On the other hand if you get a different motor that can provide the same torque with 3v rather than 6v you will probably find that it needs more current because it will probably have fewer turns in the motor coils. If you have a specific motor and if you reduce the voltage from 6v to 3v then you CANNOT get the same current int he motor, never mind getting double the current. Note - above green text added following the helpful comments in Reply #11 The website said that reducing the voltage to 3 would double the current to maintain the same torque values.Īssuming you want the motor to run at the same speed with either voltage then what is missing from that is the role of voltage in "forcing" the current through the motor. There are a few motors I am interested in working with a project although they only show the 6V values. In an ideal motor the torque is proportional to currentīased on this, it sounds like the websites suggestion of "half the voltage, double the current to maintain the same values" was in reference to maintaining the same speed.īut if I half the voltage, doubling the current should only increase torque, not speed correct ? Theretore the website was incorrect in which values are affected by the current.Īs they said the torque will stay and speed will increase but that's impossible if voltage is proportional to speed It appears most 6V motors can move this amount at the speed I need. I am trying to accomplish this using a fixed 3.7V battery system. Power is the product of speed times torque.īased on the above, I believe the answer I was looking for is įind a motor with the correct torque, appropriate current, but 2x the speed at 6V I can just feed it 3V to bring it to my speed needed and maintain the same current and torque values.The goal is to be able to transport a fixed weight, at a fixed speed. Remember all units are SI, so angle in radians, torque in Nm or J/rad, angular velocity in rad/s Its the same k, the motor constant (a property of the motor and its windings). Torque = k x current, which implies voltage = k x angular velocity. Also in an ideal motor the torque is proportional to current, so we get Thus voltage x current = torque x angular velocity Often mechanics calculations are simpler if done in terms of energy.įor our electric motors we can consider the electrical energy change is approximately the mechanicalĮnergy change (for a quality DC motor at least!), so we can equate voltage x charge = mechanical energy. Newtons are joules/metre, and hence newton-metres are really just joules (ie the idea ofĪngle has dropped out of our units) - thinking in terms of joules/radian avoids that. I suggest the conceptually clear way to think about torque is in joules/radian, but in practice we use Is the change in energy per unit distance. Torque is the change in energy per unit angle. Sure, we can make it more complicated than the above but is that really necessary? "a twisting force that tends to cause rotation"
0 Comments
Leave a Reply. |