Bus-hog problem in drives system-cause and remedy

Bharat Heavy Electricals has been supplying drives systems to a number of industries and power stations. Each of theses drives are controlled by an electronic rack containing a microprocessor card besides other cards. System hanging and bus hog problem in the processor card was reported in many drives during commissioning stage in a major steel plant where a number of drives systems had been supplied. The problem was studied in depth. Bus hog problem in the processor card arises when the devices addressed by the processor fail to respond within a specified time. The processor IC due to its excessive heat dissipation and associated noise generation was found to be the cause of the problem. In the processor boards of the drives systems where the above problem had been observed, the processor IC was changed from the existing NMOS version to a CMOS version as a CMOS processor IC dissipates less power during operation and generates less noise. After replacing the processor IC, drives systems have been functioning smoothly for 18 months and no hang up and bus hog problems were reported