Research of ways to improve the start of the asynchronous motor of an agricultural machine
Abstract
Agricultural machines, due to the peculiarities of technological processes, poor quality electricity in rural networks and unskilled personnel, have statistically more frequent emergency modes of operation, long and short-term overloads and more engine failures. Such modes are typical for asynchronous crusher motors, feed shredders, feed mixers, conveyors, centrifugal fans, manure harvesters, etc.
Electric motors are known for their very high efficiency compared to other drive mechanisms. The high value of the efficiency is true for established work in nominal modes, during the transient losses increase significantly. One of the most costly processes is acceleration: to reach the required motor speed, you must provide increased torque, which leads to an increase in current and, accordingly, a quadratic increase in electrical losses. This is especially important for drives operating in repeated short-term operation, ie with frequent stops and starts.
It is possible to improve the starting properties of the induction motor overloaded at the time of startup by changing the initial conditions for connecting the motor to the mains (initial phase of the supply voltage, angular position of the rotor). In this case, starting with maximum impact torque is ensured, which has a positive effect when starting engines with high starting torque.
The possibility of increasing the operational reliability of the drive of agricultural machines for over-loaded induction motors during their startup has been studied.
As a result of the conducted researches it was received: for definition of the maximum transient mo-ment of the induction motor the expression for definition of peaks of transient moment at startup. In order to eliminate the emergency overload mode when starting asynchronous motors, a method has been developed to protect the motor by generating a dynamic torque at startup. This is achieved by "cutting" the negative dynamic moments.
