Fabrication and Development of Signal Loss Recovery System for AC Drives

AC motors play a vital role in industrial and domestic applications. Due to different tasks of application, most of the industries need to have variable speeds of operation of AC motors using Variable Frequency Drives (VFDs). The operation of VFDs is controlled by control signals from reference signal generator. Here, it has to be noted that transfer of analog control signal to the electric drive, from reference signal generator (located at the control room) will takes place through control bus. Long distance control bus routing and bad operating environment leads to possible failure of signal transfer on control bus. Due to such failures, the drive ends up losing the control from operator. Present paper describes a protective device to control bus. The Signal Loss Recovery System for AC Drive is intended to feed the control signal to the Variable Frequency Drive (VFD) in case of failure in control signal transfer to VFD. The System contains „Analog to Digital and Digital to Analog Converters‟ and Fractional Signal selector switches with system Status Indicators. For the effective control of the whole system, a microcontroller is included. This paper describes the Fabrication and Development of one such Signal Loss Recovery System. The operation principles, control algorithm employed in this context and the interesting results obtained are presented in this paper. Keywords— Control signal, Reference signal generator, Variable Frequency Drive.