Key word: Correspondence power source rectification module choice

1 introduction

Must consider very many factors for a correspondence electrical power system choice rectification module. In the past, the big monopoly telecommunication company frequently chose �?the remainder very big system plan. But, is day by day intense along with the global market competition, this choice way will be cannot be taken. In order to optimize a power source power supply plan, it is necessary carefully to inspect many correlation factors, including the product performance and the price question, can satisfy the end-user like this by the most economical way the request.

The various countries in the law unceasingly to the product security and EMC proposed the new request, causes the choice power source plan the condition to be harsher. Provides the most superior plan for each application situation is necessary, but starts for this to design each system actually is not feasible from the beginning. Feasible is the use standard module disposes the system.

The rectification module is the electrical power system heart, elects the module is not correct, is very difficult to provide the most superior electrical power system disposition. This article has studied with the module related many factors as well as the module movement environment, and provides the choice correspondence electrical power system rectification module from the logic the method.

This article involves the scope only to be restricted in single-phase 200W ~ 6kW the rectification module. But many mentalities may apply on other power sources.

2 coolant conditionses - forced-air cooling and self-cooling choice

A system coolant conditions has the extremely tremendous influence to the rectification module choice. Some systems request natural cooling (abbreviation self-cooling), some may accept the ventilator to cool (abbreviation forced-air cooling). Under the similar power, the same level condition, the forced-air cooling and the self-cooling module biggest difference lies in the contour size and cost how many. In the western big telecommunication company tradition chooses the natural cooling, like this may obtain the longer product life, the obvious low maintenance cost, the power source initial cost does not look like the present such expensively (present self-cooling module to be very expensive). Thus, the choice �?remainder very big system plan also may accept, it may safely supply power.

The forced-air cooling module is counterbalanced in the cost and the size superiority by its shortcoming (for example noise, dust, ventilator life and reliability), but these shortcomings certainly are not the most most important consideration questions in fact. An outer covering designs the very bad self-cooling module reliability compared to use the forced-air cooling the module to have to lower a lot, because forced-air cooling module cooling has nothing to do with with the outer covering design. Moreover, forced-air cooling product key - semiconductor device compared to self-cooling system 温升 lower, thus is more reliable.

When the request design life surpasses for 7 years, in the tradition does not use the ventilator. But, if allows regularly to replace the ventilator, has the possibility to obtain designs the life longer forced-air cooling system. If the forced-air cooling rectification module designs has the ventilator performance monitor, the scene is easy to replace the ventilator the characteristic, then the permission system obtains the redundant reliability by the low cost. Since more than 20 years both have wanted the economy to the rectification module, and to want the long life the design request are the conditions which the forced-air cooling product can survive.

Forced-air cooling and self-cooling technology mentioned which besides above, moreover two kind of technologies also more and more popular: External system cooling and assistance cooling.

2.1 external systems cooling

External system cooling is refers by the central cooling system provides the air current to carry on cooling to the rectification module. This method may obtain the power density, moreover has avoided some shortcomings which the module power source internal installation ventilator brings. This integrates the supplier for the OEM application in the electrical power system which in the entire communications system goes to bring the remarkable profit. For instance:

Central cooling system, not only provides the air current to the electrical power system, also cools other parts of communications system. In a system only has a central cooling system to need to maintain, when the central cooling system breaks down the power source still could the output energy (approximately for full load time 60%).

2.2 auxiliary forced-air coolings

The auxiliary forced-air cooling is refers to the module cooling is provides by the interrupted movement ventilator. When the hyperpyrexia or continues outputs the big electric current, the ventilator can revolve. Selects this method to be allowed to obtain the very high system integration rate, but needs frequently to let the ventilator revolution and regularly to examine its performance. If the ventilator work is not normal, can send out the alarm. This method advantage includes:

In does not replace in the situation, the ventilator interrupted revolution causes the system design life to force the forced-air cooling the module in to have to be longer than.

If the consideration redundancy and the battery charge, in the module ventilator does not transfer in the normal condition.

Because the ventilator interrupted movement, the dust and the noise question also greatly alleviates.

How below explains with examples disposes the system:

Rectification module:

Time natural cooling capacity 30A

Time auxiliary forced-air cooling capacity 50A

Load:

大负�?110A

Battery charging current 30A

Joint current 140A

The request uses the N + 1 redundant backup.

Must support 140A the output capacity to have to choose 3 rectification modules and 1 redundancy spare module. If 4 modules all worked (practical application) moreover the battery have so filled the electricity, each module most 大负�?the electric current only had 110/4=27.5A, was lower than the module self-cooling rated capacity. This time the ventilator does not transfer. When the power cut charges to the battery, when or a module breaks down, the system still will answer the purpose, but the ventilator started to revolve. In the model system, the ventilator operating time proportion is extremely low, this greatly lengthened the product life. Moreover, according to above example, after some module ventilator breakdown the system capacity only reduces 10% (from 4×50A to fall to 3×50A + 30A). If uses forces the forced-air cooling module, the system capacity will reduce 25%.

