Of course this is an oversimplified explanation, but it should be enough for you to understand the principle behind motors with brushes. The brushes are always set to the same polarity, but since the contacts will move together with the motor the polarity will be reversed whenever the motor spins 180°. The ends of the wire that is wrapped around the motor are attached to two contacts (also called “commutators”) and two brushes touch these contacts. The easiest and cheapest way to accomplish this is by using a pair of brushes. If your room size is in between the sizes in the chart, 'Bigger is Better'. If the fan is further away from the seating area, you may need a much larger fan where the blade tips are closer to the area where you need to feel the breeze. So, for the motor keep continuously rotating, we need a mechanism that will automatically reverse the polarity of the wire right after the motor spins 180°. If the fan is directly over the seating area, choose a fan that is within 2 or 3 feet the diameter of the space. By reversing the polarity, the magnetic fields generated by the motor will also be reversed, creating again the same situation we had in the first step, moving the motor 180° on more time. However, after the motor moves 180° pushed by the repelling magnetic forces, it will stop, because the system will now be equalized: since the motor spun, now the magnetic fields generated by the motor will be of the opposite type of the magnetic fields generated by the stationary magnets, making the motor to be attracted by the stationary magnets instead of being repelled.įor the motor to rotate again, the direction of the current applied to the wire must be reversed.
We illustrate this situation as the “first step” in Figure 1.
Also, the magnetic field presented by the opposite magnet will be the opposite, attracting the electromagnet. When the magnetic field generated by the electromagnet is the same as the magnetic field generated by the stationary magnet, the motor will move, because identically labeled magnetic poles repel each other. Around the motor there are two big pieces of curved magnets, one producing a north magnetic field and the other producing a south magnetic field. When energized, this piece of metal is transformed into an electromagnet, generating a magnetic field with two poles (labeled north and south).