Baidu explains the principle of common mode inductance more clearly than I do:
100% Single Pulse Avalanche Energy Test Lead free Compliant with EURoHS 2011/65/EU Directive
Product applications: Load switch PWM application power management
Product applications: Battery protection, load switch, uninterruptible power supply
Common mode inductors are key components in switching power supplies used to suppress common mode noise.
In practical applications, the selection and evaluation of common mode inductors need to consider the following key parameters: