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Mechanical Engineering
Which prime mover do you think will win?
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[QUOTE="Altrepair, post: 5477273, member: 174712"] Sorry, not trying to be rude. The answer is the DC electric motor will win and lift even the highest load of 135Kg. PM DC motors have inverted parabolic power curves that max at 50% efficiency and linear increasing torque curves that max at stall where max current is reached when the current is limited to the resistance of the motor's armature windings and other associated parts of the circuit with the voltage applied. When the load increases the armature will slow down (rotor part), which in turn causes the back EMF generated to go down resulting in the differential voltage going up that is applied to the resistance of the armature circuit, which causes current to increase (Vsupply - BEMF), and since the magnetic field is proportional to the current (there will be magnetic saturation as current gets very high), the magnetic force will increase more and more that is multiplied with rotor radius to give more and more torque. If I need to explain max power transfer theorem to explain why peak power occurs at 50% efficiency in a brushed DC motor then let me know. Internal combustion engines cannot increase in torque and power when you overload them. The reason is there is no mechanism in a combustion engine to ram in more fuel/air mixture once the power stroke has commenced. Thus, if load where to increase during the power stroke phase, then the explosive force produced will not be able to over come the force required to move the piston. So you get a stall condition. I don't think its even possible to design a combustion engine that can add in more fuel/air mix "on-the-fly" during a power stroke. It would be very difficult to do without losing compression. Lost compression during a power stroke will mean less explosive force against the piston face. The problem is exacerbated more if the the load demand increases on the other cycles where the fly wheel is having to release the stored energy to carry the piston through those cycles where power stroke does not occur. [/QUOTE]
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Which prime mover do you think will win?
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