2017-04-18 05:07 AM
Hi,
When I am using the BEMF compensation configuration within the SPINFamily Evaluation Software, I input the Application Parameters and the Motor Parameters for my particular motor.
When I press the �Evaluate� button at the bottom right of the menu, the following Device Configuration Values are calculated:
KVAL_HOLD
KVAL_ACC
KVAL_DEC
KVAL_RUN
ST_SLP
INT_SPEED
FN_SLP_ACC
FN_SLP_DEC
These calculated values can then be written to the device and can be seen in the Phase current control tab within the �Device Configuration� menu.
How are the Device Configuration Values calculated from the values that I have inputted?
Is there a particular calculation that must be used?
Kind Regards,
Ernest
#dspin #dspin-gui #powerstep01 #bemf #pcc009v2-eval6470h-spinfamily2017-04-19 06:09 AM
Hi,
the calculations performed by the tool are the ones described in details into the
http://www.st.com/resource/en/application_note/dm00061093.pdf
.2017-04-19 09:55 AM
I came up with an alternative way to compute the motor parameters. It is here:
2017-04-20 07:39 AM
Hi Enrico,
Thank you very much for the information you have sent me in relation to the calculations. I found them to be helpful.
There are some further questions I would like to ask.
From the values I have entered I was able to calculate the Hold duty-cycle, Intersect Speed & Starting Slope perfectly.
I got a value of 30% for the acceleration, deceleration and run duty cycles instead of 46.5% (See below).
However I was unable to calculate the Final Slope Values (Acceleration & Deceleration).
Is it possible you could find the values which I am unable to calculate properly. The parameter values to input are shown below.
Thanks,
Ernest
2017-04-26 07:43 AM
Did you considered the conversion between rms current and peak?
Can you write your calculation?
2017-05-03 03:44 AM
Hi Enrico,
Sorry for my slow reply.
So these are my input values for the calculations
Supply Voltage (Vs)
12
Holding Current
0.2
Running Target Current
1.2
Electric Constant (Ke)
0.055
Phase Inductance (mH)
2.8
Phase Resistance (Ω)
3.3
Steps/Revolution
200
Acceleration/Deceleration/Run Duty Cycle
3.3*(1.2/12)*100 = 33
When you mention rms current to peak, should I just simply multiply my value by
√2, such as below:
(3.3*(1.2/12)*100)
*√2
= 46.672017-05-03 06:54 AM
Correct. The tool calculating the parameters look for the
rms current
, but the formula impliespeak current
value. So the conversation factor sqrt(2) should be applied. For holding current, considering the current is constant and not sinusoidal, the rms and the peak are exactly the same.2017-05-08 05:33 AM
I forgot to show you my calculations for the
Final Slope Values (Acceleration & Deceleration)
These are my input values for the calculations
Supply Voltage (Vs)
12
Holding Current
0.4
Running Target Current
1.5
Electric Constant (Ke)
0.0262
Phase Inductance (mH)
2.6
Phase Resistance (?)
2.4
Steps/Revolution
200
Acceleration/Deceleration Final Slope Equation
(2*PI*2.6*1.5+(0.0262/(200/4)))/(12)=2.04%
As you can see from the GUI below, the value calculated is 0.127%
I am using the following equation from page 10 of AN4144
Could you please tell me what mistake I am making with this equation?
Kind Regards,
Ernest
2017-05-12 03:05 AM
The correct formula should be:
(2 * pi * Lm *
Ipeak
+ Ke) / 4 / VBUS = (2 * pi * 2.6e-3 *1.5 * sqrt(2)
+ 0.0262) / 4 / 12In your formula I see following discrepancies: