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Why does changing the polarity on a DC motor cause the motor to change directions?
Of course, the direction of current is controlled by the polarity of the voltage. So in order to change the direction of rotation, we can simply reverse the voltage, causing the current to flow in the opposite direction, changing the force by 180 degrees and the motor to be driven ‘backwards’.
How does a motor change polarity?
Your DC motor can be configured to turn in either direction by simply inverting the polarity of the applied voltage. The change in the flow of current switches the direction of the spinning force, causing the motor’s shaft to begin turning in the opposite direction.
Why is it important to change the direction of the current in a motor?
The swinging change of voltage is important because of the basic relationship between magnetic fields and electric currents. When a conductor (such as a wire) moves through a magnetic field, the magnetic field induces a current in the wire.
What happens when the polarity of a motor is changed?
If one phase has the polarity changed, then the magnetic field distribution within the motor winding becomes uneven, and the output torque will “pulse”. (To see this for yourself – plot the three phases and their sum on a single graph. Then switch the polarity on one phase and see the difference in the waveforms.)
Why does a DC motor rotation change when the battery is reversed?
To reverse the motor, you need to change the polarity of the supply voltage to either the field winding or the armature winding, but not both. Generally it is better to reverse the field voltage because the field current is less than the armature current, so your reversing switchgear is more lightweight.
How does voltage affect the speed of a DC motor?
Whereas the voltage polarity controls DC motor rotation, voltage magnitude controls motor speed. Think of the voltage applied as a facilitator for the strengthening of the magnetic field. In other words, the higher the voltage, the quicker will the magnetic field become strong.
Why does a motor not move at low voltage?
Each motor will have their own voltage/speed curve. One thing I can guarantee from each motor is that at very low voltages, the motor will simply not move. This is because the magnetic field strength is not enough to overcome friction. Once friction is overcome, motor speed will start to increase as voltage increase.