reverse saliency , i.e. positive d-current in Flux or FluxMotor; d-axis inductance bigger than q-axis in spoke type PMSM

Melih Ayyildiz_21808

Hello,

I am researching on the spoke-type PMSM. This motor has the specialty that it's inductance in d-axis is bigger than in q-axis. To my knowledge, this is mostly the other way around for all the other interior-magnet PMSM. 

I found an scientific paper which talks about this topic and states, that a positive current in d-axis is needed at the base speed point rather than negative d-current. I wish I could upload a picture from the paper but unfortunately it is not a open article. You can access it via the hyperlink.

I designed a motor with the Spoke01C template and indeed, L_d was bigger than L_q at the base speed point. The ratio Ld/Lq is around 2. This was calculated within FluxMotor with the Datasheet - Motor - Current-Voltage Test. I am now curious because the "performance mapping - sine wave" test noted that only negative d-current is needed to run the motor. 

My Questions:

1. Is FluxMotor or even Flux capable of recognizing this effect, i.e. that positive d-current is needed to run the motor?
2. Does this phenomenon have an impact on the calculations in flux/FluxMotor? I analyzed the motor within Flux and also within FluxMotor for the base speed point according to the I-Psi-N Test. I also exported a Flux model and calculated the machine characteristics there. According to the helpsite of FluxMotor, a positive angle for Psi results to a negative d-current. Does this affect to the output torque? I am asking this because according to the upcoming formula, for (L_d-L_q)>0 and a negative d-current, my torque would actually decrease.

I am fairly new to these topics. Let my know, if I have not explained it well enough to understand my issue.

 

 

fzidat

Hello Melih;

Saliency is dependent on the rotor shape as you mentionned:

 

 

Flux will compute always something depending on the input you use, so it is up to you use the right inputs to have the right outputs.

 

Concerning FluxMotor:

- For PM machine, there will not be positive Id in Motor mode computation

- For synchronous reluctance machine, Id is always positive

- For wound field synchronous machine, both positive and negative Id will be possible

 

I hope i answered your question

 

Regards