As the market size required for air separation plants growing, the distribution
Motor (mainly air compressor motor) capacity is also growing.
In order to reduce air separation plant operating conditions affect the process by the network capacity
Degrees, the motor starting method becomes particularly important.
Here's a variety of high-voltage soft starter to do an analysis and comparison, to the election
Select the appropriate soft-start approach to better meet the air separation plant hosts
Starting requirements.
Of the types and characteristics of a soft-start
Motor terminal voltage (or voltage and frequency) continuous slow increase
Canada, so that a smooth increase in motor speed until the rated speed operation,
Known as the soft-start motor. Soft-start can be divided into a class and no class 2
Class, the former regulation is sub-file, the latter adjustment is continuous.
The traditional soft-start are a class, such as satellite / angle transformation from soft -
Move, auto-transformer soft-start, soft-start, etc. reactor. Such effect
Dynamic way as a conventional type commonly used here does not describe.
Non-stage soft-start are: the liquid electrolyte resistance soft-limiting effect
Move, switch-mode transformer soft start, soft start and frequency soft magnetic effect
Moving, etc..
1.1 fluid resistance (heat change) soft-start
Resistance is a liquid formed by the electrolyte resistance, it is conductive to the
Quality is the ionic conductivity. Its resistance is proportional to the relative two electrode plates
Distance, inversely proportional to the conductivity of the electrolyte, electrode distance and conductivity
Rates are easy to control. Of the heat capacity of large liquid resistance. Because it has many
Highlight the advantages of liquid resistance soft starter in every industry that is widely
. Main advantages are:
(1) The resistance value can be no level control and resistance heat capacity, which
It is precisely the soft-start needed; in soft-start the process does not produce high
Harmonic.
(2) a very important advantage of the low-cost, cost-effective than the
High.
(3) Liquid Resistance Soft Starting device could be linked together in the motor winding turn
Sub-loop soft-start to achieve overload.
(4) As the manufacturing technology is relatively mature, fluid resistance of the soft starter
Be able to start the motor power range has been great development.
However, due to its structural characteristics, which have corresponding disadvantages:
(1) The large volume of liquid resistance box, which is rooted in a resistive current-limiting, reducing the
Small volume will cause the temperature to increase. After the electrolyte is usually a soft-start
There will be 10 ~ 30% of the temperature, so that poor reproducibility of soft starting.
(2) Liquid Resistance Soft Starting need to maintain liquid water in the tank need to be
Complement. Electrode plates in the long-term immersion in the electrolyte, the surface will be a
Set rust, the use of a longer time after the required surface treatment.
(3) Liquid Resistance Soft-start device is not suitable for easily placed in the ice
On-site.
Liquid Resistance Soft Starting Devices has long been used abroad. So far, in domestic
Is still running a lot of foreign liquid resistance soft start products, from the
Japan, Canada, Italy and other countries. Ex-factory date from the 20th century
60's to the 20th century, both 90 years. Domestic products production plant
Home many a high-profile in Xiangfan, Hubei DAY companies and big
Force companies Reinol several companies and companies in Shanghai.
In recent years, liquid resistance soft start in the air separation device has also been a large
Volume of applications, air separation Kaifeng, Hangzhou and Sichuan I oxygen and air in the 3200m3 / h to
15000m3 / h Air Separation Plant in applications where electrical power from the
2000kW to 8000kW. Chengde Steel Plant which opened in an empty set of
15000m3 / h air separation plant using liquid resistance soft start the motor power has been
Reach 8000kW, application of good results. Liquid resistance in other industries
Soft-start the applications are very broad. Currently with liquid resistance soft start motor
The maximum power reached 20000kW, this is the many other types of
The soft starter can not reach the value of the motor power.
1.2 Switching Transformer Type Soft Starter
Switching Transformer Type Soft-start electrical power through the use of PLC
Sub-device control switch transformer low voltage side, to control high-pressure side of the
Electrical parameters to complete the soft-start motor. With liquid resistance soft start phase
Ratio, its small size, compact structure, virtually maintenance-free, functional Qi
Full, menu is rich in repetitive starting, protect and thorough. Soft Start
Methods are: Voltage slope type and phase constant-current type. Switching Transformer
Soft-start single-line diagram shown in Figure 1, soft-start methods shown in Figure 2.
3kY ~】 0kV
U
200kW ~ 6000kW
Figure 1 Switching Transformer Type Soft-start-line diagram
T T
Figure 2 Voltage slope type and phase constant-current soft-start
Switching Transformer Type Soft Start Technical Features:
(1) light load soft start, the starting current is less than in the 2.5Ie.
The output voltage can be adjusted continuously from zero onwards, starting the process does not produce
Over-voltage.
(2) control of high precision, good repeatability. The unit energy consumption
Is small, self-temperature rise is small, you can start a row.
The soft-start product defects are:
(1) high prices too high, is the liquid resistance soft start of the three
~ 5 times.
