The transformer is S9-30/10. Phase A is equipped with a set of equipment. The measured long-term operating current is 15-17A. Phase B and C currents are small, and they will not exceed 2A. The transformer low voltage \? line is 25 square aluminum core wire, the neutral point is well grounded, and the grounding resistance is 3Ω.
1, 3 line voltage is basically balanced, all in 385-390.
2. The phase A voltage is low, between 198V and 208V.
3, B phase, C phase voltage is high, between 225V ~ 230.
4, A phase voltage and phase B phase voltage difference is basically no less than 20V, so I dare not use the method of increasing the voltage.
Phase A load is not adjustable because it is a complete set of equipment. What is the solution? As far as possible, increase the voltage of phase A and it can be more than 215V.
You did not provide the specifications of this transformer. I checked it and found the next table, which is about 30 KVA. Theoretically, the current should be about 60 amps at 220 V phase voltage, and your load current does not exceed the rated current. The grounding resistance of 3 ohms is also less than the required 4 ohms. Your customer's request can only be connected to one phase. Unbalanced loads can of course cause voltage imbalances.
One, probably analysis
Although the neutral point of the transformer is grounded, the potential of the neutral point is fixed, but the neutral voltage of the unbalanced transformer is not "dead fixed"! There are three reasons. One is that although the neutral point of the transformer is grounded, the grounding resistance is not zero. The standard requirement is less than 4 ohms. It is this 4 ohm. When the load is unbalanced, it will cause the three-phase voltage of the transformer to have Small offset.
The second is that although the resistance of the three-phase line is very small, due to the existence of single-phase load, the length, cross-section, and load size of the three-phase line are also inconsistent. Therefore, if the measurement is taken at the user, the neutral point must not be zero. The situation, that is, the three-phase voltage deviation. The third is that when the ground wire of the transformer is disconnected, the neutral point will be shifted due to unbalanced three-phase load, resulting in inconsistency of the three-phase voltage, and this inconsistency will, in turn, increase the unbalance of the three-phase load.
= (17-2) ÷ 17 × 100% = 88.24% In a three-phase four-wire transformer, the neutral current caused by the unbalanced current must not exceed 25% of the rated current of the low voltage winding, and you obviously exceed it, of course. To be solved.
Gantry crane bridge crane is a kind of deformation, also called gantry crane. Mainly used in Outdoor Yard, loading and unloading of goods, the bulk of the field. Its metal structure as a door shaped frame, bearing girder installation of two legs can be directly in the ground track walk, at both ends of a main beam can with cantilever beam. Gantry crane has the space utilization rate is high, and large working range, adapt to wide, general characteristics, widely used in port yard.
Photo of our Gantry:
Formal classification
Gantry crane can be according to the structure of the door frame, according to the main beam form, according to the main beam structure, according to the use of the form of classification.
Door frame structure
Door type crane and cantilever gantry crane
Portal crane
1. the whole gantry crane: the main beam without suspension, the car in the main span of the;
2. half gantry crane: the legs are high or low, can be used in accordance with the requirements of the use of the site.
Cantilever gantry crane
1. double cantilever gantry crane: the most common form of structure, the structure of the force and the effective use of the site area are reasonable.
2. single cantilever gantry crane: the structure of the form is often due to the restrictions of the site was chosen.
Main beam form
1. single girder
Single girder gantry crane has the advantages of simple structure, convenient manufacture and installation, its quality is small, the partial rail box frame structure. Compared with the double girder gantry crane, the overall stiffness is weaker. Therefore, when the weight is Q = 50t, S = 35m span, can use this form. L type and C type two forms of single girder gantry crane legs. L type of manufacture and installation is convenient, the situation is good, its own quality is small, however, the lifting of cargo through the supporting legs of the space is relatively small number of. The C shaped support legs are bent or bent, and the purpose is to have a larger transverse space so as to enable the goods to pass through the supporting legs.
2. double girder
Strong ability of bearing double girder gantry crane, span is big, the overall stability is good, many varieties, but its quality with the same play weight of single girder gantry crane compared to larger, the construction cost is also high. According to the different structure of the main beam, it can be divided into two types of box girder and truss. Generally use box structure. [1]
Main beam structure
1. truss beam
Structure using I-steel welded together, has the advantages of low cost, light weight, good wind resistance. However, due to the defects of the welding point and the truss, the truss beam has large deflection, small rigidity, low reliability, and so on. Applicable to the safety requirements of the lower, the smaller the weight of the site.
2. Box Girder
The use of welded steel box type structure, has the advantages of high safety, rigidity etc.. Generally used for large tonnage and large tonnage gantry crane. Such as the MGhz1200, the weight of 1200 tons, is the largest gantry crane, main girder with box girder structure. At the same time, the box beam has the disadvantages of high cost, great self important, poor wind resistance and so on.
3. cellular beam
Generally refers to the isosceles triangle honeycomb beam, the beam end is a triangle, on both sides of the diagonal with honeycomb holes, the upper part and the lower part of a chord. The cellular beam absorbs the characteristics of the truss beam and box girder, which has larger stiffness, smaller deflection and higher reliability than the truss beam. But because of the use of steel plate welding, the weight and cost ratio of truss beam Shaogao. Suitable for use in frequent or high weight field or beam field. Because of this type of beam type for patent products, so manufacturers less.
Use form
1. ordinary Longmen crane
This kind of crane adopts box type and truss structure, the most widely used. Can carry a variety of pieces of goods and bulk materials, the weight of 100 tons, the span of 4 to 39 meters. With ordinary high-level gantry crane Grab. General gantry crane is mainly refers to the hook, grab, electromagnetic, gourd gantry crane, which also includes semi gantry crane.
2. hydropower station Longmen crane
Mainly used for lifting and opening and closing the gate, but also to carry out the installation work. Up from 80 to 500 tons, the span is smaller, is 8 to 16 meters; the lifting speed is low, for 1 ~ 5 m / min. Although this crane is not a regular crane, but once the use of the work is very heavy, so to increase the level of work properly.
3. shipbuilding Longmen crane
Ship to berth assembly, standing with two lifting trolley: A has two main hook, running on a bridge on the flange of the track on; and another has a main hook and a pair of hook, run on the flange of the rail of the bridge to turn and lifting of large hull block. Lifting weight is generally 100 to 1500 tons; span of 185 meters; lifting speed of 2 ~ 15 m / min, and 0.1 to 0.5 m / min of the micro motion speed.
4. container crane in Longmen
For container terminals. Trailer bridge to quay container carrying containers unloaded from the ship
Transported to the yard or rear, carried away by the container gantry crane duima up or direct loading, accelerate the turnover of the bridge or other crane container carrying. Can be stacked high 3 to 4 layers, 6 rows of the container yard, the general use of the tire type, but also useful. Compared with the container truck, Longmen crane span and the height of both sides of the gantry are larger. In order to meet the need of the transportation of the port and wharf, the working level of this kind of crane is higher. From the lifting speed is 8 ~ 10 m / points; span across the container as needed to determine the number of rows, up to a maximum of 60 meters corresponding to 20 feet, 30 feet, 40 feet container weight were approximately 20 tons, 25 tons and 30 tons.
Gantry
Boat Gantry,Lifting Gantry,Overhead Gantry,Aluminum Gantry
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