Smps 6w4u2q

SMPS POWER PLANT Power plant basic concepts: Power plant is equipment, which gives uninterrupted DC power supply to the telecommunication systems. Because telecommunication systems require electrical energy for (a) Conversion of speech signals to electrical signals (b) For operating switching, transmission equipments Need of D.C. Power supply     

Harmonics of A.C may affect the speech signals. Relays used in telecom systems are more sensitive to D.C than A.C Transistors and I.C.s etc. being unidirectional devices, the use of D.C has become necessary. Arranging standby source to A.C is difficult compare to D.C for which secondary cells can be used as S/B source. Not hazardous to human life.

Sources of power: Telecommunication systems need uninterrupted power supply round the clock and throughout the year. For any uninterrupted power supply system, two sources are required. 1. Normal or Main source-Main Source is D.C derived from commercial source. 2. Secondary or standby source- Secondary cells By name we can define “Normal source is one which supplies power to the load round the clock” and “secondary source is one which supplies power to the load only during the absence of power from normal source”. “Hence it is a must to convert AC from commercial mains to D.C.” A.C to D.C conversions: Previously M.G (Motor-Generator) sets were used for A.C to D.C conversion. In this A.C motor rotates on commercial A.C. supply. To the shaft of this AC motor, D.C. Generator will be coupled which generates D.C. Now a days static rectifiers using static electronic components like metal or diode rectifiers are used.

Advantages of static rectifiers compared to M.G. sets. a. Complete absence of rotary parts. Hence no wear and tear, Maintenance is easy, Long life. b. Regulation is easy without involving any moving mechanism. c. Conversion efficiency is high. d. Space occupied is less. e. Rectifiers can be paralleled automatically to meet the exchange load during peak hours. Float working Parallel Battery Float Scheme.

In this scheme two sets of Batteries (24 cells each set) are connected in parallel to the output of the rectifier. The output of the rectifier is 51.5 V. Hence floating voltage of each cell is 51.5 divided by 24 = 2.15V/ cell. Hence always 90% of battery capacity will be available for emergency usage For the operation of the scheme “POWER PLANT” is designed by TRC (Telecom Research Centre) Operating voltage: Now a days almost all of our telecom equipment works on -48 volts D.C. supply i.e. positive lead is earthed. Earthing of one pole of D.C:

Reasons for earthing of one pole of D.C are as follows: a. Switching can be single pole. b. Cross talk and other disturbances can be avoided. c. To make the alarm and supervisory system easy. d. Earth return signaling can be used. Reasons for earthing positive pole of D.C a. In electrolysis positive electrode will be normally corroded. If we keep our lines and equipment at negative potential, we can minimise troubles from the corrosive effects. b. Partial Earth faults can be definitely identified if the conductor is negative. Otherwise fault is liable to seal up owing to oxidation. Power plant consists of a. Float rectifier b. Battery Charger c. Switching Cubicle.

FLOAT RECTIFIER The function of the Float Rectifier is to receive three phase 440 V AC and to give a constant 51.5 Volts D.C without AC ripples. The steps involved to achieve the function are a. Step-down b. Rectification c. Filtering d. Regulation. Step down Transformer steps down the 3 phase A.C voltage from 440 volts to around 80 volts. Rectification Any unidirectional device rectifies the AC to DC. Here Diodes & SCRs are used for rectification. Filtering: Here multi-stage L.C. Filters are used for filtering the A.C. Ripples. Regulation:

What is Regulation? As far as Float Rectifier is concerned,” Regulation is the mechanism by which the output of a float rectifier is kept constant at 51.5  0.5V irrespective of input voltage variations of ± 12%. Output load variations of 5% to 105% and input frequency variations of ± 4% or 48-52 Hz”.

Why Regulation is required? Float rectifier should not only supply power to the load but also takes care of its battery sets, which are floated across its output. If the float rectifier output voltage is 51.5v, the cells are floated at 2.15v/cell and hence they are continuously trickle charged and this compensates losses due to selfdischarge or local action. If FR output is 49.2V, the battery set is not trickle charged, hence trickle charging is to be given once in a fortnight. If FR output is <49.0V, the battery starts discharging. If FR output is >51.5V, the floating voltage of each cell will be > 2.15V and the battery will be over charged. Hence regulation is required. Various regulation methods: 1. By “Transductor or saturable reactor or magnetic amplifier” method. 2. By SCR method. 3. SMPS method. The three methods, Controls the portion of the input A.C cycle to feed to rectifier so that output voltage gets regulated. By “Transductor or saturable reactor or magnetic amplifier” method.

