Example 6: 3-phase choke for mains filter

To measure the inductance of 3-phase chokes the 3-phase Extension Unit as an additional unit for the Power Choke Tester DPG10 series is necessary. A single phase measurement without the 3-phase Extension Unit would lead to wrong measurement results due to the different flux conditions in the core.

In this example a 3-phase filter choke made of grain-oriented electrical sheet is shown. The continuous rated current is 65 ARMS, the weight is approximately 35 kg. In contrast to most other 3-phase chokes the inductance of all three legs is nearly the same at this choke due its special construction. At most 3-phase chokes the inductance of the outer legs is several percent lower than the inductance of the middle leg due to the unsymmetrical core geometry.

To make routine testing easier during production, minimum and maximum limit curves can be defined. If the measured inductance curve falls within the range created by these two limit curves, then the test component is passed, if not then it is failed.