As to continuous operating centrifuges, the following items should be taken into consideration in order to make the motors to run economically and reasonably:
1. Take the maximum power consumption of a centrifuge as a reference when selecting a motor, but not totally consider according the maximum power. Short time partial overload of a motor can be tolerated and its "overload ratio" (The percentage of overload part exceeding the rated power in the rated value) is determined by the percentage of overload time in a operation cycle. If the time percentage is low, the overload ratio of a motor can be relatively high; conversely, the overload ratio should be limited a little low, commonly around 20%~50%.
2. According to the startup of a centrifuge, from the performance of a motor, it's better to choose a special motor which has large starting torque, such as a slip ring motor or wound rotor motor, but as its high price, more than 40% higher than three phase (squirrel cage type) induction motor, therefore, this method is not normally used.
3. Still choose cheap and common three phase squirrel cage type induction motor and at the same time take measures to solve overload problem when the centrifuge is starting, say adopt the centrifugal friction clutch or hydraulic coupling, the latter the performance is better and more appropriate for explosion-proof field. The centrifugal friction clutch drives the pulley by mechanical friction plate friction, hydraulic coupling impulses turbine by liquid to drive the drum. Their functions can both make the centrifuge to start slowly which means longer starting time, avoid unreasonable selection of motors with much too large power; meanwhile as the starting is steady, the starting torque is too large and too much motor overload can be prevented. When the overload of centrifuge is very large beyond the bearing of motors, the friction plate and inner wall of pulley automatic sliding, or pump wheel and turbine liquid automatic slippage, so as to protect the motor effectively.