Research On Ultra-high-slip Motors For Pumping Unit Drive

Determination of the most efficient electric motor driver for cyclic loading such as beam pumps has been a tedious problem. The ultra-high-slip motor (U.H.S.M) is one of the most popular resolve.U.H.S.M used to drive beam pumping unit has been manufactured in lots of oil-fields because that U.H.S.M has good start-up and soft characteristics, suitable for driving beam pumping units which are started up under loading condition and show a cyclical variation of polished rod load. According to kinetic energy balance, it may reduce the capacity of motor and electrical installation get smoother operation and reduce the peak of net torque. But there is a problem of how to make a proper selection of the motor slip rate according to the oil well working parameters. Different performance curves show that various beam pumping units driven by U.H.S.M have better working condition.Optimum slip rate can be determined so that we can decrease electric energy consumption, raise working efficiency and increase oil output, lengthen the survive life of the equipment and get good economic benefits. In order to improve the current situation of low efficiency and energy wasting of pumping units in the oil-fields, in this paper we are using optimization methods to find the best motor slip for U.H.S.M and planning to complete the electromagnetic design of U.H.S.M. The principle and method of selecting the optimum slip rate of U.H.S.M are presented and the influencing factors are discussed. Using this optimum method, the optimum slip rate of revolution is calculated and accordingly the type of motor and torque can be determined.