The TrafoSTART is an electronic relay for the switching single-phase transformers. The magnet- ization of the transformer core is maintained in limits during energization. The transformer core is re-magnetized to opposite value of magnetization with exactly specified increment in each half period of the supply voltage. The increment of magnetization depends on type of transformer. The transformer starting method totally eliminates inrush current with minimal start up time (from 0,06 s for EI transformers and up to 3s for toroid transformers). This unique control proced- ure was patented. It has patent number CZ 296466. Magnetizing impulses are revised according to the primary voltage waveform. This principle ensures error-free operation with any trans- former secondary load.