jur wrote: ↑
Nov 07 2018 6:01pm
andyme wrote: ↑
Nov 07 2018 4:32pm
Ok, this is something that i do not understand: that a motor has torque - ok, that it has power - also ok. But how can it have speed? (and i am not talking about the fact that it is mounted and fixed to a bike
For my understanding, the motor helps you pedalling (assuming that you do not use it like a motorcycle). so the speed comes only from the rider. The point is only that thru the help of the motor, the rider is able to achieve the required speed, while without the motor it would be beyond his forces. So i see the motor as a supplier of torque, because this is what makes pedalling easier.
Maybe you can explain to me what i got wrong here.
The reason that rotational speed is also a factor, is because as the rotor rotates, the rotor magnets generate a voltage on the field coils that is effectively opposite in polarity to the voltage applied by the controller (called back EMF). The higher the rotational speed, the bigger the back EMF. So at a critical speed, the generated back EMF is equal to the maximum voltage the controller applies, and at that critical speed, no current flows in the field coils, resulting in zero torque.
So, as the speed increases, the back EMF increases as well, resulting in lower torque generated with increasing speed.
wow...ok...this is really deep knowledge...With all due respect, i think this surpasses the comprehension of many people, at least it does surpass mine.
Can you please maybe explain terms that are commonly used, because i think these are the terms that many people are used to: I am talking of Watts, Volts, Amps.
Was I wrong in saying that a 48V motor can be "stronger" (i.e. have more Watts/ Horse Power) than a motor with 36V? provided both motors have the same maximum current value?
Can it really be in real practical life, that a 36V motor will actually have advantages over a 48 V motor? especially since we have customizable software?
By all means i am not being cynical, these are sincere questions.
If i take cars for example: where and when would a car with 100 HP be superior to a car with 200 HP? even more if the motor characteristics are being controlled by software/firmware?
So therefore, not knowing what you know, i have a real problem to understand if and why and when a 36V motor could perform better than a 48 V motor no matter how bad he tries (meaning: how well the firmware may be adapted)
so: what would really be a good reason to prefer a 36V motor over a 48 V motor