Table 1 has produced under each kind of coolant conditions typical power density.

Table under 1 each kind of coolant conditions typical power density *

Coolant conditions relative capacity density
Natural cooling 1.00
Forces forced-air cooling 2 to 2.5
System forced-air cooling 1.5 to 2
Auxiliary forced-air cooling 1.3 to 1.7

* The hypothesis all movements environment has the commeasurability.

3 input voltages scope choice

Is more and more important for the specific application situation choice correct input voltage scope. In England, in the past the usual definition input voltage scope was 216V ~ 264V (namely 240V±10%). Now tends to uses suits to the world general voltage scope: 85V ~ 264V (or is wider). In the practical application two 极端�?(85V and 264V) all are not most appropriate.

In order to satisfy internationally on stipulates to inputs the overtone the request, developed had the 110V power input factor compensating circuit the rectification module, thus enable the product to have the whole world general input voltage scope.

Says regarding the mobile equipment market or the global use equipment market, chooses the belt power factor to adjust, the general input module is correct without doubt, but regarding fixedly installs said, carefully chooses the input voltage scope to be able to have the very big advantage. Will have to provide the complete performance in the width voltage scope to be able to give the rectification module to bring in the cost and the size remarkable increase. This also can affect system cooling. In the practical application the rectification module work in the 85V input voltage time loss is time 230V two times.

Obviously, sometimes must provide the complete performance in the width voltage scope. But in certain situations, when the input voltage is lower than some threshold value only requests in the short time to provide the complete performance, like this does not need to deal with the radiation issue, thus remarkably reduced the cost and reduced the volume.

If system work under 115V fixed input voltage, then moves in 103□�?V (115V - 10%) the time loss and the movement differs 15% in the 85V time loss. The request above 85V will be able the continuous working system when 103□�?V than the continuous working system to have to lose 15% power. The continuous working in 103□�?V under certainly did not mean the system cannot reliably the short time work under the very low voltage. The regarding this accuracy control will be decided in the module the temperature monitoring circuit.

Chart 1 has produced between the model power loss and the input voltage relations.

4 limits flows the characteristic

The usual electrical power system has the constant current characteristic in the entire voltage output scope, when short-circuiting the output voltage, the electric current drop by the broken line or the straight line. This traditional way is not certainly ideal. Pondered the load all real characteristics may enable the system to obtain the optimization.

Adds on a correspondence electrical power system the load is many small loads sum totals in fact. Some loads are the resistance, some are the continuous current, some are the permanent power, the battery also can cause the charging current change because of the charge condition change. If the system works under the highest battery 浮充 voltage biggest overall load electric current (contains battery charging current) to determine its capacity, then can the rich Yu Henduo power supply capacity.

More and more many equipment use in the system in the modern communications system to set at the DC/DC converter, it may not provide the continuous current voltage which changes along with the electric power supply output generatrix voltage change. This kind of permanent power characteristic request when generatrix voltage drop input current increase. If permanent power load in 55V time consumes 1A, then in 40V time consumes 1□�?A. But permanent resistive load when 55V consumes 1A, when 40V only consumes 0□�?A. Carefully analyzes in the entire working voltage scope all loads actual situation can know that, whether may be different through one kind to the traditional continuous current limits flows the characteristic to optimize the system.

Following method may use for to determine whether uses optimized the characteristic curve. Supposition:

Time Id - 40V DC/DC biggest input current

When Ir - 55V biggest resistance electric current

Ib - constant battery charging current

It - overall load electric current

Then in 55V time:

It=Id×40/55 + Ir + Ib

When 40V:

It=Id + Ir×40/55 + Ib

Supposes the normal 浮充 voltage is 55V, the lowest battery voltage is 40V.

Example 1

Supposes: Id=100A, Ir=20A, Ib=10A

When 55V:

It= (100×40/55) + 20 + 10=102.7A

Is equal to 5□�?4kW power.

When 40V:

It=100 + (20×40/55) + 10=124.5A

This is equal to 4□�?8kW power.

Example 2

Supposes: Id=50A, Ir=70A, Ib=10A

When 55V:

It= (50×40/55) + 70 + 10=116.4A

Is equal to 6.4kW the power.

When 40V:

It=50 + (70×40/55) + 10=110.9A

This is equal to 4.44kW the power.

In example in 1, if uses the partial permanent powers characteristic electric circuit in the module, may from 6□�?5kW (124.5×55) reduce the maximum work rate 5.64kW, saved 17% to be also many.

In the example in 2, in the entire working voltage scope, the electric current falls very much few along with the voltage drop, therefore suits in the rectification module has the continuous current characteristic electric circuit.

The modern switch type analysis situs technology may easily achieve according to the overall load requests to determine the input level, causes under the certain load combination to reduce the always installment power also to be able to answer the purpose.