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It is a high technology content, faster replacement products to achieve uninterruptible power supply (UPS) power conversion and power transmission, which have been widely used in industrial, energy, transportation, finance, information, aerospace, defense, education, culture and other fields. With the rapid development in telecom technology,communication network and IDC, the AC power supply equipment increase. The first edition of communications industry standard YD/T1095 "communication uninterruptible power supply -UPS" was issued and implemented in 2000, which provide the technical basis for the research and development in China's UPS production equipment, testing, engineering design, acceptance and maintenance management.

1 Related UPS communication industry standards

UPS is more and more important in the communications industry, TC4 as an important subject, the related industry standards:

-- YD/T1095-2008 communication uninterruptible power supply (UPS);

-- YD/T1963.4-2009 the fourth technical requirements of Communication Bureau (station) power supply equipment maintenance: uninterruptible power supply (UPS) system;

-- communication modular uninterruptible power supply technology.

1.1 YD/T1095-2008

The first edition of the YD/T1095 was issued and implemented in 2000, providing an important basis for quality inspection operators selection,

based on the many years of experience application, and according to the development of UPS technology and industry current situation, has carried on the revision to YD/T1095-2000, YD/T1095-2008's main index such as table 1.

From the table, input power factor, input current harmonic components and output voltage regulation accuracy are improved greatly compared with the old edition index, Ⅰ, Ⅱunchanged, but dropped the III, so as to improve the qualified threshold; efficiency of low power UPS is increased from 80% to 82%, increased the efficiency index≥ 60kVA type half loaded; The output voltage waveform distortion respectively specified the requirements of Linear and nonlinear load conditions index (2000 edition provides only linear load). These are key indicators, each operator selection test are very seriously, improve energy efficiency indicators in line with the development direction of energy saving and emission reduction, green environmental protection.

1.2 UPS maintenance technical requirements

UPS is the main equipment of communication to ensure continuity of power supply, the operation is the key to ensure the communication security. Like any other communications equipment, it has the failure and redundancy problem, design, installation, use, maintenance and other aspects of the product performance and life have a greater impact, especially in the maintenance must discover in time and handle all kinds of fault, to extend the service life of the UPS, to ensure the safe operation of the communication system.

(1) UPS maintenance items and requirements

Key in the maintenance standard project:

-- UPS and the room should be kept clean, smooth ventilation fan, filter is very important, otherwise it impact he effect;

-- Regular measurement of components and parts, the battery connecting strip temperature rise, promptly discover the hidden safety trouble;

-- Regular measurement of UPS voltage, input voltage, input parameters of frequency, input current harmonic component, the input power factor, efficiency, output voltage, output frequency, output wire-zero line waveform, battery charging current, should comply with the relevant requirements;

-- for the parallel redundant system, should regularly check the load sharing performance.

(2) Project approval and requirements

First, Distribution switch capacity rating verification before or after the setting value, function can meet the normal requirements of load

First, check the ratings or setting value and function of the before and after the level switching capacity, whether to meet the normal requirements of the load, whether to meet input / output wire diameter standard, the method is correct and clear, and in accordance with the requirements of YD/T1095-2008 measurements of the electrical properties and functions. In the field, due to multiple UPS devices have been installed in place, the connection is completed, the official use of the former is fully tested and machine function is very necessary and feasible, as follows:

-- UPS parallel operation with half load, record each output current, calculate and machine load current unbalanced degree;

-- Close for one or more UPS, and then re-enter, check the output voltage waveform whether has obvious change;

-- UPS parallel operation with half load, close for each UPS city electricity, bypass input analog switch, simulate power cut, then restore the city power supply, check the UPS output voltage waveform whether has obvious change;

-- UPS parallel operation with half load, and then transferred to the power supply unit, and then fell back to the mains supply, check the UPS output voltage waveform whether has obvious change, measurement of UPS frequency tracking speed.

(3) The key device and its life

This prompts the user can not ignore the maintenance and replacement of key device in UPS work period:

-- The working life of filtering electrolytic capacitor has some connection with environment temperature, voltage, ripple current and harmonic current and other factors, electrolytic capacitor filter suggestions work for 6 ~ 7 years, or according to the requirements of equipment replacement after 5 years, if explosion-proof valve cracking, surface bulging or leakage, should be replaced immediately;

-- Fan suggestions work for 6 years, after 5 years should be replaced, routine maintenance should check the fan speed and noise, when an exception occurs should be immediately replaced.

1.3 Modular UPS

(1) The advantages of modular UPS

Modular UPS has the following advantages, the application in communication industry gradually increased in recent years:

-- Scalability: convenient for expansion and upgrade;

-- Maintainability: with online hot swap function, add and subtract module without to bypass;

-- Green energy: high efficiency, low input current harmonic components;

-- High cost performance: reduce the purchase cost, maintenance and future expansion stage equipment operating costs;

-- High availability: effectively reduce the mean time to repair MTTR, improve the availability of power supply system.

(2) The definition of modular UPS

UPS has a modular architecture characteristics of N+X", consist of input distribution, power distribution, power module, monitoring module, the power module with structure and power conversion function integrated in the machine, system circuit topology as shown in figure 1.

         (3) Concerns

        The standard considers the following issues:

        -- The hot swap function: to improve the ease maintenance of system, online maintenance in a redundant permission, to achieve "zero repair time";

        -- Each module fault isolation and shock resistance: with automatically exiting function when power module fault, power module fault should withdraw from the of power system operation , that does not affect the normal work of other parts of the system, and ensure the safety of power supply;

        -- Detailed provision on a variety of current imbalance, circulation and other parameters: if the input current imbalance, bypass current imbalance, the output current is not balanced, no-load output loop mobility etc..

        2 Analysis of UPS test

        UPS input power factor, input current harmonics, voltage waveform distortion and power efficiency are worth considering in selection test by operator. In addition to these parameters and components quality and matching on the outside, also relation of the working principle, circuit structure and design.

        2.1 Comparison of high frequency machine and power machine

        The rectifier part of the UPS according to the different design of the operating frequency of the circuit can be divided into high frequency machine and power machine. High frequency machine adopts the high frequency of the PWM and microprocessor control technology, the power machine adopts the principles of analog circuits. Except for the difference between the volume and weight, the index parameter also different, figure 2 shows the input power factor, input current harmonics, the output waveform distortion, power efficiency and other parameters of the statistical data, the external filter frequency of power machine decline in the efficiency of about 1%.They should be selected according to the needs of customers, the installation environment, load balance and other conditions.

 

        2.2 Comparison of rectifier mode

        The working principle of UPS rectifier can be divided into IGBT rectifier, 6 pulse mode, 12 pulse mode and controlled rectifier +IGBT boost circuit, figure 3 shows the various rectifier mode UPS in statistical number, full of light load, resistive load, nonlinear load conditions the four parameter, different operating principle of the UPS makes a great difference in output parameters .

        2.3 Comparison of the filtering methods

        UPS Filter have a great effect on the technical indicators, figure 4 shows the statistical data when the UPS in the conditions of full load, light load, resistive load, nonlinear load with three modes of no filtering, only the passive filter and the passive filter+ active filter.