The echelon wave to BLDC / square wave control, debug and choose proper lead role to be able to be below the condition that does not change main control algorithm, efficiency of pilot of apparent promotion electric machinery and shake noise level. Special to bringing sensor electric machinery, the lead horn in control sequential is equivalent to adjusting the sensor position of electric machinery interior, be equal to adjust the result of sensor physics position at the means with inconvenience or difficulty through coming true with the software method that goes easily simply thereby.

 

1, three-phase BLDC controls a principle (echelon wave)

 

Next graphs expressed not to have the fundamental that brushs wave of electric machinery echelon to control algorithm. Above all, alternating current commutate is volts d.c. , class is frequency conversion part after (Inverter) , include 6 switch parts of an apparatus or appliance (FET) : Go up the U of bridge arm, V, W and the X of arm playing the bridge, Y, Z.

 

According to proper sequence control these FET switch parts of an apparatus, for instance:

 

1: U->Y

2: U->Z

3: V->Z

4: V->X

5: W->X

6: W->Y (assume electric machinery direction is turning)

 

So electric current can have shed electric machinery coil according to the order below:

 

1: U photograph arrives V photograph (U->V)

2: U photograph arrives W photograph (U->W)

3: V photograph arrives W photograph (V->W)

4: V photograph arrives U photograph (V->U)

5: W photograph arrives U photograph (W->U)

6: W photograph arrives V photograph (W->V)

 

In all 6 paces, circulate so. (like the graph 1 is shown)

 

Graph 1

 

Manage together, if electric machinery direction is,invert, criterion switch order is:

 

1: U->Z

2: U->Y

3: W->Y

4: W->X

5: V->X

6: V->Z

 

This does not have the echelon wave that brushs electric machinery BLDC namely / square wave control is algorithmic.

 

2, three-phase BLDC controls sequential

 

Without the control that brushs electric machinery sequential relies on position of electric machinery rotor, show lead character to go to the lavatory / guide current flow angle, here is with bringing the electric machinery of suddenly Er sensor exemple. According to suddenly Er the position of chip is judged, feedback should is interrupt. Every detect to an effective Huo Er positional signal codes (Pattern) , begin commutation to arrive next, begin to detect then next the next time positional feedback is interrupted. Pursue as follows 2. According to afore-mentioned 6 paces the order of ceaseless commutation:

 

1: U->V

2: U->W

3: V->W

4: V->U

5: W->U

6: W->V

 

Recycle move back and forth.

 

Graph 2

 

Detecting every time when Pattern of suddenly Er position, the wide modulation of arteries and veins that commutation outputs correspondence (PWM – Pulse Width Modulation) Pattern. Later, to the position feedback signal begins sampling monitoring, until detect again Pattern of effective suddenly Er position.

 

Signal of switch of the PWM in the graph (U~Z) area piece is medium black effective n, embedded PWM carrier wave (arrive from a few K a few KHz, duty is alterable) . The phase voltage in the graph (photograph of U photograph ~W) medium black is narrow columnar and undee be in this commutation hour (from now on one pace switch arrives next PWM Pattern) , wait for a reason as a result of follow on current (the inductance of electric machinery coil) the commutation tension that create jumps change.

 

3, lead horn

 

In without brush dc machine (BLDC – BrushLess DC) regular meeting of the classics in control uses Lead Angle, namely lead horn / guide current flow angle. Because electric machinery coil is perceptual load, the to load voltage that goes up at coil relatively so, the electric current in coil can have certain when delay, affect the efficiency of electric machinery and generation noise thereby. With citing of phase voltage of electric machinery U, on U of graph PWM signal, X and weaveform of U phase voltage magnify, pursue as follows. Among them U photograph spreads out can see actual voltage is undee, embedded PWM carrier wave. Oversight PWM carrier wave sees the picture that include sth resembling a net, following graphs 3 most below undee place is shown.

 

Graph 3: The actual voltage when U photograph spreads out is undee

 

Here, place of green dotted line is commutation dot, the definition is lead horn / guide current flow angle is nodded 0 degrees. Be located in right of phase voltage midpoint at this o’clock (behind) 30 degrees. And horn of Lead Angle lead / guide current flow angle, just as its name implies is gone to 0 degrees from lead horn namely left (forth) ahead of schedule how many degrees.

 

Generally speaking, do not have especially brush wave of echelon of electric machinery BLDC to control algorithm, in electric machinery circumstance of high rotate speed falls, signal is inputted to 6 PWM before needing to be nodded in every commutation (U~Z) the part of Lead Angle lead with be inserted certain / guide current flow angle, graph 4 it is different lead horn / guide current flow angle, from 0 degrees, 7.5 degrees, 15 degrees go to 30 degrees, place inputs signal correspondingly respectively.

 

Graph 4

 

Lead horn / guide of current flow angle debug depend on voltage of parameter of electric machinery itself, electric machinery and electric machinery rotate speed. General from experience for, to identical electric machinery, be in given below voltage, the rotate speed of electric machinery is higher, need taller lead part so / guide current flow angle. The crucial method that debugs appropriate Lead Angle takes laden case in electric machinery namely, in interested working rotate speed (or limits) next finding out electric machinery efficiency is highest (output power / power input) , electric machinery noise and shake the least state of affairs.

 

For the electric machinery of sensor of suddenly to taking Er, the physical position that adjusts suddenly Er sensor (correspondence arrives electronic angle) also can have similar effect. And generally speaking, suddenly Er sensor is located in the PCB inside electric machinery board on, adjust not quite easily. On the contrary, through adjusting role of Lead Angle lead / guide current flow angle, want angle of corresponding good physics and electronic point of view only (depend on of electric machinery rotor extremely logarithm) relation, also can have the effect of position of physics of sensor of suddenly Er of interior of similar correction electric machinery, carry the software kind that goes easily simply thereby (lead horn / guide the adjustment of current flow angle) implementation is equal at adjusting the result of sensor physics position with inconvenience or mixed pattern.