Sensorless brushless dc motor control - back emf method

Stator Motors Rotor
Specifications
1. 20 years manufacturing experience
2. competitive price,high quality

"The potential laws" is by far the most mature, the most effective, is also the most common and most widely application a rotor position signal detection method. The basic principle of this method is to ignore the influence of fan motor permanent magnet brushless dc motor armature reaction, by detecting "disconnect" (inverter bridge power device is up and down in that phase) off of the back emf zero, in order to get the rotor's six key position signal, and use this as reference, in turn trigger conduction six power tube, drive motor running. This method is often used in the wholesalemotor.blogspot.com armature winding adopts y connection of "three phase six - 120 ° square wave type" driven permanent magnet brushless dc motor (because of square wave motor is just a number of discrete key rotor position signals). 

Y series totally enclosed protect Asynchronous motor
Specifications
1. 20 years manufacturing experience
2. 12 months guarantee
3. low noise and temperature rise

4. high starting torque
Figure 1 (a) and (b) are given a Taipei wave motor of main circuit, the back emf waveform and trigger a composite state of inverter power devices. The figure 1 (b) shows that at any moment of the inverter power supply, there is always a in ac motor the upper and lower bridge arm are in the off state, namely the phase winding motor is impending, so the phase voltage is equal to the induced potential of the phase winding. In ignore the armature reaction of air-gap magnetic field under the lamination premise of the impact, can be thought of the induced electric potential is equal to the phase winding back emf. Detecting the back emf zero moment, and delay, if appropriate, can get the right trigger time of power device, and the electric potential zero point can be obtained by phase voltage of the voltage or testing.