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#61
06-30-2012, 10:14 AM
 kishor5466 Member Join Date: May 2012 Posts: 43
Re: DC Electric Motor

Quote:
 Originally Posted by major No. You had better learn to read a graph. You could ask your instructor or do a search on this forum and find where I have explained how to read motor performance characteristic curves.
this must be correct ,,,,,,,
"I" at 6000 is 500A....
according to the formula given for "U" and the value of current, the motor will provide 206kw of energy right???
#62
06-30-2012, 10:22 AM
 kishor5466 Member Join Date: May 2012 Posts: 43
Re: Power rating of a motor

Quote:
 Originally Posted by major if the 32kW rating on the motor is peak, then it will not tolerate such a high load. If the motor can tolerate such an overload, it would not be for long, or frequently.
okay tell me if it can tolerate that much of overload for less than 8 seconds???
And in general what is the fraction of the overload a motor will be able to take if it's overloaded to that extent under 8 seconds( say for safety 10 seconds)??
#63
06-30-2012, 10:37 AM
 major Senior Member Join Date: Apr 2008 Location: Ohio, USA Posts: 5,185
Re: Power rating of a motor

Quote:
 Originally Posted by kishor5466 okay tell me if it can tolerate that much of overload for less than 8 seconds??? And in general what is the fraction of the overload a motor will be able to take if it's overloaded to that extent under 8 seconds( say for safety 10 seconds)??
Inquire of the motor supplier or test it yourself. Rarely if ever is an 8 or 10 second duty rating published for a motor. Again, what does your professor tell you?
#64
06-30-2012, 10:44 AM
 major Senior Member Join Date: Apr 2008 Location: Ohio, USA Posts: 5,185
Re: DC Electric Motor

Quote:
 Originally Posted by kishor5466 this must be correct ,,,,,,, "I" at 6000 is 500A....
No.

Quote:
 Originally Posted by kishor5466 according to the formula given for "U" and the value of current, the motor will provide 206kw of energy right???
No.

Quote:
 Originally Posted by kishor5466 206kw of energy right???
#65
06-30-2012, 04:24 PM
 somanywelps Senior Member Join Date: Jan 2012 Posts: 432
Re: DC Electric Motor

Quote:
 Originally Posted by kishor5466 this must be correct ,,,,,,, "I" at 6000 is 500A.... according to the formula given for "U" and the value of current, the motor will provide 206kw of energy right???
Do you know how to read a graph?
#66
06-30-2012, 07:44 PM
 PStechPaul Senior Member Join Date: May 2012 Location: Cockeysville, MD 21030 Posts: 1,180
Re: Power rating of a motor

For electrical equipment such as transformers, overloads are based on thermal considerations and duty cycles. There is also the question of maximum temperature of the hottest spot in the device and what the insulation is rated for. So here is an example of overload duty cycle ratings. These are based on current overload, which is generally proportional to torque in a motor:

Continuous 100% duty cycle
1.4x 50% duty cycle 30 minutes ON 30 minutes OFF
2x 25% duty cycle 10 minutes ON 30 minutes OFF
3x 10% duty cycle 1 minute ON 10 minutes OFF
5x 4% duty cycle 10 seconds ON 4 minutes OFF
10x 1% duty cycle 1 second ON 2 minutes OFF

The duty cycle is based on the square of the current overload factor, because heat is based on the square of current when resistive losses predominate. There are also other factors to consider, so the device manufacturer should supply such information. The maximum ON times are determined by reading internal temperature during enginering specification testing, or they may be set by mechanical stresses due to high current and magnetic effects. An induction motor is limited by its breakdown torque. A series wound DC motor is limited by saturation and brush/commutator capacity.
#67
06-30-2012, 08:58 PM
 kishor5466 Member Join Date: May 2012 Posts: 43
Re: Power rating of a motor

Quote:
 Originally Posted by major Inquire of the motor supplier or test it yourself. Rarely if ever is an 8 or 10 second duty rating published for a motor. Again, what does your professor tell you?
Our professors don't help us in projects that's why i'm here to learn many things that apart from studies i can learn and also they are useful information for our project........
#68
07-01-2012, 03:57 AM
 major Senior Member Join Date: Apr 2008 Location: Ohio, USA Posts: 5,185
Re: Power rating of a motor

Quote:
 Originally Posted by kishor5466 Our professors don't help us in projects ......
Unfortunate. Perhaps this fact should be brought to the attention of the school's administration.

But there are the fundamentals which those professors should indeed be teaching you like:
Quote:
 Originally Posted by major You had better read a text book or ask your professor to explain the difference between power and energy.
Quote:
 Originally Posted by major Hello kishor, ......... And you are a student doing a university competition, correct? Do you not think you and your team should be using your faculty and own resources? ......... I don't mind helping a guy out, but teaching fundamentals to university students is someone else's job .........
I also notice that you have dropped the university association from your signature. Which school do you attend?

I like the SAE formula hybrid and other student competitions. I have been a member of SAE for many years in the Detroit section. I am also associated with a university and participate in organized student competition activities involving EVs.

I think that it is inappropriate for you or any student to use a resource like this forum to the degree which you attempt in your quest to obtain a design for your project. You are certainly welcome to read what is published here and to make an occasional query when you have done the background research and can phrase an intelligent question.
#69
07-02-2012, 12:51 AM
 kishor5466 Member Join Date: May 2012 Posts: 43
Engine and gear box separation

hey guys,
we have planned to use a Ninja 250r engine for our car...... We know that it's in unit production hence it comes with a gear box in a single casing and sharing the coolant ........... but we want to separate that gear box and put a different gear box??? is it possible??? are there any companies which do that????
#70
07-02-2012, 12:50 PM
 kishor5466 Member Join Date: May 2012 Posts: 43
selecting a motor for a drive

hi guys can any body suggest a dc motor of least weight for the following specifications

peak torque = 170Nm
Max. RPM = 3600
power = 60HP

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