Ngo-1895, i-German Overtone yakhiqiza owokuqala emhlabeniI-DC drill kagesi. Igobolondo lenziwe ngensimbi ekhonjiwe futhi lingabhoboza izimbobo ezingu-4mm epuleti lensimbi. Kamuva, kwavela umshini wokubhoboza ugesi wezigaba ezintathu (50Hz), kodwa isivinini semoto sihlulekile ukudlula ku-3000r/min. Ngo-1914, kwavela amathuluzi kagesi aqhutshwa yizinjini zesigaba esisodwa, futhi isivinini semoto safinyelela ngaphezu kuka-10000r/min. Ngo-1927, kwavela ithuluzi likagesi eliphakathi nendawo elinemvamisa yokunikezwa kwamandla ka-150 kuya ku-200 Hz. Ayinayo nje inzuzo yesivinini esikhulu se-single-phase series motor, kodwa futhi inezinzuzo ze-motor frequency power frequency motor elula futhi enokwethenjelwa. Nokho, idinga ukuhlinzekwa nge-intermediate frequency current. , Ukusetshenziswa kukhawulelwe.