The role of the current transformer is used to measure the larger current

Current transformer is a kind of current commutation device,symbols for CT.Its role is to put the large current into a small current,supply measuring instrument and relay the current chart,indirect measurement by large wholesalemotor.blogspot.com current.But also can isolate high voltage,to ensure the safety of staff and secondary equipment.Current transformer secondary side current is 5 Why can't a current transformer secondary side circuit? Current transformer secondary side is not allowed to open operation.In the current transformer secondary coil on the instrument coil impedance is small,the equivalent of running in the secondary coil short- circuit condition.Transformer secondary coil terminal voltage on only a few volts.Of the magnetic flux in core is motor vehicle very small.Although primary coil magnetomotive force can reach hundreds or thousands of Ann ampere-turns or larger.But most were established by short circuit secondary coil demagnetization magnetomotive force offset,only a small fraction of excitation magnetomotive force as the core to establish a magnetic flux in the core.

If in running the diesel generating secondary coil disconnection,vice side current is equal to zero,then the demagnetization effect of magnetomotive force disappears,and the original edge of magnetomotive force is constant,the original edge measured current all become excitation current,this will make the iron core of sharp,magnetic flux core severe fever that burn out the coil insulation,or make the high side of short circuit.Other secondary coil open out the high voltage is induced,it is very dangerous for instrument and operators so current transformer secondary side is not allowed to disconnect. Why can't a voltage transformer secondary side short circuit? If the short circuit in the operation of the secondary 220v ac electric motors side of voltage transformer,secondary coil impedance decrease greatly,can appear a lot of short circuit current,make the secondary coil burned due to severe fever.So in the operation of the transformer are not allowed to short circuit.General voltage transformer secondary side with a fuse.Only transformer of 35 kv and below,on the high side have a fuse when transformer short-circuit the purpose is to put it cut off from the high voltage circuit

The rotation of the single phase ac motor principle

Only a single phase ac motor winding, is squirrel cage rotor. When a single-phase sinusoidal current in the stator winding, the motor can produce an alternating magnetic field, the magnetic field strength and direction interplanting sine law of change at any time, but is fixed on the spatial orientation, say again so the magnetic field is alternation pulse magnetic field. This alternation pulse magnetic field can be decomposed into two at the same speed and direction of rotation are instead of a rotating magnetic field, when the rotor static, the two rotating magnetic field generated in the rotor torque of two equal and opposite, making synthetic torque is zero, so the motor can't rotate. When we use the motor rotates in the direction of a force (clockwise), then the rotation of the rotor and clockwise direction magnetic field between the cutting lines of magnetic force movement decreases; The rotation of the rotor and counterclockwise direction magnetic field cutting electric motor 12v 500w lines of magnetic force between the movement. 

This balance is broken, the total electromagnetic torque generated by the rotor will no longer generator stator be zero, rotor spun along the driving direction. To make single-phase electric function automatically spin, we can add a starter in the stator winding, starting with the main windings in space by 90 degrees, starting winding to concatenate a suitable capacitance, makes differ with approximation in the phase of the primary winding current 90 degrees, the so-called split-phase principle. These two differ 90 degrees of electricity flow in time into the two differ 90 degrees of winding on the space, will be produced in the space (two-phase) rotating magnetic field, as shown in figure 2. Under the effect of the rotating magnetic field, the rotor can be automatic starting, after starting, to www.facebook.com/dongfeng.motor speed up certain, with the aid of an installed on the rotor of the centrifugal switch or other automatic control device will start winding disconnect, the only main winding work in normal working conditions. Therefore, starting winding can make short work. 

But there are a lot of time, starting winding is not broken, we call this kind of motor capacitor, single-phase motor to change this kind of motor, can be achieved by changing the position of the capacitor is concatenated. In single phase motor, the rotating magnetic field generated another method called shield electrode method, also known as single phase mask pole type motor. This made salient pole motor stator, which has two kinds of the poles and quadrupole. Each pole in a third - quarter pole face open place with full of small tank, as shown in figure 3, the magnetic pole is divided into two parts, on the small part of the suit on a short circuit copper ring, like pole to cover up this part, so called cover pole type motor. Single-phase winding set in the entire history of the magnetic poles, each pole of the coil is connected in series, the connection must make its polarity, in turn, according to the N, S, N, S arrangement. When the stator winding current in the magnetic main flux, according to lenz's law, which through the short circuit copper ring main magnetic flux in the copper ring produces a 90 degrees on the phase lag of the induced current, flux on single phase asynchronous motor the phase of the current and lag behind the main magnetic flux, its role and the capacitor motor starting winding, motor rotation to produce a rotating magnetic field.

Variable frequency speed control system

At present, the domestic research in variable frequency speed regulation system is www.dongfeng-motor.com very active, but also is not very ideal in terms of industrialization, most of the market is still dominated by foreign companies. Therefore, in order to speed up the development of variable frequency speed regulation system of our country, the needs of the international development trend of variable frequency speed regulation technology and the domestic market demand have a comprehensive understanding. The energy industry as the foundation of the national economy, for the development of society, economy and the improvement of people's living standard is very important. In the rapid growth of economic environment, China's energy industry faced with dual pressure of economic wholesalemotor.blogspot.com growth and environmental protection. The data show that, under the influence of capital, technology, energy prices, China's energy efficiency is much lower than the developed countries. Energy-intensive products of China in the 90 s energy is generally higher than in developed countries 12% to 55%, more than 90% of the energy in the mining, processing and transformation, in the course of storage and transportation and terminal diesel generators prices loss and waste.

 If the energy consumption per unit GNP (tons of standard coal/thousand dollars) country (mid - 90 - s), China respectively is Switzerland, Italy, Japan, France, Germany, Britain, the United States, Canada, 14.4 times, 11.3 times, 10.6 times, 8.8 times, 8.3 times, 7.2 times, 4.6 times and 4.2 times. In 1995, China's coal-fired power plant coal consumption of 412 grams of standard coal/kWh, 1.27 times that of the international advanced level. Therefore, the effective use of energy in our country is very urgent. As one of the large energy consumption of the motor in the aspect of energy saving is a potential can be dug. Total installed capacity of 400 million kilowatts of electric motor in our country, 600 billion KWH, electricity consumption accounted for about 80% of the industrial electricity consumption. In all kinds of used motor, more than 80% for small and medium asynchronous motor motor lamination under 0.55 220 kw. Overall equipment level in motor system in China is equivalent to the level of developed countries' 50 s. Therefore, 15 plans in the country, the motor system energy saving investment up to 50 billion yuan, so the variable frequency speed regulation system in our country will have a huge market demand. The current global economic development, there are two significant interwoven lines: energy and the environment. Energy of tension is not only restricted the considerable economic growth in developing countries, also brought quite a big problem for many developed countries. Where energy concentration also tend to be the focus of the world's hot spots. And the development and utilization of energy and protecting the environment has a significant impact. Global warming, acid rain, and a series of environmental disasters are related to the development and utilization of energy.