"DC Fan" HALL sensor placement may cause unreasonable adverse commutation, speed instability ﹑ low efficiency, easy to produce dead point, the size of the wave, noise and other shortcomings. If N (S) rotary blades on the pole to Hall Element, but not sensitive to the Hall IC Brp (Bop) while transfer state, the tape and the coil at this time four-pole magnetic field that is a result of suction and stops rotating, the formation of the so-called dead. In this case the Hall IC sensors should be enough, the tape magnetic field is too small, or poor position Hall IC caused, improve part of the tape cassette can be seen from Figure III of the magnetic field distribution in the Hall IC at the same position, the tape will be charged increase the value of the magnetic pole conversion zone angle decreases, can be advantageously induced in part by improving the position of Figure III shows that Hall IC sensors should be shifted to point Bop, Brp place to induction, it should happen if dead Hall IC pole position biased transition area, thus allowing the Hall IC position slightly to the right to reach Bop, Brp position to improve dead, another Hall IC tape nearer to the induction of the stronger magnetic field, so the closer the Hall IC tape, the improvement effect will be more significant, is not enough in the Hall IC sensor can switch to a better part of the induction of the Hall IC can be. In order to ensure the normal operation of the fan, the proposed position of the IC should be ahead of the commutation point.