Low voltage reactive power compensation of ore furnace
The stable operation of low voltage reactive power compensation of
ore furnace must solve seven characteristic questions
High frequency electrical characteristics: Transformer excitation and unbalanced loads will produce harmonic 3 times but only flow between the busbar (a triangle connection method) and does not react to a side; at the same time arc smelting will generate harmonic five times. Therefore install the reactive power compensation in the secondary side, equipped with the iron core reactor with the reactance rate of not less than 12% and 5.67% to suppress and partially absorb the 3 and 5 harmonic. It has a decisive impact on the quality.
Capacitive electrical characteristics: the relevant provisions of the state on the capacitive load: that is, the load capacity of the capacitive load carrier fluid must be 1.3 ~ 2.5 times of the rated current. The operating current of the low voltage reactive power compensation of a unit is generally more than 2000 amps, so must reduce the equipment heat by increase the carrier fluid loading cross section to increase the operation stability of the equipment.
Surge electrical characteristics: in the switching, the capacitive load will produce surge current higher than the inductive load. If the main circuit has no current limiting reactor, the current surge can up to 350 times for serious situation
Strong electrical interference characteristics: since the smelting electric arc current reaches tens of thousands or even hundreds of amperes. The scene will generate a strong alternating magnetic field. It will make the closed magnetic circuit produce eddy current effect. It will have an influence on the trigger signal of the electronic switch and leads to wrong conduction.
Physical characteristics of vibration: due to the reaction force of arc smelting and electromagnetic effects, the site has been in vibration. For operating low voltage reactive power compensation with low voltage, large current, vibration will have effect on fastening degree of the carrier fluid connection. If we do not take measures, the vibration will induce loose connections of high current and arc burning.
High temperature physical characteristics: the arc radiation, the furnace body and smoke cover heat radiation will cause the site environment temperature in summer will be as high as over 40t; at the same time low-voltage reactive power compensation equipment device itself will heat in its operation, double stack. If you don’t reduce the installation environment temperature and the operating temperature of the device, the lifetime of the capacitor will be greatly reduced.
Physical characteristics of dust: some fine dust produced by smelting floats and deposits in the field, which will have effect on, especially for the switching components, the components. Therefore the low voltage reactive power compensation should use contactless or vacuum contactor as the switching components.
The judgment of whether to install a certain reactance rate reactor is based on: whether the harmonic source load is greater than 20% of the total capacity not the harmonic content is beyond the standard!
Although reduce the rated current of the carrier fluid can reduce costs, its hazards can not be ignored.
So most of the equipment is not equipped with a certain reactance rate reactor, and its switching components can only use the way of zero switching. If vacuum cast is used, it will produce a vacuum arc welding; it is seemingly advanced, but in reality it is a helpless move.
This is why the thyristor or silicon control is used as switching components often burned. Of course it is also because of too large (IV drop)of silicon single crystal of power consumption of the nodes.
A lot of ablation or fire at the connection of the carrier fluid is caused because vibration causes loose bolts. It is seemingly small, actually has strong destroy. So we must use the anti loose design at the connection.
The glass (failure) temperature of the capacitor film is 80C. Therefore, it is necessary to adopt comprehensive measures to reduce the working temperature and environmental temperature of the capacitor. In addition to install the reactor with a suitable reactance rate, to enlarge the fluid section and select the high quality components, ventilation is also a necessary means.
Switching components only use vacuum or contactless switch; in case of the use of contactless switch, the cooling mode only uses water cooling. If wind cooling is used, dust will cover on the surface of the radiator, so the heat dissipation effect is decreased, which eventually leading to the thyristor or silicon control burning.
The characteristics of Low voltage reactive power compensation
|Double isolation circuit|
GG grade fuse protection
Mechanical self holding vacuum switching and counting
Automatic, manual, overhaul three state control
Grounding protection and fault treatment of single capacitor
Pure dry air filled silver zinc peritoneal capacitor
The temperature rise of the capacitor less than 10K
14%， 7% low noise iron core reactor (class F insulation)
Operating over voltage protection
Fluid amplification treatment
Magnetic isolation frame
Fastening bolt anti loose design
Automatic control of over pressure, over temperature
Automatic cycle switching control
Self discharging time protection control
Automatic control of equipment operating temperature