In this a transductor is placed in series with the rectifier and uses the principle that the impedance of an iron cored coil can be varied by varying the degree of saturation of the core.” By varying the series impedance to rectifier, we can vary the portion of input cycle that is fed to Rectifier.

SCR Method. In this the SCR is used as rectifying element. Let us recapitulate the working of SCR.

In the normal 'off' state the device restricts current flow to the leakage current. When the gate to source current exceeds a certain point, the device turns 'on' and conducts current. The device will remain in the 'on' state even after gate current is removed so long as current through the device remains above the holding current. Once current falls below the holding current the device will switch off. If the applied voltage increases rapidly, it may induce enough leakage current to trigger the device into the on state, but this is harmful to the device. The reverse blocking voltage is limited in any device.

SCR can be switched on by applying the positive pulse to the gate. Once if the SCR is switched on, it will be in ‘ON’ condition as long as the current flowing through SCR is above a threshold value called “Holding current”. In a Float rectifier, across each half cycle one SCR is connected. Hence for 3 phases i.e. R, Y, B totally 6 SCRs connected. Let an SCR is connected across the positive half cycle of a phase. The total time period of an half cycle is 10 ms. Within this half cycle triggering pulses

can be given at any time. Assume that triggering pulse is given to SCR at Point ’A’ after 4 ms of starting of the half cycle, the SCR will be on. Even though the triggering pulse is removed, the SCR will remains on. But the current flowing through SCR depends on the amplitude applied across its terminals. At 9 ms i.e. @ point B, let the current flowing through the SCR is just below the holding current. The SCR will be switched off. That means “switching on” of SCR is in our hands, but “switching off” of SCR is not in our hands, it is automatic. In this case the portion of half cycle between the points A and B is rectified. The output voltage of the FR depends on both the input AC voltage and output DC load and position of triggering pulse advanced or delayed

-Look at the above table. Whenever the input voltage increases or output load decreases the output DC voltage increases and vice versa. Hence if we monitor output voltage, it is sufficient to regulate it. -If the output voltage is increased, then the triggering pulse to the SCR will be delayed or retarded, point A moves towards B, hence the portion of AC cycle rectified will be reduced, hence output voltage will be automatically reduced and brought to the specified value.

-If the output voltage is decreased, then the triggering pulse to the SCR will be advanced, hence output voltage will be automatically increased and brought to the specified value. -This is how regulation is achieved by using SCR.

SMPS POWER PLANTS(ITI Make) (Suitable for VRLA Batteries with 100A SMPS Rectifier Modules) Introduction The power system is intended primarily to provide uninterrupted DC power to Telecom equipments and current for charging the batteries in the presence of AC Mains. The system works from commercial AC mains which is rectified and regulated to –50V DC and is fed to the equipment (exchange). The system has provision to connect three sets of VRLA batteries and facility to charge them simultaneously to ensure that uninterrupted DC power supply is always available to the exchange.

The power system –50V, 2000A has the following features: a. Multi-rack configuration. b. Facility to parallel a maximum of 21 nos. (or 22 nos.) of 100A (5600W) rectifier modules operation from three phase, 400V, 50Hz AC input. c. Termination for three sets of VRLA batteries and exchange load. d. Input : Three phase, 4-wire, 50 Hz supply. The power system as a single DC bus called auto float/charge bus. Depending Up on the status of the batteries, the output DC voltage is maintained at 54.0 + 0.5 V under auto float condition. During auto charge the maximum DC voltage reached across the bus is 55.2 volts. The exchange battery and rectifier modules are connected in parallel. The system employs natural convection cooling and has AC input distribution, DC output distribution, protection and alarm circuitry for rectifiers, battery and equipment. Technical Specification For Module 1. Input Voltage : a. 320V to 480V r m s three phase (Nominal Voltage – 400V). b. Frequency: 45 Hz. 65 Hz.

