3/13/2012 6:52 AM | |
Posts: 165 Rating:
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hello experts Is it possible to get a "rated torque @ zero speed" in Induction motor ? Thanks Regards Mothilal |
3/14/2012 5:04 AM | |
Joined: 4/23/2010 Last visit: 11/23/2024 Posts: 8092 Rating:
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No. In industion motor the rated torque is available at rated nameplate speed with rated poweronly. |
3/14/2012 5:18 AM | |
Posts: 165 Rating:
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Hi PISCEAN Thanks for your reply. Hmmm .. What about servo motor? can we get the servo motor rated torque at any desired speed ? Regards Mothilal |
3/14/2012 6:49 AM | |
Joined: 4/23/2010 Last visit: 11/23/2024 Posts: 8092 Rating:
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Hi Mothilal, Servo motor generally two torque ratings are mentioned One at zero speed i.e. static torque (Mo)& the other available during entier speed range of motor upto its rated speed. (Mn) Depending upon motor type number & comparing its speed torque motor user can be able to read torque available at particular speed. Please find attached here with sheet of speed torque graph of Siemens make servo motor, which you can refer. Hope this help you. DEEP. AttachmentSpeed Torque graph.pdf (981 Downloads) |
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3/16/2012 10:18 AM | |
Posts: 165 Rating:
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hi deep At first I have asked one question about "induction motor rated torque at zero speed". By keeping the v/f ratio constant, why cant we get the rated torque at zero speed(aprroximately at low frequency) In VFD drives, the operating flux density of the machine is kept constant throughout the entire speed range(because v/f= constant). So will the motor produce rated torque (according to the name plate detail) during entire speed range? from one article about VFD: " During acceleration, the inverter applies different frequencies to the motor. It also changes the voltage but in direct proportion to the frequency. This is know as constant volts per hertz and provides constant torque while the motor accelerates. The “constant torque” represents the full load or rated torque of the motor. This “constant torque” line is actually the full load point on a locus of curves representing the speed torque curves of the motor from 0 to full speed. The inverter produces rated motor torque from 0 to rated speed. It will produce full load torque while drawing much less than full load current from the power line during starting. This is due to the fact that the motor is effectively always running at speed for the applied frequency." |
Last edited by: Mothilal at: 3/16/2012 10:19 AM |
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3/16/2012 3:00 PM | |
Joined: 4/23/2010 Last visit: 11/23/2024 Posts: 8092 Rating:
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Hello Mothilal, It is mainly because of construction of motor. In case of squirrel cage induction motor, it is not designed or manufactured for rated torque at zero speed. In squirrel cage induction motor slip factor plays a important role. Slip RPM varies in between 60-70 RPM ( for 4 pole motor & its general). Also the rotor response time is also low. To have a rated torque at zero speed, motor rotor response timemust bevery fast & motor designe is very special. (Rotor with permant magnet, rotor positioning mesuring system, & ofcourse handshaking operationby drive & special stator construnction. etc) So mainly it is motor who gives you rated torque at zero speed with intelligiant drive & not only VFD or AC drive which gives you rated torque at zero speed. Hope I am able to explain it a bit. Regards, DEEP. |
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4/18/2012 8:41 AM | |
Joined: 7/8/2009 Last visit: 8/5/2024 Posts: 1976 Rating:
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With AC drives, I think its possible Have a look at attachment This will also helpful for yout another Query Regards, Devesh Vithani AttachmentAC Motors.pdf (934 Downloads) |
I dont Like people driving Fast, thats the reason I overtake them ;) |
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