Using a variable speed drive on a farm is one way of saving on a farm’s energy expenditure. Variable speed drives are crucial for certain farm machinery such as vacuum pumps. This is because this machinery operates at full speeds for maximum capacity loads, even though the maximum capacity may not be utilized. A vacuum pump for example will work at speeds calculated for largest anticipated demand. In reality this demand is utilized for only 1% of the pumps overall operations. This leads to a waste of energy and noise pollution.
Modern vacuum pumps that utilize variable speed drives are able to change pump capacity to meet the required needs. These drives are fixed to a motor and act as speed regulator. The energy efficiency of these drives allow for energy savings of 50% to 80%. The primary function of these pumps is to move milk from the cow to the storage tank and to flush the system with water and sanitizing agents for cooling. A conventional vacuum pump always operates at maximum capacity and uses a regulator to draw extra air into the system. A variable speed drive on the other hand will be able to match the amount of actual air in the system with pump speed. This is achieved by regulating the speed of the motor instead of trying to regulate the system vacuum level.
These drives can be used on lobe or blower vacuum pumps. This allows the system to achieve 100% efficiency in working. A variable speed drive is 50% more efficient than a normal drive. The savings incurred by using a variable speed drive will allow a person to recover the initial investment in one to four years.
Variable speed drives work with constant torque loads. This differs from a regular pump or fan which varies with the cube of speed. Instead these drives vary power in direct proportion with speed. A variable speed drive that is implemented in a dairy environment is considered to be as reliable as when a regular drive is used for the process.
The main components of a variable speed drive vacuum pump system are the three-phase electric motor, a variable frequency drive unit and a pressure transducer. In order to work efficiently, pumps should have air circulating around the unit to prevent overheating. A small hole can be made according to manufacturing specifications to allow more air to pass through it.
Variable Speed Drives have the added benefit of being quieter than a regular drive. Since variable speed drives slow the average speed of the pump to less than half the constant speed, it reduces the amount of wear and tear that the pump is otherwise subjected to. Pumps with variable speed drives do not require constant oil lubrication of the pump cavity and thus decreases the number of oil related pollutants that contaminate the soil near the pumps exhaust.