2. Output Voltage : Float mode : Nominal voltage : -54.0 + 0.5V, Adjustment range : -48.0 to –56.0 V Charge mode Voltage : -55.2 + 0.5 V 3. Rated current : 100 Amps. 4. Psophometric noise : Less than 4 mV without battery floated. Less than 2 mV with battery floated. 5. Input power factor : Greater than 0.95 lag with 25% to 100% load at nominal input. 6. Efficiency : Greater than 90% at full Load and nominal input. 7. Protection : a. b. c. d.

Short circuit protection. Input over/under voltage protection. Output over voltage protection. Constant current features settable from 80 Amps. to 110 Amps. in auto float/charge mode.

8. Alarms and indicating lamps: a. b. c. d. e.

FR/BC on Auto Float/Charge Rectifier module over voltage DC output fail/Under voltage FR/BC Over Load (Voltage Drop) Mains Available

: Green LED : Red LED : Red LED : Amber/Yellow LED : Green LED

For System 1. Input Voltage: a. 3 Phase, 4 Wire, 50 Hz (Range – 320V to 480V RMS) b. Frequency : 45 Hz …. 65 Hz. 2. Output Voltage : a. Float mode Voltage : -54.0 + 0.5V b. Charge mode Voltage : -55.2 + 0.5V 3. Rated Current : a. Equipment : 1100 Amps.

b. Batteries

: 300 Amps. Each

4. Protection a. Short circuit/Over load protection. b. Input over/under voltage protection. c. Battery/Equipment over voltage protection.

5. Alarms and indicating lamps : a. Load Voltage High b. Load Voltage Low c. Fuse Fail d. FR/BC Fail (FR/BC No Output MCB Trip) e. Mains available f. Mains out of range g. Mains Fail h. System (Exchange) Overload i. FR/BC Float/Charge Mode j. Mains “ON”/Battery Discharge

Functional description of power system

- Red LED - Red LED - Red LED - Red LED - Green LED - Red LED - Red LED - Red LED - Green LED - Red LED

This Power System is of multi rack type and consists of the following:

a. Eight racks – One main, one auxiliary and six extension racks. b. AC Distribution module in each rack. c. Rectifier modules (A maximum of three modules in extension rack and two each in main rack and auxiliary rack). d. DC distribution module in each rack. e. Metering in each rack. f. Power system controller in main rack.

a. Rack: The rack is made of mild steel profiles with hinged front door. The door accommodates display and alarm enunciator. The rack is convection cooled and has ventilatory slots in the front and sides. The rear is screw type and can be dismantled. The cabinet accommodates 19” subsystems. Air baffles are provided for better heat transfer. Depending upon the load

requirement (Equipment and Batteries), additional modules can be added. The bottom and top also have ventilatory features. The DC power termination and distribution is done at the top. The AC power termination and distribution is done at the bottom. b. AC Distribution : The AC input to the rack is terminated at the bottom of the rack on screw type terminals. Individual AC circuit breakers are provided for each module. The line neutral and earthing cabinet are terminated on moulded plug, which is fixed to the respective sockets on the rectifier module. To monitor AC input current, 3 nos. of single-phase AC current transformers are mounted on the of main rack. A small signal transformer is mounted on the PSC to provide AC input to power system controller card. c. Rectifier module : The SMPS rectifier module – 50V, 5600 watts works on 400V AC input and provides – 50V DC for system. The input is through 9 pin AC socket and the DC output is through terminals. The module has front to indicate status and faults in the module. The control signal is taken through 8 pin telephone jack and is terminated on to the power system controller card. The rectifier modules are convection cooled and can be jacked in and out of the cabinet easily. The DC output from each module is terminated on the respective DC bus bar mounted on the DC distribution . d. DC Distribution : This is mounted at the top of the cabinet. The incorporates the following : (1) Input from individual rectifier modules terminated on cabinet. (2) DC shunts to monitor current in various paths. (3) Termination of battery 1, 2 and 3. (4) Termination of equipment positive and negative. (5) Fuses for battery 1, 2 and 3. e. Metering: The front of main rack consists of two AC meters to monitor individual line to line voltage and current. The selector switch selects the relevant phases. The DC meters monitor both voltage and current of batteries and exchange. f. Power system controller : The Power system controller card consists of an electronic circuit which monitors the state of each rectifier module and display their status. It also controls the operation of 57 the module so as to make it work in auto float or auto charge mode. The current signals are monitored continuously to ensure equal sharing of current. In case of faults, the same is displayed and for faults like input voltage beyond limits, DC output over voltage, over load etc. it shuts off the module. The various alarms as per following details are displayed on the front with audible alarm.

