![Page 1: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/1.jpg)
Current Sensing Investigation
End of Internship Presentation
John Zhang
![Page 2: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/2.jpg)
What is Current Sensing?
• To measure current flowing through a conductor
• Typical Approaches:
– Shunt resistor
– Current Transformer
– Hall Effect
Shunt resistor approach:Measure voltage drop across a small resistor.
Step down primary current
Current => Flux => Voltage
![Page 3: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/3.jpg)
Hall Effect Current Sensing
• Physics:
– Lorentz Force
– Uneven Distribution of Charges
– Electric Field & Voltage
• Closed Loop Hall Effect Sensor
– Feedback circuit to drive flux to 0
– IF related to Iin by turn ratio
![Page 4: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/4.jpg)
Why is Current Sensing Important?
• Field Oriented Control: Control of flux-producing (d-axis) and torque-producing(q-axis) currents.
• Sensor quality directly impacts output dqcurrents hence machine torque.
• Also used in sensorless control to determine rotor position
![Page 5: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/5.jpg)
Flux Concentrators (Cores/Toroids)
• Function: Concentrate flux by having a high permeability (B (flux density) = u (permeability) * H (field strength) )
– Permeability of Air ~= 1
– Permeability of 4% SiFe ~= 2000 - 35000
Current in BussBar Magnetic Filed (H) Flux Density (B) Hall Voltage
Ampere’s Law Permeability Hall Effect
![Page 6: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/6.jpg)
Core Properties
• Electrical:
– Permeability (Gain)
– Saturation
– Hysteresis
Desired Linear Relationship
Cores I investigate:
O.D = 31.07 mmI.D = 17.4 mmGap = 5.14mm
![Page 7: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/7.jpg)
Core Saturation
• In saturation, core permeability decreases significantly
• Can cause major torque ripple issues
-2500
-2000
-1500
-1000
-500
0
500
1000
1500
2000
2500
-1.50E-02 -1.00E-02 -5.00E-03 0.00E+00 5.00E-03 1.00E-02 1.50E-02
1400Arms 13MM gap core saturation Actual(red) vs Measured(green)
![Page 8: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/8.jpg)
Core Hysteresis• Generally a nonlinear effect
• For our test results, a delay model can approximate the effect
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-6.00E-04 -4.00E-04 -2.00E-04 0.00E+00 2.00E-04 4.00E-04 6.00E-04
Hysteresis : Actual (green) and Measured (red)
![Page 9: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/9.jpg)
My Project: Core Evaluations
• Goal: Compare the saturation and hysteresis characteristics of Tape Wound (TW) cores and Stacked Lamination(SL) cores
Note: Comparison is for 38533 PN CoreGap = 5.15 ± 0.4 mmRated current: up to 250 Arms (354 A peak)
Cost Saving:
TW 38533 $0.99Stacked Lam cores $0.348Annual volume ~150,000
Potential Annual Saving from cores ~= 96,300 !
![Page 10: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/10.jpg)
Benchtop Core Comparison
Old Setup:- Larger Center Conductor (0.62 inch d)- Difficult to position cores and sensors => flux to current conversion gain changes due to mechanical vibration
New Setup:- Smaller Center Conductor (0.5 inch d)- Sensor position stable => more consistent gain
Core I.D = 0.68 in
![Page 11: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/11.jpg)
Benchtop Core Comparison
• Main Comparisons between cores:– Hysteresis vs frequency– Hysteresis vs current– Saturation
• Other Considerations:– Sensor Type: Lakeshore Gaussmeter vs Hall Bridge vs
Allegro/Melexsis– Setups
• Center conductor diameter – affects B field• Mechanical – position affects results
– Gain error (calibration)– Variances between cores
![Page 12: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/12.jpg)
Hysteresis vs Freq
• Experiment:
1. Put ~250Arms current through center conductor at 100Hz, 250Hz, 500Hz.
2. Measure gap flux with Lakeshore gaussmeter.
3. Convert gap flux to current measured.
Gain = Irms / Brms.
4. Plot Current Sensing Error vs Current in conductor
![Page 13: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/13.jpg)
Hysteresis vs Freq Results
SLTW
- Spikes due to LEM problem- Differences between cores insignificant at this current level
![Page 14: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/14.jpg)
Hysteresis vs Current Level
- Stacked Lam core slightly worse hysteresis at each current level- At 500Arms @ 500Hz, SL cores have worse hysteresis with max current error ~= 10A.
TW cores have max current error ~= 5A. This current level is x2 rated current for this core!
100 Arms – 500 Hz 200 Arms – 500 Hz 500 Arms – 500 Hz
![Page 15: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/15.jpg)
Core Saturation Comparison (800Arms 500Hz)
TW SL
- SL slightly more error before saturation- SL softer saturation (limited operating range)
- Does not appear to be an issue for the 38533 part at rated current levels- Gap tolerances for SL are significantly tighter- Prudent to further evaluate any additional higher current replacements
![Page 16: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/16.jpg)
Hall Sensor Evaluation
• Compare LEM(closed loop hall effect), Hall bridge, Lakeshore Guassmeter, Allegro and Melexsis
LEMLakeshore
Hall BridgeAllegro
Melexsis
![Page 17: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/17.jpg)
LEM vs Lakeshore Gauss meter vs Hall Bridge
LEM
Lakeshore Hall Bridge
Significant delay in the hall bridge signal output.
Hysteresis appears similar to a delay under steady state conditions.
Difficult to distinguish between sensor delay and core hysteresis.
![Page 18: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/18.jpg)
Lakeshore(L) vs Hall Bridge(R) SL cores
- Current sensing error due to a fixed delay is proportional to freq of operation.
![Page 19: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/19.jpg)
Lakeshore vs Allegro
• Allegro sensor performance close to Lakeshore
LEM
Lakeshore
Allegro
![Page 20: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/20.jpg)
Lakeshore vs Melexsis
• Melexsis slightly less delay than Lakeshore
LEM
Lakeshore
Melexsis
![Page 21: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/21.jpg)
Core Evaluation Conclusion
• PML Core samples are substantially similar during normal operating conditions
• Recommend tooling production candidates with PML
– Requires some further mechanical and electrical evaluation
![Page 22: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/22.jpg)
Further Work
Even with existing current sensors, Iq/Id currents can be quite noisy!• Explore quantization effects and other noise in:
– Position sensor– Current sensors– Rotor harmonics (PMAC)
Currents:20A/Div
![Page 23: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/23.jpg)
Simulation Results
No Theta_e error. No sampling
w/ current quantizer2V encoder output 5V 10-bit ADC
w/ better quantizer2V encoder output3.3V 12-bit ADC
![Page 24: John Z Internship Presentation_w_animation_NBedit](https://reader034.vdocuments.us/reader034/viewer/2022052608/587a796c1a28abf0468b5ab7/html5/thumbnails/24.jpg)
Thank You!
Questions?