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 yejubane eliphezulu le-motor yesigaba esisodwa, kodwa futhi inezinzuzo ze-motor frequency power frequency motor elula futhi enokwethenjelwa.Nokho, idinga ukuhlinzekwa nge-intermediate frequency current., Ukusetshenziswa kukhawulelwe.