Analytical assessment of torque and stator currents of an induction motor due to voltage sags

Voltage sag is a frequently encountered phenomenon in a power system to which many three phase induction motors are directly connected. This paper presents a simple analytical method for calculation of net electro-magnetic torque and stator currents of an induction motor subjected to symmetrical as well as unsymmetrical sags in supply voltage. This work presents an innovative path to compute net electro-magnetic torque and increase in stator currents for all seven types of sags using the well-known symmetrical component theory. Such a simple method and expressions used in this paper are not reported in the literature reviewed so far. The computation is further extended for different load conditions while varying the symmetrical sag magnitude. The simplicity of analytical assessment of loading effect on electro-magnetic torque from no-load to full-load condition for all sag types is presented. The outcome of the study was verified by imitating the environments for various types of sag in MATLAB/Simulink. The observations are that the average output torque of a motor decreases and ripple in power increases during unsymmetrical sags

Water requirements in growth stages and effects of deficit irrigation on fruit productivity of drip irrigated Nagpur mandarin (Citrus reticulata)

The field experiment on irrigation scheduling based on pan evaporation replenishment through drip irrigation system was conducted to find out the water requirements in critical growth stages of 8-10 years old bearing Nagpur mandarin (Citrus reticulata Blanco) during 2009-2012 at NRC for Citrus, Nagpur. In this trial five levels of pan evaporation based irrigation schedules with respect to critical water requirement, plant growth, soil and leaf nutrient status, yield and fruit quality was investigated. The irrigations were scheduled on percent of pan evaporation replenishment (ER) in various stages of growth and fruit development. The different stages considered in this study are: Stage-I (Jan-Feb), Stage-II (Mar-Apr), Stage-III (May-Jun), Stage-IV (Jul-Aug), Stage-V (Sep-Oct) and StageIV (Nov-Dec).The treatments were irrigation schedule with 30% ER in stage-I, III, V and 40% ER in stages II, IV and VI (T1), irrigation schedule with 40% ER in stage-I, III, V and 60% ER in stages II, IV and VI (T2), irrigation schedule with 60% ER in stage-I, III, V and 80% ER in stages II, IV and VI (T3), irrigation schedule with 80% ER in stage-I to VI (T4) and irrigation schedule with 30% ER in stage-I to VI (T5) with three replications in Randomized Block Design. The study indicated that the irrigation water requirement of drip irrigated Nagpur mandarin scheduled at 80% ER in stages I to VI ranged from 35.3 to 188.1 litres during 2009-2012. The growth of plant height (4.73 m) and stock girth (66.37 cm) was more in irrigation scheduled at 80% ER in stages I to VI. There is a significant in increase in canopy volume (68.97 m3) in irrigation scheduled at 80% ER in stages I to VI. The average fruit yield recorded was 16.09 tonnes per ha. in irrigation scheduled 80% ER in stages I to VI. The average fruit weight, Total Soluble Solids, juice percentage was high in irrigation at 80% ER in stages I to VI in comparison with other irrigation schedules. The study revealed that the irrigation scheduling at critical water need affect the plant growth, yield and fruit quality of Nagpur mandarin with drip irrigation scheduling less than 80% ER in all stage

Interactive effect of irrigation schedules and fertigation levels on fruit yield, quality and plant nutrition of Nagpur mandarin (Citrus reticulata)

Water and nutrient-useefficiency, both are considered as pre-requisites for sustained citrus productivity. The interactive effect of irrigation and fertigation levels on growth, yield and quality of 11-year-old Nagpur mandarin (Citrus reticulata Blanco) was studied through a field experiment during 2010-13 at ICAR-Central Citrus Research Institute (Formerly NRCC), Nagpur under AICRP Fruits. The experiment was laid out in split-plot design with nine treatment combinations, comprising three irrigation levels (70 %, 80 % and 90 % of daily evaporation replenishment) and three fertigation levels (60 %, 70 % and 80 % RDF based NPK doses) replicated six times. Canopy volume (74.9 m3) and fruit yield (19.2 tonnes/ha) were observed maximum with the drip irrigation scheduled at 80 % ER combined with 80 % RDF fertigation. The fruit quality parameters, such as fruit weight (129.2 g), juice percentage (45.05 %), TSS (10.27o Brix) and lowest acidity (0.81) were observed favorable with irrigation at 80% and fertigation at 80% RDF, in addition to maximum nutrient concentration in index leaves ( 2.38 % N, 0.12 % P and 1.50 % K) duly supported by changes in available pool of nutrients in soil (123.8 mg/kg N, 14.8 mg/kg P2O5 and 261.2 mg/kg K2O). Interestingly yield efficiency computed as fruit yield per unit canopy volume was also observed maximum (0.26) with treatment carrying irrigation at 80% ER and fertigation with 80% RDF. The sustained productivity of Nagpur mandarin can be achieved with irrigation scheduled at 80 % ER along with fertigation technology at 80 % RDF without any potential nutrient mining

Evaluation of in-situ Soil and Water Conservation Treatments on the Performance of Acid lime (Citrus aurantifolia Swingle) on Vertisols

Different in-situ soil and water conservation treatments consisting of continuous trenching, continuous bunding, staggered trenching between the rows and control (without any soil and water conservation treatment) were evaluated during 2003-04 in II years old acid lime orchard at Nagpur. All the conservation treatments were effective in checking loss of runoff, soil and nutrients, which resulted in a favourable response of the plants in terms of better growth, fruit yield and quality, compared to those under the control. The treatment, continuous trenching produced the best response conserving 38% runoff, 32.28% soil loss, 32.44%N, 27.67% P, and 28.95% K over control, besides 18% higher fruit yield