Исследование пуска электропривода насоса дождевальной установки с функцией ограничения потребляемой мощности

Abstract

INVESTIGATION OF ELECTRIC DRIVE START OF SPRINKLE MACHINE PUMP WITH FUNCTION OF LIMITATION OF POWER CONSUMPTION 

I. Golodnyi, A.V. Toropov

Introduction. Recently there has been an increasing use of sprinkle machines; powered by autonomous sources of electrical energy, in particular diesel generators. At the same time, one of the significant problems with the use of autonomous power sources in sprinkle machines is their limited power, in comparison with power transmission lines.

Analysis of recent researches and publications.

Almost all of the soft starters (SS) for induction motors in their functional have two types of ramp fuction:

- a function of a linear or parabolic increasing of output voltage;

- function of restriction of the stator current limit value.

Purpose – reducing of the starting current of sprinkle machine pump electric drive using the system "soft starter - asynchronous motor" using the function of linear ramp of the stator current.

The materials and methods of research.

Research of the transient processes in electric drive of a sprinkle machine pump with a smooth start were carried out using statements of  electric drive theory and static methods for processing the results of computer model investigations in the MatLab system.

The results of the research. The linear ramp function in soft starters with three regulated phases is implemented. The start of the electric motor with two regulated phases due to the presence of a constant component of the stator current at low speeds of the motor shaft, which leads to an additional braking of the motor, is practically not used. This, in turn, leads to stator current jumps and possible failure of power thyristors. To analyze the dynamic characteristics of electrical systems, the MATLAB package and its Simulink application are used. The start-up algorithm with the current limiting function in the following sequence is realized. In the created model of the electric drive, the signal from the stator current ramp is compared with the actual value of the stator current. If the current reference exceeds the actual value, the firing angle is reduced and the motor is accelerated. When the stator current exceeds the set value, the firing angle is fixed at its last value. The startup algorithm is repeated until the end of the specified acceleration process and then the peak current output is achieved.

Conclusions and perspectives

Using of softstarter allows to reduce starting current to the value less then 2,1I_N, so start-up procedure of sprinkle machine induction motor is carried out during 2,5 seconds without significant jumps and oscillations.

The actual value of the initial firing angle is recommended to be set at the level of 2 radians.

The maximum consumed total power during pump start-up does not exceed 1.7РN of the motor. Provided that the overload capacity of diesel generators is 150% to ensure a guaranteed start-up, it is sufficient to use an autonomous power source only a step higher, relative to the motor.