% start current which is a start current more than three times the start current with the slipring motor. The actual figures will depend on the motor chosen, but if you just put a standard rating high efficiency motor and a standard rated soft starter to replace the slip ring con figuration, it could end up in tears. - you may need a big net to catch the smoke.

Best regards,
Mark.

Mark Empson
Advanced Motor Control Ltd

 

[waross]

Has any one been using RTV silicon in the vicinity of the slip rings. Most slip ring brushes have very long lives, but RTV silicon curing in the vicinity of the brushes is a known brush killer.
If you solve the brush problem you may replace the oil starter with a suitable contactor.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

We still supply soft-starter and resistor combinations for new conveyer applications using wound-rotor motors. For one company, the manufacturer and client together determined it's the simplest and most reliable way to start the big loaded conveyers vs other methods like a vacuum breaker and multi-step resistor starter or a squirrel cage motor and a VFD.

If you are having issues with abnormal brush wear then you need to find a better expert to figure out why. They should be quite reliable if you have a weekly maintenance schedule for dust cleaning and brush wear checks.

 

[proelect8717]

Dear Safiabd,

All the advices given by expert electrical engineers are very valuable and practical. If is it possible for you to share the data sheets and curves of existing motor, resistors, and all systems also with which you are planning to buy (softstarter and squirel cage motor) then it will be very helpful for all to evaluate and give more specific advice on your case.

Thanks.

 

[Safi A Jasem]

Dear All
Thank you for ALL.
I will collect all date sheet of belt conveyor and .send it ASAP
In the same case I have centrifugal fan with slip ring motor 190KW with oil starter , I plan to change it to soft staretr