Investigations on a micro linear stepping motor supplied by a DC-DC converter

This paper reports on a micro linear stepping motor which is supplied by a dc-dc converter. The micro linear motor is built up by using micro fabrication techniques like sputtering, UV depth lithography and electroplating [1, 2, 3]. In order to adjust the stator current, an adapted drive has been developed. Due to the very small inductances of the motor coils, the chosen dc-dc converter works with a switching frequency of more than 1 MHz. Nevertheless, the current is not constant at all, because the time constant of the stator winding is only 100 ns. The effects due to the harmonics of the voltage supply will be considered and analysed by using transient finite element method simulations. Therefore, a FEM model of the motor for transient analysis has been developed and the losses have been calculated. It could be shown that the additional motor losses due to eddy currents, skin effect and current displacement are negligible. But it has to be taken into account that the increase of the r.m.s. value of the current caused by the current ripples results in higher copper loss having a constant mean value of the current.