(2) thyristor high frequency harmonics caused by more serious.
(3) wound rotor induction motor can not be used.
In these shortcomings, the high prices are the main constraints to development
Factor.
The product is a late start in China, but the development is very rapid, should be
With the prospect of very wide. The product of air separation equipment, has just opened
Beginning a few days ago in Kaifeng Air Separation Group, sets of Echeng Steel
2000Om / h of the first application of air separation equipment, using a drag III
Program, the electrical power, respectively lOOOkW, 400OkW and
1000OkW.
1.3 Magnetic soft-start
This soft-start value of the electrical resistance change is by controlling the DC-Li
Magnetic currents, changing the iron core saturation to achieve, so called magnetron
Soft-start. Magnetic soft-start from the reactor derived from soft-start
The. Three-phase reactor to link the motor stator circuit to achieve lower
Pressure is the common ground between the two. Magnetic soft-start is different from the reactor soft-starting
Movement is the use of magnetic saturation reactor and its electrical resistance value is controlled. Overall
Years, starting the beginning of the reactor reactance values larger than in the soft-start
Process, through feedback regulation so that the reactance value is gradually reduced, till soft play
Action after the completion of bypass.
Magnetic saturable reactor has three pairs of AC winding (per phase pair), and
There's a three-phase DC excitation windings. Where the exchange flow through the windings
Is the motor stator current, it is bound to the DC field winding on the
Induced electric potential. The latter will affect the excitation loop operation. With a pair of
DC resistance around the main purpose is to offset this effect.
High magnetic saturation reactor in principle and structure with low-voltage
(380V) magnetic saturable reactor there is no essential difference, but in some
Has taken a number of special treatment.
Magnetic saturable reactor with a 0.1 S magnitude of inertia, for power
Motivational system large inertia, the magnetic soft-start the inertia is insufficient
To consider the. Some people say that does not produce magnetic soft-start high-order harmonic, which is
Wrong. As long as the saturation, we will certainly be non-linear, it will certainly
Caused by high-order harmonic. Magnetic saturable reactor is generated by high-order harmonic
Than working in the state of thyristor chopper smaller. Soft magnetic effect
Moving devices require a relatively high power auxiliary power supply, noise greater
SR
Figure 3 Magnetic soft-start-line diagram (according to motor stator 6 qualifying draw)
Qs a high-voltage isolation switch QF_ vacuum circuit-breaker
sR a magnetic saturable reactor motor M 1
Is its deficiencies. Magnetic soft-start the main problems faced by such
What is the premise of an effective anti-interference to magnetic saturation reactor capacity to do
Great. Magnetic soft-start-line diagram shown in Figure 3.
1.4 Inverter
Frequency Control Device is also a soft-start device, it is a more
The ideal one, starting when it can be limiting while maintaining a high
Starting torque. The principle is: according to the nature of the load motor drag
And status, changing the motor operates supply voltage (380V or medium -
High-voltage) and frequency (typically 50Hz), so that the different motor drag
Non-load to achieve the best working condition. The good performance of the inverter
Obvious. Its main features are:
(1) conservation of energy, its energy-saving rate up to 20% ~ 80%.
(2) to protect motor and load equipment from transient start Chong
Blow to extend their working life.
(3) improve the motor and load equipment, accuracy of work.
But the inverter technology is still in its period of development, maintenance techniques with the non -
, The product is mainly imported, expensive and other factors, restricted
The popularization and application in China. Inverter itself has soft start and the tone
Two-speed function, if only its soft-start function is much more
Expensive.
The products in the 380V system has a wide range of applications, grouped in the air
Preparation of the medium pressure system also has application performance, such as the China Air Separation Equipment Corporation
Set of Handan Iron & Steel lO00Om / h air separation unit main motor (770OkW)
And the complete set of Chongqing Chaoyang Hang oxygen gas companies 1800Om / h air grouped
Preparation of the main motor.
Autotransformer starting, reactor soft-start, liquid resistance soft-starting
Move, thyristor soft starter, inverter starting performance comparison, see
Table 1.
2 soft-start the industry status quo
Motor soft-start, is a technology, a class of products, a
Industry. Soft-start from imported products, the developed countries, motor soft -
Start main products are solid-state soft-start devices, thyristor soft-start and
Doubles as a soft-start of the inverter. Speed requirements both in the production process
When, of course, use of frequency devices; in the absence of speed required the use of field
Together, the lighter the load when you start (such as fans, pumps) using crystal
Brake pipe soft start; in heavy or particularly large load power only when using variable
Frequency soft-start. Thyristor soft-start device is developed Soft-Start
Mainstream products, the well-known Electric Company, has its own thyristor soft starter
Brand, in its function has different characteristics, able to produce medium-pressure
(6 ~ lOkV) thyristor soft starter products, few manufacturers. Series of Health
Thyristor soft-start device produced a maximum voltage rating of 12kV.