1. Mains out of range 2. Load voltage high (above 57V) 3. Load Voltage low (below 42V) 4. Mains fail 5. System overload 6. Mains available 7. System over load 8. Mains on battery discharge 9. FR/BC in Float-charge mode 10. FR/BC Fail

: Red : Red : Red : Red : Red : Green : Red : Red : Green : Red

Functional Description of Rectifier The SMPS 50V-5600W rectifier is a state-of-the-art switch-mode power conversion equipment. The unit consists of two cascaded power converters performing power factor correction and DC/DC conversion. The power stages are synchronized and working with constant switching frequency of 100 kHz. The rectified AC mains voltage is processed first in the power factor corrector circuit, which is based on a boost topology. The boost converter has the inherent advantage of continuous input current waveform, which relaxes the input filter requirements. The performance of the basic boost cell is improved by a proprietary snubber circuit, which reduces the switching losses of the power semiconductors due to non-zero switching times. Furthermore, the snubber circuit also decreases the electromagnetic interference (EMI) generated primarily during the turn-off process of the boost diode. The output of the boost converter is a stabilised 400V DC voltage. Further conversion of the stabilised high voltage output of the power factor corrector circuit is necessary to generate the isolated low voltage output and to provide the required protection functions for telecommunication application. These tasks are achieved in the DC/DC converter circuit which is based on a full-bridge topology. The full-bridge circuit is operated by phaseshift pulse with modulation with current mode control. This control method provides zero voltage switching condition for all primary side power semiconductors effectively reducing switching losses and electromagnetic interference. An advanced solution reduces the stresses of the output rectifier diodes. Proper operation of the power converters is managed by individual controller circuits and supervised by the housekeeping electronics. Remote commanding and monitoring of the modules are possible through a power system controller housed in the system. Functional Description of Power System Controller Power system controller is designed to control the modes of operation of rectifiers, acknowledge and displays the status of rectifiers and system and controls parameters of rectifiers. The controller accepts signal from individual rectifiers through 8 pin telephone jack and controls the operation of each individual rectifiers. The mode of operation of rectifier modules depends on

the coded signal M1 and M2 from the controller. Depending on the state of batteries, the ATM circuit either gives a signal for float or charge. These signals are encoded by an encoder to obtain suitable coded signals M1 and M2. Depending upon the mode of operation of Rectifier modules, they acknowledge coded signals S1 and S2. These signals are decoded to display whether the modules are in auto float/charge or fail condition. The total battery current can be suitably programmed to limit the current supplied from the modules through current programming pin in modules. SMPS 48V – 5600W – Introduction The SMPS 48V-5600W is a three-phase, unity power factor power supply with a wide input voltage range of 3 X 185 Vac to 275 Vac (with neutral wire) and with a useful output power of 5600W delivered to the load. This unit has been developed for cost effective but highly intelligent modular telecommunication power systems. It fulfills the specification of Primary application of the rectifiers SMPS 48V-5600W are in the supply of Telecom equipment. The convection cooled unit may be operated up to 60C ambient air temperature. The rectifier operates from a nominal 3 X 230 V ac rms (with neutral wire) source. The mains frequency may vary from 45 Hz to 65 Hz. Total harmonic distortion (THD) of the input current wave form is below 5%. The output of the rectifier conforms to the generic requirements of telecommunication power supplies in of noise, voltage programmability, as well as over voltage, overload and short-circuit protection. The rectifier SMPS 48V-5600W can be set in the 3 modes ‘auto float’, ‘auto charge’ and ‘manual boost’ by the power system controller.

General description of operation

The SMPS 48V-5600W rectifier is a state-of-the-art switch-mode power supply. It is composed of 3 identical single-phase sub-modules (R, S and T) as shown in the block diagram : The sub-modules are connected between neutral and one of the phases (R, S or T) on the input, and in parallel on the output. All ‘-‘ wires are protected by circuit breakers, which are mechanically coupled.

