Effects of Voltage Quality on Induction Motors’ Efficient Energy Usage

Abstract

Unbalance voltage can occur due to the presence of larger single-phase consumers or asymmetrical capacitor banks with damage or capacitors that are switched off due to the fuse burning only in one phase. Nowadays, the presence of higher harmonics in the supply voltage is ever more frequent due to the growth of consumers who are supplied through the rectifiers and inverters: regulated actuators, electrothermical consumers and consumers alike. The effect of a variation in supply voltage, wave-form or frequency on the motor's efficiency and power factor characteristics depends on the individual motor design. Typical variations of current, speed, power factor and efficiency with voltage for constant output power are given in Fink (1983). The usual characteristics of induction motors within the ±10% voltage band (Un±10%) are well known. These are included in corresponding table for typical 30-100 kW, 1500 or 1800 1/min motors (Linders, 1972; Fink, 1983), but the effect of saturation has been largely neglected in these tables. However, it is the author's intent to show a correlation between motor characteristics and voltage level. This proposed has three parts: 1. Study of the effect of voltage magnitude on motor losses and motor reactive loads, 2. analysis of the effect of unbalanced voltages, and 3. analysis of the effect of non sinusoidal voltages to the efficient energy use. 2. Effect of voltage magnitude on motor power losses and motor reactive loads Voltage magnitude has a significant and different influence on motor loads and electric energy consumption, depending on types, nominal powers and load level (p=PPN) of motors. Data found in classic references (Fink, 1983) are almost identical to data from older references (Linders, 1972;), although they are not accurate enough for motors made after 1970. The main reason for disagreement is higher values of no-load current and more significant dependency of core losses on voltage magnitude for newer motors (U or T shape of magnetization curve). Data for loads less than 50% are not available in Fink (1983) and Hamer et al. (1997), although more than half of motors operate in these load regimes.

Economic evaluation of induction motor based on motor’s nameplate data and initial cost

“…The corresponding state equations are in ( 2) and (3). Algebraic equation expressed the active energy losses in [kWh], that is; the total energy losses ∆E and respectively the no-load ∆ENLL and the on-load energy losses ∆ELL is as in (4).…”

“…Different approaches have been proposed to assess the technical and economic IMs' cost and design problems [1]. The amount of energy consumed by all motors to overall electric energy produced varies between 43% and 49% [2], while the IM consumes 96% [3]. Elzbieta and Leszek [4], introduced a statistical technique was used to estimate the motor's collective losses for various motor output powers were computed.…”

Assessing Energy Efficiency and Power Quality Impacts Due to High-Efficiency Motors Operating Under Nonideal Energy Supply

“…The presence of VU also results in unbalanced currents in the stator windings. Normally, the current unbalance is 6-10 times the voltage unbalance, which causes the winding to overheat [17], [39]. To better analyze this fact, see Figure 6 for an ungrounded wye connected motor.…”

Assessing Voltage Unbalance Conditions in IE2, IE3 and IE4 Classes Induction Motors

“…In relation to the temperature, the VU results in uneven increases in current, increasing joule losses and thus the operating temperature [32], [33], [35]- [37], [41], [42]. In [43], experimental results show that unbalance with under voltage results in the largest temperature increases.…”