| Abstract |
If a microcomputer is employed to provide control signal processing in three-phase drives, than it is in the interest of reliability, that the pulse width modulation is likewise performed completely digitally. The rapid development of gate arrays provides a cost-effective means of realizing the digital pulse width modulator in hardware, as a peripheral circuit to the microcomputer. The modulator circuit, discribed in the following report functions completely digitally and thus offers favourable prerequisites for a gate array implementation. The maximum operating frequency is 20 MHz. This allows a high level of pulse pattern quantisation even for high converter frequencies. The harmonic oscillation components of the armature currents are effected by the ratio of the motor frequency to the sampling frequency of the microcomputer and by the way in which the microcomputer and the pulse width modulator are coupled. In order to achieve digital signal processing as far as possible, a poorly digital circuit for interlocking the converter bridge arms is also given. The interlock circuit is also capable of integration on a gate array. The design of the interlock circuit and the pulse width modulator as customized digital circuits allows the circuit outlay to be considerably reduced by comparison with conventional realizations. At the same time, enhanced reliability and easy installation can be anticipated. |
