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Hi,
I want to Know Q85 How to Calculate the Motor1 Current Input to ADC Offset Voltage Value. I am Using Eval-IM535 according to data Sheet EVAL-M1-IM535 evaluation design, which means 1 A motor current produces 25 mV voltage to ADC input, MCE_Wizard’ s “Motor1 Current Input Scaling” needs input of 25 mV/A.
Kindly Guide How to Calculate the value of Q85.
Thanks
Solved! Go to Solution.
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Hi @sohail
I suggestion you add the load first and then adjuet these parameters. PLLKp & PLLKi need to be adjusted based on load and Flx_M should be in range of 2048
Seen from the picture, The motor works well. Due to low motor current, noise accounts for a large proportion. It will be beter after add the load.
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Hi @sohail
1.First, Analyze the schematic diagram,see as below.
There are two resistance voltage dividing circuit:
a)5V->R27->R26->GND
b)5V->R27->R28+R29->RS1->GND
2. The circuit can be simplified as below:
we can get equation;
(V-V0)/2k + V/22k = (5-V)/220k
simplified ==>> V = 5/121+110/121 * V0 = 5/121 + 10/11 *V0
According to the virtual short of op amp, We can get:
Viss = V/2k * 22k = V*11 = (5/121 + 10/11 *V0) *11 = 5/11 + 10*V0
So, ADC Offset Voltage equal : 5/11 V = 0.454V = 454mV
Motor1 Current Input Scaling equal : 10*V0 = 10 * 0.0025 *I =0.025*I = 0.025V = 25mV (@ I=1A)
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Hi @LinGuohui
Thanks for Helping Parameter Calculation . Next Step is download parameter & As per First Step IM535 Reference is Current Wave Form.
10. Double click “VF Diagnostic” function in motor1 page, monitor motor current with oscilloscope. If motor
current is not sinusoidal, change target speed and Vd_Ext in VF Diagnostic sub-function, then double-click
“VF Diagnostic” until oscilloscope shows a steady sinusoidal current, with amplitude of 30~50% motor rate
current.
But I got On scope is this Very Bad Shape, I change Many Value in target speed and Vd_Ext in VF Diagnostic sub-function but No Sinusoidal Wave Form.
I Put Q83,84,85 as per you're Guide Line. I Remove Resistance as per Eval-Im535 board Guided line For IM-102T.
On Pin iss I am Getting 452mv which is Correct if motor Stop.
what step I am missing to Get Current Wave form no Sinusoidal.
Thanks
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Hi @sohail
What kind of motor do you use?
For VF control, There is no feedback loop,MCE only output SVPWM.
Therefore, The current waveform depends on your motor structure.
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Hi @LinGuohui
I am Using zws30-j dc brushless motor 30W.
When I use Double-click “Iu & Iv_Slow” in System page > Monitor Definitions, the motor current feedback would be very clean and sinusoidal, as shown in Figure 9, otherwise please tune “Gating Propagation Delay & Phase Shift
Window Size” in MCE Wizard. The sampled motor current noise amplitude should be less than 50 cts ~100
cts (below 5% of motor current, or below 5% of max AD range 2048 cts); otherwise, motor current sample
related hardware and setup need tuning.
“VF Diagnostic” sub function can verify:
• If motor is correctly connected
• If IGBT / MOS & gate driver work as expected
• If current sensing related parameters are correctly configured
• If PCB layout and DC bus decouple have been done correctly
After “VF Diagnostic” is done, click STOP button (the red traffic light button) to stop PWM
My Oscilloscope Shows this type of wave Form which is close to Sinusoidal.
but For Motor Current.
Double click “VF Diagnostic” function in motor1 page, monitor motor current with oscilloscope. If motor
current is not sinusoidal, change target speed and Vd_Ext in VF Diagnostic sub-function, then double-click
“VF Diagnostic” until oscilloscope shows a steady sinusoidal current, with amplitude of 30~50% motor rate
current.
I Got this Wave From
My Question in Both I am Running VF Diagnostic” function with Motor RPM 700 & Vd_Ext volts 90. Both Wave should be Sinusoidal?
Also motor Heat up very Hot.
Thanks
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Hi @sohail
This wavefrom is correct. Motor phase current shall be sinusoidal.
The other waveform is the effective value of motor current, which is the result of MCE calculation. So it is not sinusoidal and there are platforms.
For motor heat up, This is because you give too high Vd. Too high Vd will lead to too large magnetic flux of the motor and saturation of the iron core, thus generating large excitation current. Therefore, You should give appropriate V/F value.
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Hi @LinGuohui ,
Thanks for Last Email, Only one Last Adjustment is left. According to IM535 user manual .
Set target speed to about 50% of MAX speed, start “Iu & Flx_M” trace with “Auto Repeat On Level,” see
Figure 10. Flx_M is better within the range of 2000~2500 (rated value is 2048), and MUST be steady and DClike.
Some key tips for better motor-performance tuning:
• If Flx_M is not steady (swinging or oscillating), double-check motor parameters, speed loop PI gain, flux Estimator
time constant and PLL PI bandwidth (parameters PLLKp & PLLKi) related setup.
• If Flx_M is very noisy, double-check current feedback and Vdc-related hardware and parameters.
• If Flx_M is far from 2048, “Motor Back EMF Constant (Ke)” needs to be adjusted in MCE Wizard.
But my Iu & Flex as shown below FLex_m value is very Low. Motor Back EMF Constant (Ke)” is Define by Motor Manufacture if change this may be motor stop working.
My Question should I change Ke value?
How can Improve Iu wave form.
My Scope Result
Thanks & Kind Regards
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Hi @sohail
Sorry, the reply was not timely due to holiday.
But my Iu & Flex as shown below FLex_m value is very Low.
This is because the MCEDesigner setting is different. You can see the picture of IM535 user guide, Iu&Flx_M is count value. And your setting is real value. You can set it refer below.
For Iu wave form, This look like there is no load of motor. To get the best waveform, You must add load torque to the motor.
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Hi @LinGuohui
First of all I am very thankful to give Solution.
You are write I am Running the Motor without the Load.
My Flex value is improved know. Should I Add the Load or first Fine tune the Flex as per Im535 Instruction.
Some key tips for better motor-performance tuning:
• If Flx_M is not steady (swinging or oscillating), double-check motor parameters, speed loop PI gain, flux Estimator
time constant and PLL PI bandwidth (parameters PLLKp & PLLKi) related setup.
• If Flx_M is very noisy, double-check current feedback and Vdc-related hardware and parameters.
• If Flx_M is far from 2048, “Motor Back EMF Constant (Ke)” needs to be adjusted in MCE Wizard.
Thanks
Kind Regards
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Hi @sohail
I suggestion you add the load first and then adjuet these parameters. PLLKp & PLLKi need to be adjusted based on load and Flx_M should be in range of 2048
Seen from the picture, The motor works well. Due to low motor current, noise accounts for a large proportion. It will be beter after add the load.