# Maximum torque, maximum power

1. Jun 15, 2007

### phigit

Explain why the torque developed at maximum power is less than the maximum torque

maximum torque of 165 Nm at 4300 rev/min and its maximum power 88 kW at 5500 rev/min

Torque developed at maximum power
T = bp x 60
2pN
= 88000 x 60
2 x p x 5500
= 152.8 Nm

Power developed at maximum torque
bp = 2pNT
60
= 2 x p x 4300 x 165
60
= 74298.66626 ÷ 1000
= 74.3 kW

please help i'm really not sure!

2. Jun 15, 2007

### Chi Meson

I don't know what the problem is.

152 is less than 165,

isn't it? There's no need to do anything with the second equation here, you're done.

3. Jun 15, 2007

### phigit

it's necessary to explain why and why the loss occurs though.

4. Jun 15, 2007

### andrevdh

The rotational speed is still low when the maximum torque is applied at a lower gear ratio. As the speed picks up you change over to a higher gear and you can then apply less torque.

5. Jun 15, 2007

### Chi Meson

The answer (as given by andrevdh) cannot be deduced through the math in this particular problem, so there is no formula to prove it. Motors and machines will have several factors that affect their efficiency of energy transfer.

6. Jun 15, 2007

### andrevdh

Could it be due to (rotational) inertia - that is the rotational speed peaks at a later stage than the applied torque?

Am sure the motor enthusiasts have discussed this to great lengths ... and still have not come to a conclusion.

7. Jun 15, 2007

### Chi Meson

I think you were right with your previous post. I meant to say to the OP that your answer was not observable by looking at the given quantities; rather, it required knowledge of how motors and gears worked.

8. Aug 11, 2008

### rodeliocueva

maximum torque is develo

the torque developed is low at maximum power because of many other thing that helps your torque reduce when power is increased,
one example is when you start the engine, during starting you need more torque to turn your engine, but once your engine is running the torque is reduce because of to many factors, first is the momentum of your flywheel that helps the shaft to turn faster, second is friction will be reduce between shafts and bearing, and third is the speed, once your speed is built up your shaft is almost floating from the bearing which reduces the friction a lot.

9. Mar 29, 2010

### cyborgk

LOL phigit you got a exact same question at my, r u doing IMI course?

and your answers above are same as me.

p/sps, not seeing the date from 2007

Last edited: Mar 29, 2010
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