Dear Naresh,

I suggest to limit the amplitude of final voltage vector, formed by d and q axis voltage. It means v = sqrt(v_d^2 + v_q^2). Limiting of only one voltage component may still cause that final voltage will be out of the inverter limits.

Thank you Mohammad and Viktor.

Mr. Viktor. You are right. But when I am limiting the voltages, say V_d, I will reduce

V_d = sqrt(V^2 - V_q^2). By doing so I can ensure that resultant V is equal or less than Inverter limits.

But what i wanted to know is how Vd and Vq would effect the Torque and speed performance of the motor.

Hi Viktor,

Could you please explain to me how you have arrived at the conclusion that, resultant voltage can still be higher after limiting one of the individual components?

Thank you

Hi Naresh,

I didn't know that you also reduce the other component, than you limit (in fact, this limits both components in some way so voltage won't exceed inverter limits, as you already wrote). However, to answer the question about voltage effect, voltage V_q is the one, that has to be larger then back EMF voltage (Ke*w). Thus, if motor runs without load, V_d is held on zero whereas V_q needs to compensate Ke*w (for example V_q = 6.6 V for my motor). If you then apply load, V_d changes to some negative voltage ( V_d = -4 V in my case) and V_q will be slightly larger (V_q = 7.7V) .

Hope this helped

Hi Viktor,

Thank you for the detailed answer!. I understood it perfectly! :) :)