As the liquid soft starter products, shortcomings, in the long run,
Liquid Soft-start products in the field of soft-start difficult to buck a foothold.
According to the author about the developed soft-start production of liquid products, a
Law used in medium voltage soft starter in the wound rotor motor.
In recent years, China-made liquid soft-start device occupies a great deal of domestic
Market share. Simple homemade device is smaller than foreign products, lower cost,
Electrolyte configuration does not use distilled water, liquid containers may also be made of non-sealed.
Chinese-made device to keep popular because it more appropriate to present our country's
Conditions, to meet the minimum soft-start requirements, price, and high maintenance
While the trouble but it is not difficult. In 2002, there are two liquid soft-start
Contrary to the development of noteworthy trends: First, at the expense of controllability
The cost of the soft-start device simplified with the traditional phase-delta starter
Similar system; Second, by improving the servo mechanism of the method is introduced to current
Feedback, closed-loop control to achieve soft-start.
3 soft-start the process of describing device parameters and the pros and cons of soft-start
Rating Project
To be able to objectively and for the installation of the soft-start the process to make more than
Compared and evaluated the following 15 more details. It goes without saying
Comparison and evaluation of all only in the power grid, electric motors, load the same as
Makes sense under the conditions.
(1) soft-start can be completed, as well as start (completion), the
Inter.
(2) soft-start in the process of motor maximum current (pu
Value).
(4) The soft-start motor has the process of abnormal electrical and mechanical resonance
Phenomenon.
(5) soft-start during the current high-order harmonic content (pu
Value).
(6) the price of soft-starting device (often people in the unit volume
Currency indicated).
(7) soft-start device to allow the number of consecutive start.
(8) soft-start device the size of the space.
(9) Soft-Starter current limiting device for easy opening controllability; regulation
Is smooth and fast.
(10) soft-start device on the use of environmental requirements of the margin.
(11) soft-start device start-repeatability (connected to the two soft -
Start "the process description parameters" of the conservation of nature).
(12) soft-start device provided by the start and stop modes
Diversity.
(13) soft-start devices available for the device itself, as well as
Motor function of the completeness of comprehensive protection (including over-current, overload,
Less phase, starting out, grounding, fault tips and display, diagnostic,
Memory, etc.).
(14) soft-start device the size of starting the process of the noise.
(15) soft-start device auxiliary power required for big power
Small.
Value). These items belong to the "device score project", the former five are
(3) soft-start the process of the largest power grid voltage drop (-unit in the "process described in parameters."
4 soft-start the development direction of
The current soft starter market development is very fast, soft starter products
Goods will also be followed to develop, the main direction of development as follows: small size
Model-based, low price-based, intelligent control technology, product specifications Qi
All of the various power perfect.
Short-term outlook; soft starter will continue to be various forms of relief
(Limit) soft-start for its main form. In theory, sex
The price is high and the products will be able to occupy a larger market share. However,
In a variety of applications, people face a variety of performance focus
The same, so that all kinds of starting products (including traditional delta starter) in the
On the market are likely to win their own place. Surface lots of business opportunities focused on
Outlook and subjective aspects. Objective aspects: such as using environmental conditions
(Temperature, humidity range), the start light and heavy loads, using the frequency
Fan degrees, explosion-proof, dust-proof requirements, etc., for example, the South's users
Will not be concerned about liquid soft start fluid resistance will ice; subjective side
Surface: the level of knowledge managers, maintenance personnel, skills,
The management level of user units and so on.
Long-term outlook: frequency soft start will be a soft-start the mainstream.
Advances in inverter technology for universal provision of a reliable technical assurance
※ ※
Inverter is widely used in industrial automation revolution, the only way.
Foreign experts predict the next l0 years, 80% of the power supply to go through the
Power electronic devices over the conversion. On the current development of inverter technology of water
Ping terms, frequency-controlled AC induction motor technology, the mechanical properties
Reached the characteristics of DC motor speed regulator, particularly computer
The use of technology, making converter with rich functionality and the use of square
Characteristics will be making a growing number of experts into its research and
Development areas. Judging from the current widespread use of the VVVF (Variable Pulse Width Modulation
Pressure Frequency) technology development to direct torque control inverter technology, to the
Matrix AC-AC inverter technology, inverter technology becoming more and more into the
Cooked. With prices declining frequency converter, reliability, further
Increase, but also with raising the level of technical personnel in the field of air separation
Choose to use only for the soft-start converter will no longer be considered to be the people
A luxury. Variable frequency soft start winning fundamental reasons are: it can be
In the limit (starting current does not exceed motor rated current value) at the same time
Access to a large starting torque can be achieved, including soft-stop, including the various
Species-start capability. The future field of air separation products into the mainstream of the soft
Starting device will be a full-featured, reliable, maintenance simple, price
The suitable converter.