The interface card IFC 52 provides : 1. all reference voltages and protections to the sub-modules. 2. Signalisation and manual interface (adjustment potentiometers and test jacks) for the whole unit, and 3. Communication with power system controller ‘ITI’. Each of the sub-modules consists of two cascaded power converters performing over factor correction and dc/dc conversion. The power stages are synchronised and working with constant switching frequency of ~100 kHz. The rectified ac mains voltage is processed first in the power factor corrector circuit which is based on a boost topology. The boost converter has the inherent advantage of continuous input current waveform, which relaxes the input filter requirements. The performance of the basic boost cell is improved by a proprietary snubber circuit, which reduces the switching losses of the power semiconductors due to non-zero switching times. Furthermore, the snubber circuit also decreases the electromagnetic interference generated

primarily during the turn-off process of the boost diode. The output of boost converter is a stabilised 400 Vdc voltage. Further conversion of the stabilised high voltage output of the power factor corrector circuit is necessary to generate the isolated low voltage output and to provide the required protection functions for telecommunication application. These tasks are achieved in the dc/dc converter circuit, which is based on a full-bridge topology. The full bridge circuit is operated by phase-shift pulse-width modulation with current-mode control. This control method provides zero voltage switching conditions for all primary side power semiconductors effectively reducing switching losses and electromagnetic interference. An advanced solution reduces the stresses on the output rectifier diodes. Proper operation of the power converters is managed by individual control circuits and supervised by the housekeeping electronics. Remote commanding and monitoring of the modules are possible through a power system controller. Block diagram of a single sub-module R, S or T This chapter gives more detailed information about the technical merit of single sub-module based on the functional blocks shown in the diagram below (R, S and T).

Input Section Block 1 of the drawing presented above is the input EMI filter of the rectifier. The fixed frequency, synchronized operation of the different circuits allowed to optimise the filter’s performance. It has only one differential and one common mode filter stage. Block 2 represents the Inrush Current Limiter circuit, which consists of series combination of surge rated power resistors and fuse. The circuit limits the input current of the rectifier during the initial charging of the energy storage

capacitors connected to the output of the boost power factor corrector circuit. In normal operation the current limiting components are by-ed through relay, which is controlled by the housekeeping electronics. A general purpose full-wave Bridge Rectifier circuit forms Block 3. It is directly mounted on the heat sink. Power factor corrector The power stage of the Power Factor Corrector is a boost converter represented by Block 4. The circuit operates with 100 kHz constant frequencies in continuous inductor current mode. Because of the relatively high switching frequency a loss-less snubber has been added to the basic boost converter to reduce switching losses and semiconductor stresses. When the boost transistor conducts the energy being stored in the boost inductor increases. During the off state of the transistor energy is transferred from the inductor to the output capacitor through the boost diode. The inductor current is measured with a sense resistor and it is forced to follow the input voltage wave form. The technical literature refers to this technique as the resistor emulation mode which is the most preferred load by the utility companies. The output Capacitor of the boost converter is marked by number 5 in the block diagram. This capacitor is used for low-frequency energy storage as well. Due to the nature of ac sources the energy absorbed at the input of the unit varies according to the mains cycle. In order to deliver constant power at the output energy must be stored inside the unit. Therefore, high voltage 450V electrolytic capacitors are used at the output of the boost converter to provide cost and volume effective energy storage. Block 12 is the controller of the Power Factor Corrector. It uses the UC3854B integrated circuit which had been developed to control boost converters in power factor corrector applications. This integrated solution takes care about all sensing, controlling and protection functions which are necessary to achieve proper input current wave form and to stabilise the output voltage of the power factor corrector circuit. The control principle implemented in the UC3854B is average current mode control. DC/DC Converter The heart of the module is the dc/dc Converter shown in Blocks 6-9. Block 6 shows the primary arrangement of the full-bridge power converter employing a safety isolated high-frequency transformer. Because of its important role in providing safety isolation between the input and the output of the module, the transformer coupling is emphasised in Block 7. The secondary side of the dc/dc stage provides rectification (Block 8) and filtering (Block 9) functions which are realised using current-doubler topology. Particularity of the implemented solution is integration of two inductors on a common ferrite core. The full-bridge converter takes energy from its input when two diagonally located switches are turned on at the same time. This energy is

