[SOLVED] High frequency test signal in DC motor

[Guest]

tests on a dc motor

Hi all

I need help in the following situation. I need to inject a high frequency (kHz) signal in a DC motor while working. So, simultaneously we will have in the motor winding the DC current from the power source, and the AC signal that came from an AC source.

What are your suggestions? I thinking to use a toroid with its primary side connected to the AC source, while the secondary is connected in series with the motor winding. Is this a good solution?

Best regards
Pendragon

 

[IanP]

Wide-band toroidal transformer should work ..
You may need to add a capacitor on the dc side to close the loop for AC signal ..
I wouldn't rely on the DC power supply's 0Ω output impedance ..

Regards,
IanP

 

[artem]

What is frequency and level to be injected ? Is it for backemf sensing ? The toroid excitation must be avoided due to high motor current. May be air gapped core will be needed.

 

[Guest]

Hi

Motor current will be under 2.5 amps, and test frequency will be in the gap between 10kHz and 50kHz.

Thanks

Pendragon

 

[artem]

To be honest never did that. You can get idea from patents - enter on google string below :

"+back +emf +injection site:www.freepatentsonline.com"

Regards

 

[pilu.sandeep]

may i know what is the intent of injecting ac of such high frequency ?

 

[artem]

Hi

Motor current will be under 2.5 amps, and test frequency will be in the gap between 10kHz and 50kHz.

Thanks

Pendragon

Cant you do it by H bridge itself like it is done below for AC motor :
https://www.freepatentsonline.com/20070031131.html

 

[Guest]

Hi

I’m working with linear switched reluctance actuators. Motor phase inductance parameter change with mover position and phase current. From a finite elements software tool or experimental work, a map of L(i,x) can be obtained.
My idea is to measure the inductance and DC current, in real time, to know where the mover is.
Inductance can be measured using an low level AC signal. The mean value from the signal obtained multiplying the voltage across the inductance by the current advanced by pi/2 give an result proportional to the inductance.

If someone is interested in an more complete explanation please let me know.


Best regards

 

[artem]

as far as i understand you are interested in snapshot L value . BTW i dont how your actuator is energized , but if it is pem based - modulating falling time of pwm done outside of micro could be cheap solution for injection if micro is not powerful enough -
just OR the PWM output with 555 output (555 starts on falling edge) where 555's capacitor charging source is modulated by AC.