Application of Blocked Force Methodology in NVH development of Electrical Machines



To determine excitation forces of electrical machines from measurements, Transfer Path Analysis is commonly used. Transfer Path Analysis yields input forces indirectly utilizing measured responses and transfer functions. When conducting transfer function measurement, it is recommended that the source of excitation is mechanically isolated from the receiver structure. However, in practice this is difficult to achieve without affecting the transfer path itself.

The concept of the Blocked Force method introduces blocked forces which are independent of the receiver structure, thus allowing measurement of transfer functions without isolating the source.

In this research, a stator / rotor assembly is considered as the source.  This assembly is bolted to a test-housing, considered as the receiver. Blocked forces are determined at the mounting locations between stator and test-canister. The correctness of the calculated blocked forces is verified by comparing the predicted and measured responses at selected target points which were not used for determining the blocked forces.