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Starting Fan Motor In Star ? |
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 Sep 30 2008, 09:38 PM
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#1
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Junior Member  Group: Members Posts: 4 Joined: 30-September 08 Member No.: 4,853  |
having discussion regarding motor fan motor in work.
can fan motor be wired in star, if i remember you can only wire them in delta. because wiring in star would burn out the motor after a while. i know this question may sound stupid ,but we don't work mainly on motor. could somebody explain. and educate us. thanks timetunnel |
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Oct 1 2008, 07:04 PM
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#2
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 Posting Freak Group: Moderator Posts: 669 Joined: 22-February 03 From: USA, California Member No.: 285 |
If you wire a motor in Star when it was designed to be wired in Delta, the motor kW output will be reduced to 58% of what the motor is rated for. So for example, a 10kW motor will now only be capable of 5.8kW of load. If your load has been reduced to only needing 5.8kW, then no problem.
A fan works on air flow as far as loading goes. So if you have dampers that can reduce the total air flow enough, then it will work. But roughly, the power required to operate a fan is related to the cube of the airflow, so to reduce the power by 58%, you would need to reduce the flow to a value that is the cube root of .58, or 84%. So at 84% air flow, you can operate a fan in Star. Any more than that and the motor will overload. -------------------- "He's not dead, he's just pinin' for the fjords!"
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Oct 1 2008, 10:19 PM
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#3
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Junior Member Group: Members Posts: 4 Joined: 30-September 08 Member No.: 4,853 |
QUOTE (jraef @ Oct 1 2008, 08:04 PM)  If you wire a motor in Star when it was designed to be wired in Delta, the motor kW output will be reduced to 58% of what the motor is rated for. So for example, a 10kW motor will now only be capable of 5.8kW of load. If your load has been reduced to only needing 5.8kW, then no problem. A fan works on air flow as far as loading goes. So if you have dampers that can reduce the total air flow enough, then it will work. But roughly, the power required to operate a fan is related to the cube of the airflow, so to reduce the power by 58%, you would need to reduce the flow to a value that is the cube root of .58, or 84%. So at 84% air flow, you can operate a fan in Star. Any more than that and the motor will overload. thanks for your reply, very interesting to know. as i have never come across a motor wired in star, unless it was used in conjuction with delta [star-delta]. would i be correct in saying it would be very rear for a motor to be wired in star, unless it was a star -delta, if so, could you give me some examples of motors that woud use star. thank you timetunnel |
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 Oct 2 2008, 10:27 AM
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#4
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Member Group: Full Member Posts: 187 Joined: 16-August 05 Member No.: 1,186 |
Dear jraef,
I beg to differ. The power would be reduced by 3, from P=2*pie*N*T. Regards. Bob |
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Oct 2 2008, 05:53 PM
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#5
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Posting Freak Group: Moderator Posts: 2,383 Joined: 24-April 02 From: Christchurch, New Zealand Member No.: 1 |
Yes, I agree.
The voltage is reduced to 58%, but the power is reduced to 58% squared so is one third. There certainly are motors designed to be used at their rated voltage in a star connection. This is very common in some parts of the world and some voltages. Motors designed for the European market have traditionally been designed for star delta starting and so have all six tails brought out and are designed to operate in delta at the rated voltage. Best regards, Mark. -------------------- Mark Empson administrator
Skype Contact = markempson | phone +64 274 363 067 LMPForum | LMP Tech Warehouse | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | LMP Software | Mark Empson Website |
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Oct 3 2008, 04:05 PM
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#6
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Junior Member Group: Members Posts: 4 Joined: 30-September 08 Member No.: 4,853 |
QUOTE (marke @ Oct 2 2008, 06:53 PM) Yes, I agree. The voltage is reduced to 58%, but the power is reduced to 58% squared so is one third. There certainly are motors designed to be used at their rated voltage in a star connection. This is very common in some parts of the world and some voltages. Motors designed for the European market have traditionally been designed for star delta starting and so have all six tails brought out and are designed to operate in delta at the rated voltage. Best regards, Mark. would a star motor have to be rated more ? as in double, to have the same output as a delta motor. so why would you use a star rated motor over a delta motor. |
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Oct 3 2008, 07:41 PM
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#7
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Posting Freak Group: Moderator Posts: 2,383 Joined: 24-April 02 From: Christchurch, New Zealand Member No.: 1 |
Hello timetunnel
A motor can be wound for star connection at rated voltage, or for delta connection at rated voltage. There is essentially no difference between them provided they are run at their rated voltage. If you have a motor designed to be connected in star at your supply voltage, use it in star. If you reconnect that motor in delta at the same voltage, you increase the voltage across each winding by root 3 and you thereby increase the flux in the iron and will damage the motor. If you take a motor that is designed to be connected in delta at you supply voltage and connect that motor in star, you reduce the voltage across the windings to 58% and thereby reduce the flux in the iron. This reduces the torque capacity and thus the power capacity of that motor to one third. A motor that is wound for delta can be rewound for star at the same voltage by reducing the number of turns on each winding. Best regards, Mark. -------------------- Mark Empson administrator
Skype Contact = markempson | phone +64 274 363 067 LMPForum | LMP Tech Warehouse | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | LMP Software | Mark Empson Website |
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Oct 4 2008, 08:28 AM
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#8
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Junior Member Group: Members Posts: 4 Joined: 30-September 08 Member No.: 4,853 |
QUOTE (marke @ Oct 3 2008, 08:41 PM) Hello timetunnel A motor can be wound for star connection at rated voltage, or for delta connection at rated voltage. There is essentially no difference between them provided they are run at their rated voltage. If you have a motor designed to be connected in star at your supply voltage, use it in star. If you reconnect that motor in delta at the same voltage, you increase the voltage across each winding by root 3 and you thereby increase the flux in the iron and will damage the motor. If you take a motor that is designed to be connected in delta at you supply voltage and connect that motor in star, you reduce the voltage across the windings to 58% and thereby reduce the flux in the iron. This reduces the torque capacity and thus the power capacity of that motor to one third. A motor that is wound for delta can be rewound for star at the same voltage by reducing the number of turns on each winding. Best regards, Mark. i would like to thank everybody for there help in giving me there information on the understanding of both star and delta. regards timetunnel |
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