transferred to the output through the transformer immediately. The energy will be stored in the output filter inductor showed in Block 9 and transferred to the output capacitor of the dc/dc converter during the ive interval when energy is not absorbed from the source. This sequence can be achieved by different ways depending on the implemented control strategy. The dc/dc Controller, shown in Block 13, is using the phase-shift pulse width modulation technique which provides loss-less, zero voltage turn-on condition for the primary side semiconductors. Further benefit is the greatly reduced electromagnetic interference generated by the converter. The control principle is peak current mode control. Like the power stage, the controller circuit of the dc/dc converter is also divided between the primary and the secondary side of the rectifier. Communication between the separated parts are realised using optical isolators marked by number 14. Major part of the dc/dc controller is referred to as Secondary Controller in Block 15. The secondary side controller is responsible for output voltage and current regulation functions. Output Section Block 10 forms the physical Output Section of the sub-module. It is a shielded, common-mode, low- filter stage to reduce conducted electromagnetic interferences to the required level. Housekeeping The name Housekeeping refers to the auxiliary power supply and to all internal primary side supervisory functions necessary for the operation of the unit. Besides theauxiliary power converter (current-mode controlled fly-back converter), Block 11 also includes the master clock, under- and over-voltage lock-out, and start-up sequence generator. Output Characteristics The power system controller can set the rectifier into the 3 modes of operation, i.e. ‘auto float’, ‘auto charge’ and ‘manual boost’. The output characteristic is different for these 3 modes as shown below : ‘auto float’ mode

‘manual boost’ mode

‘auto charge’ mode

TESTING PROCEDURE OF SMPS POWER PLANT

1.

Scope

This Engineering instructions describes the testing procedure of “High Frequency Switch mode Power Supply“ (SMPS) power plants, which is mainly to evaluate technical parameters & functional aspect of SMPS techniques used in Telecom Network. 2.

General

With the advent of digitalisation in the arena of power supply system, conventional power plants are being replaced by “High Frequency Switch Mode Power Supply” System called SMPS power plants. These plants are of different capacities i.e. 12.5A stand alone module to 7000A Rack Power System, arrived by using compact (SMR-Switch Mode Rectifier) package; rack power system is used to supply uninterrupted (using suitable VRLA battery back up) and disturbance free DC power for Telecom equipments. Since these SMPS power plants used MOSFET’s, FET’s in SMR’s (Switch Mode Rectifier), microprocessor controls etc. it has a typical testing procedure as described below: 3.

Testing instruments

The instruments required are 500 Volts Insulation tester, Standard A.C. Ammeters, Voltmeter, DC mV volt calibrator, Voltmeter, Tong tester Digital Multimeter, Psophometer, Thermometers, Earth tester & DC load. 4.

Tests

4.1 LAR: Location alignment & rigidity of the unit is checked as per approved plan and ensured that physical mountings of all SMR’s plugged-in securely in magazines. 4.2 Earth testing: Check (as given below), that a good earth, of value  0.5  is connected with power plant. Suitability and gauge of earthing lead should also be checked as per specification. Method of measuring Earth Resistance (4 terminal) Drive two ground rods (auxiliary electrode) 2 feet deep, in a straight line. The 1st electrode (p1)20 meter away from earth, and 2nd electrode (c1) 40 meter away from earth under test. connect the wires taken from p1 & c1 to p1 and c1 terminals of the tester. Also connect the earthing under test at p2, c2 shorted together terminals. Turn the handle at rated speed or above. The value indicated as per selected scale is the earthing resistance. It is advisable to moisten the ground around the electrodes. It is also important to place all 3 electrodes (i.e. eth, p1, c1) approximately in a line. 4.3

Insulation resistance Test Setting:

1.

Short the AC I/P terminals

(i) (ii) 2.

For single phase : phase and neutral. For three phase : Three phases

Short the DC out put terminals i.e. ve & ve. Test 1. Shorted I/P terminals to earth

(a) (b)

Connect one end of insulation tester to AC input and the other end to earth terminal. Press the AC or (if used ) manually and operate the megger & record the readings. Test 2. Shorted output terminal to earth.

(a) (b)

Connect one end of insulation tester lead to DC output terminal and the other end to earth terminal. Operate the megger and record the reading. Test 3. Shorted Input to shorted output terminals:

(a) (b)

Connect insulation tester between shorted input and shorted output terminals. Operate the megger and record the reading.

