1. Test Fixture to Measure Saturation Characteristics of Coupled Multi-winding Inductors
Name: Marzieh Karami, Xuechao Wang, Ranga Tallam and Robert Cuzner
Spring 2018

2. Introduction
Drive output L-R filters: Three-phase inductor with CM and DM inductance provides an integrated solution for CM and DM filtering, for reflected wave over-voltage reduction, cable charging current reduction.
DC link inductors: that are currently used are designed for DM filtering; they have integrated CM impedance and provide filtering for CM currents.
In order to accurately characterize coupled multi-winding inductors, saturation characteristics of DM (CM) impedance must be measured in the presence of CM (DM) currents.
- For output L-R filters, if DM current nearly saturates the inductor then it will provide effective filtering for CM currents.

3. Prior Art Solutions Existing Solutions: Disadvantages:
Applying pulse voltage to measure DM inductance for each phase;
Connecting three phase inductor with a three phase variable voltage power source for measuring the CM and DM inductance
Disadvantages:
Both method requires high voltage or high current source which is not available for large inductors.
DM (CM) current can affect the saturation of CM (DM) inductance significantly. Therefore measuring the inductance without both DM and CM current can be ineffective.

4. Prior Art Solutions
Simulation of each choke in FEA software (e.g. ANSYS Maxwell) to get Saturation Characteristics
Disadvantages:
Accurate geometry information about the choke and material properties are needed. The core material, number of turns and all dimensions must be known.

5. Fixture to Measure CM Inductance with adjustable DM bias current for a DC link choke
Isolation
High step-down ratio
Adjustable DM bias current (DC) is applied, with a pulse source providing the CM current

6. Fixture to Measure DM Inductance with adjustable CM bias current for a three-phase AC line inductor
ICM/3
Adjustable CM bias current (DC) is applied, with a pulse source providing the DM current

7. Experimental Test Results – DC Link Choke
Ch2 and Ch1: Pulse Voltage 200 V/div
Ch3 and Ch4: Choke Currents 5 A/div
50 us/div
Measurement of saturation characteristics of CM impedance with DM current bias applied

8. Experimental Test Results – DC Link Choke
Saturation Point

9. Experimental Test Results – 3-phase reactor for drive output LR filter
3-phase inductor used in drive output LR filters provides combined DM and CM inductance

10. Experimental Test Results – 3-phase reactor for drive output LR filter
Ch2, Ch3 and Ch4: Choke Currents 10 A/div
Ch1: Pulse Voltage 200 V/div
50 us/div
Measurement of saturation characteristics of DM inductance with CM current bias applied

11. Experimental Test Results

12. Thank you!