Fan application
Fan application
(OP)
Hello friends,
Company bought a used fan from an abandoned factory which i was assigned to install in our factory. The problem is when i start the fan(DOL starting) the motor protection trips. The motor is a 3 phs, 5.5 kW 50 Hz 230/380, delta/star, 20.8/11.6 Amps which i connected in star and set the OL to 12 Amps. When i measured the amps with a clamp-amp it showed 60 A and it droped slowly to 40, 30, 20 and finally to running current 10.2 A in about 4-7 sec, the problem is that the OL trips in 3-4 sec. My opinion is to install a soft starter but i am a bit undecided if it can supply the needed starting torque.
Waiting for your opinions.
Company bought a used fan from an abandoned factory which i was assigned to install in our factory. The problem is when i start the fan(DOL starting) the motor protection trips. The motor is a 3 phs, 5.5 kW 50 Hz 230/380, delta/star, 20.8/11.6 Amps which i connected in star and set the OL to 12 Amps. When i measured the amps with a clamp-amp it showed 60 A and it droped slowly to 40, 30, 20 and finally to running current 10.2 A in about 4-7 sec, the problem is that the OL trips in 3-4 sec. My opinion is to install a soft starter but i am a bit undecided if it can supply the needed starting torque.
Waiting for your opinions.





RE: Fan application
We have many of these that we DOL/start in delta and leave in delta.
I would not try DOL start in star and leave it in star... if that's what you're doing. The motor would have reduced capability.
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(2B)+(2B)' ?
RE: Fan application
Star-delta would not be a good choice in this application for the reason you mentioned.
Rafiq Bulsara
http://www.srengineersct.com
RE: Fan application
From the ratings, 50Hz, 230/380V, this sounds like an IEC motor. It is common practice across the pond to change connections between star and delta to change the voltage rating of motors rather than for wye/delta starting. The motor starts and runs on delta on 230V systems and starts and runs on star on 380V systems.
Bill
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"Why not the best?"
Jimmy Carter
RE: Fan application
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(2B)+(2B)' ?
RE: Fan application
RE: Fan application
RE: Fan application
RE: Fan application
Opinions?
RE: Fan application
Plus that is not the real issue. Set the O/L correctly, this is not complicated.
Rafiq Bulsara
http://www.srengineersct.com
RE: Fan application
It looks like since it is a fan and running at STAR,the motor takes a long accelerating time.
1)Are you using an O/L relay with class 10 charateristics?Beacuse it is a fan and not like a cetrifugal pump,you may have to use Class 20,which will give sometime for the starting current to die down without tripping.
2)Also check your installation to see why it is taking such a long acc time.One reason may be the air discharge line is too long to handle by the fan.
3)No need to buy a soft starter.Use a star-delta starter and run at delta with class 20 O/L relay.
RE: Fan application
If your line to line voltage is 380 volts then you can not start this motor with star-delta combination, because the motor may not be connected at all to 380 V voltage in the delta connection.
Zlatkodo
RE: Fan application
I apologize that I got this thread off on wrong track talking about star/delta start.
It is not a motor designed for connection to 380 with star/delta start (as I originally thought)
It is a dual voltage motor – 230 connection in delta, 380 connection in star.... as you said.
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(2B)+(2B)' ?
RE: Fan application
waross what do you mean by "230V systems and 380V systems".
RE: Fan application
If that doesn't work change the overloads relay to a class 20 as Kiribanda suggests.
Actually, a long discharge pipe may drop the current on that type of fan. The fan may perform better when the discharge piping is installed.
If your line to line voltage is 230 Volts or close to it, you have a 230 Volt system.
If your line to line voltage is 380 Volts or close to it, you have a 380 Volt system.
Bill
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"Why not the best?"
Jimmy Carter
RE: Fan application
It sounds as though your fan is installed in your system and it operates at close to full load when is in steady state operation. If you have a long ducting system the flow through the fan will be higher than normal while the ducts come up to full pressure. You might want to see if you need this full flow all the time. If you do, you could use a damper to restrict flow until the blower comes up to speed.
RE: Fan application
That IS the problem. Not only it is low, the relay may be of wrong thermal class. Also see what Kiribanda said Or get an help of an experienced "electrician".
Rafiq Bulsara
http://www.srengineersct.com
RE: Fan application
RE: Fan application
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Fan application
RE: Fan application
As for overload relay you may have Class 10 relay and need to be changed to class 20, which has greater time delay (20 sec at 600X vs. 10sec) at given current. See this link http://sea.siemens.com/step/pdfs/cc_2.pdf
What you are observing is very normal. After all starting a 5.5 kW fan on DOL should not be a challenge.
Rafiq Bulsara
http://www.srengineersct.com
RE: Fan application
Rafiq Bulsara
http://www.srengineersct.com
RE: Fan application
Radial flow fans draw less torque with damper closed
Axial flow fans draw less torque with damper wide open
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RE: Fan application
Thanks rbulsara.
RE: Fan application
You are welcome. Hope that it works out to your satisfaction. Do let us know as to how it turns out. We all learn from our experience.
Just another note, make sure that the motor selected is of right type (thermally) and/or limit number of successive starts and starts per hour to limit the heat build up. Or you can easily damage the motor.
Rafiq Bulsara
http://www.srengineersct.com
RE: Fan application
If you want a class 20 then ensure the motor safe stalled is >20 seconds before installing it.
A soft-starter will provide a less dramatic start but it will not lower the amount of motor heating. It will likely include it's own overload that actually works as rated though.
RE: Fan application