Automatic control technology for vacuum stability

In conventional vacuum milking system, vacuum pump/motor runs at full speed and load regardless of any change in the actual air flow used for milking cows or washing pipelines. Excessive vacuum pump capacity is admitted through a vacuum controller unit which is used to maintain milking vacuum stability. Considerable energy has been wasted by the conventional vacuum milking system on diary farms. It is estimated that up to 70 percent of electrical energy is wasted during milking and perhaps 50 percent during washing. There is a potential for reducing electrical energy used by vacuum pump/motor.; Energy can be saved and electrical demand can be reduced by regulating vacuum pump capacity according to air flow usage. In this thesis, two vacuum milking systems with variable speed pump have been developed and analyzed. The two systems are a vacuum milking system with adjustable speed drive plus volume reserve (Adjustable speed drive) and vacuum milking system with adjustable speed drive plus vacuum and volume reserve (ASD-dual vacuum milking system). The adjustable speed drive plus volume reserve can reduce the energy consumption to the minimum level, but the system could not maintain vacuum stability within the generally accepted limits. ASD-dual vacuum milking system can both maintain the milking vacuum stability within the limits and reduce energy usage. Experimental results show that vacuum stability in the ASD-dual vacuum milking system is better than both the conventional vacuum milking system and the vacuum milking system with adjustable speed drive plus volume reserve. The ASD-dual vacuum system can reduce energy consumption and demand by 60 percent during milking.; The economic measurements for the investment of the ASD-dual vacuum milking system are much better than the ASD plus volume reserve system. For the dairy farm used and assumptions made in this thesis, the payback period is about 3 years, the net present value of the investment ranges from {dollar}4679 to {dollar}7504 and the internal rate of return ranges from 33.3% to 37.4% for the ASD-dual vacuum milking system respectively.