The harm of chemical pump motor three-phase voltage imbalance and resolve judgment method

In what is now the industrial production, the use of the chemical water pump a lot, as the user to use the convenient form of electricity, chemical water pump driven by motor is running normally, commonly used in industrial chemical pump motor three-phase voltage 380 v, so in the process of using unbalanced three-phase voltage instability how to judge? And what causes harm, how should solve? Three-phase voltage imbalance caused by a variety of reasons, such as: single phase grounding, wire resonance, etc. , we only to distinguish correctly, can quickly handle. A, 1, harm and influence of unbalanced three-phase power equipment: the influence of the occurrence of three-phase voltage imbalance will lead to reach several times the current imbalance. Of induction motor inverse torque increase, so that the temperature rise of the motor, efficiency, increase energy consumption, vibration, output lose money, etc. Each phase of the imbalance will lead to shorten the service life and electrical equipment to accelerate equipment parts replacement frequency, increase the cost of equipment maintenance. Circuit breaker allows current allowance to reduce, when the load changes or alternate prone to overload, short circuit phenomenon. Neutral line into the unbalance current is too large, in the lead to enlargement of neutral line. 2, the harm of transformer: in production, living power, three-phase unbalanced load, the asymmetric operation of the transformer. The transformer loss increase, Including no-load loss and load loss) 。 According to the relevant provisions of the transformer operating procedures in the running transformer neutral current shall not exceed 25% of the rated current on the low voltage side of transformer. In addition, the three-phase unbalanced load operation will cause the zero sequence current transformer is too large, local higher temperature of the metal, even lead to the transformer burned. 3, the line loss: the influence of three phase four wire connection way, the balanced three-phase load line loss small; When a heavy load, two phase under the condition of light load line loss increment is small; When a heavy load, the load is light, and the third phase of the load for the average load under the condition of line loss increment; When a load is light, two phase under the condition of heavy load line loss increment. When the three-phase unbalanced load, regardless of the load distribution, the greater the current imbalance, line loss increment. Second, the three phase unbalanced fault causes; 1, a ground fault when the circuit disconnection and single phase grounding, is caused by three-phase voltage imbalance, but after the grounding voltage values are not changed. Single-phase grounding into metallicity and non-metal earthing two kinds. Grounding metallicity, the fault phase voltage to zero or near zero, the fault phase voltage increases 1. 732 times, and the constant; Non-metallic grounding, grounding phase voltage is not zero but is reduced to a certain value, the other two phase rise less than 1. 732 times. 2, bolt break but not grounding fault if a photograph, or circuit breaker, isolating switch is not connected to a phase, voltage transformer blown fuse are caused by asymmetric three-phase parameters. On a break when a phase line voltage level, a voltage level of performance for three phase voltage is lower, compared to one of the low, but both high voltage value is close to than the other two. Line break at the corresponding level, disconnect phase voltage is zero, no break line phase voltage is still the phase voltage. 3, resonance with the rapid development of industry, plenty of non-linear power load increases, the certain load harmonic generation, not only has caused the power supply voltage fluctuation and flicker, and even cause unbalanced three-phase voltage. Is a kind of fundamental frequency resonance, characteristics of single-phase grounding, similar to the one phase voltage is reduced, the other two phase voltage rise, to find the cause of the problem is not easy to find fault point, users can now special inspection, if not for grounding, is likely to be caused by resonance. The other is a points or high frequency resonant frequency resonant J&T water pump, is characterized by three-phase voltage rise at the same time. Three, three-phase imbalance harm and solution of A. Unbalanced three-phase voltage or current factors such as the main hazards in the condition of asymmetric 1, rotating motor, the rotor causes additional loss and heat, causing the motor as a whole or partial, in addition to reverse magnetic field to produce additional moment will cause a vibration motor. For generator, also can form a series of higher harmonic in the stator. 2, for generator, transformer, when three phase unbalanced load, such as control large current rating, the remaining two phase cannot be full, and equipment utilization rate of decline, whereas if you want to maintain the rated capacity, load will cause the larger of the overload, but also can appear unbalanced magnetic circuit waveform distortion, additional loss of equipments, etc. 3, caused by the negative sequence component to start the components of a variety of protection misoperation, direct threat to power grid operation. 4, unbalanced voltage cause a non characteristic harmonic silicon rectifier equipment. B。 Caused by asymmetric load of power grid three-phase voltage imbalance can take solution 1, disperses the asymmetry load in different power supply, to reduce the concentration connection caused by unbalanced degree exceeds bid badly. 2, using cross in equal way to asymmetric load distribution to each phase, try to make it balance. 3, increase the load of the access point short circuit capacity, such as change the network or to improve the voltage level to enhance the capacity of system under unbalanced load.
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