Abstract: In order to carry out commercial synchronous exchange for disconnecting an induction motor from its driving power supply and connecting it to a variable frequency power supply or commercial synchronous switching for disconnecting the induction motor from the variable frequency power supply and connecting it to a commercial power supply without any accompanying adverse shock, an induction-motor vector control technique is utilized and furthermore, a phase-locked loop (PLL) is formed to detect the difference in phase between the phase of the output voltage from the variable frequency power supply or the magnetic flux phase of the induction motor on the one hand, and the phase of the voltage of the power supply on the other, so that the difference in phase thus detected can be maintained at a predetermined value.

Abstract: A monolithic integrated circuit generates a programmable time delay under control of a digital work. The delay is generated by comparing a ramp signal to a threshold determined by the value of the digital word and appears as a time difference between a trigger pulse and a pulse generated when the value of the ramp voltage equals the value of the threshold voltage. The ramp voltage is generated by a simple resistance/capacitance charging circuit whose time constant can be adjusted by the user. The threshold voltage is set by a digital-to-analog converter (DAC) and resistor circuit which converts the digital control word into a variable voltage. In order to stabilize the device against changes in temperature and power supply variations, a voltage coupling circuit forces the threshold voltage to track changes in the ramp voltage caused by temperature and power supply variations.