Using 1 shunt resistor for field oriented control of BLDC motor

[ashugtiwari]

Hello All,
I have been through different app notes and online theories on BLDC motor field oriented control. All of them uses per phase shunt resistor for current sensing and uses current in two phases to calculate last phase current and then use transform to convert the currents to dq vector of rotor. I have a board where only 1 shunt resistor is connected between the ground and common point where all lower mosfet's of half bridge is tied together. Can I still implement the field oriented control in this board?

Thanks
Ashutosh

 

[KlausST]

Hi,

I don´t think so, because it is a mixture of currents and doesn´t represent phase current. Neither amplitude nor phase angle.

Klaus

 

[schmitt trigger]

All the BLDC control boards I've ever seen, use two current sampling resistors.
Otherwise, without the magnitude and phase information obtained by those two current vectors, how can you resolve the third?