Limit: Insulation resistance shall be better then 2 M-, 1 M , & 5 M  for test 1,2, & 3 respectively . 4.4 Power Factor Record the reading of power factor using power factor meter at nominal I/P, max. output, load 25% to 100% . Limit : PF shall be better then 0.95 lagging in above condition . 4.5 (i) (ii) (iii) (iv)

Psophometric Noise Connect the psophometer probes to out put terminals ve and ve. Check the calibration of psophometer . Select the psophometer in weighted mode Record the psophometric value at 100% load at nominal I/P 400 v/230.

Limit : Psophometric noise without battery be less then 4 mv. and 2 mv with rated capacity battery floated across the output.

4.6

Meter Calibration

4.6.1

DC Voltmeter

4 5 6 7 8 9

Set the SMPS unit in Auto Float Mode. Set the O/P voltage with the help of potentiometer -48V, -50V, -56V. Record the same with standard meter reading. Now set the SMPS unit to Manual Boost Mode. Adjust the output voltage by potentiometer or preset to -60V, 65V. Record the same with standard meter reading. Limit: Max, difference shall be 1.5% of full scale reading

4.6.2

DC Ammeter

(i)

Instrument required: Secondary standard DC mV calibrator. Set meter voltage corresponding to millivolt drop at 15, 30, 45, 60, & 75 (units in millivolt)

(ii)

Record the secondary standard meter reading . Limit: difference shall be within 1% of full scale reading.

4.6.3

AC Volt meter:

(i)

Set the meter at nominal A/C I/P voltage .

(ii) Record the secondary standard meter (tong tester) reading . Limit: Difference shall be within 1.5% of full scale reading. 4.7 Efficiency: (i)

Record the input power, out put voltage and current at nominal input and full rated load.

(ii) Calculate the % efficiency as below: (DC O/P voltage X DC O/P current)

----------------------------------------------- X 100 I/P power 4.8 Load sharing Balanced condition :

Connect all FR/BC in parallel in Auto float mode . Switch ‘ON’ the FR/BC at nominal I/P. Set the output voltage to -52.8 V for conventional lead acid battery & - 54 V f or VRLA battery by adjusting the voltage adjustment pre-set. Connect 50% load (of rated capacity of module) to the system. Switch 'ON' 1st module, and observe sharing of load. (vi) Switch 'ON' 2nd module observe load share equally. (vii) Similarly switch 'ON' all other equipped modules one by one correspondingly load is also increased to 100% capacity of the system. (viii) Record the out put voltage and output current of all the FR/BC’s. All the modules share the load equally.

Limit: Load sharing deviation should be + 5A. (ix)

Calculate % unbalance by following formula:

Imbalance in load % Unbalance  -------------------------- X 100 rated capacity 4.9 Load Limiting (Voltage Droop) In Auto Float/Charge mode (A) Disable ATM (Auto trickle mode) (B) Switch ON the unit in Auto Float Mode. At output vol tage54 V (a) (b) (c) (d)

Adjust the output voltage at 54 V. Set the load limiting at 80%. Switch ‘ON’ the unit at 50% load. Gradually increase the load till voltage Droop takes place note down the load current ........ Amp. (shall be nearly 80% of load value.)

(e)

Now change the setting of load limiting to 110%.

(f)

Switch ‘ON’ the unit at 90% load.

(g)

Gradually increase the load till voltage droop takes place Note down the reading of load current Amp. (shall be nearly 110%).

Similarly voltage droop test is repeated for output voltage 56V by repeating the steps (a) to (g). 4.10Voltage Settability

Auto Float Mode (i)

Disable ATM

(ii)

Switch ‘ON’ the system at nominal I/P voltage adjust the output voltage by adjusting potentiometer/ preset to 52.8 V for conventional battery and 54 V for VRLA battery.

(iii)

With the help of voltage adjustment potentiometer adjust the output voltage to -48 V to -56 V.

(iv) Observation: output voltage settability gets adjusted/does not gets adjusted.

(B)

Auto Charge Mode

(i)

Disable the ATM as above

(ii)

Connect all the required meters across proper terminals.

(iii)

Switch “ON” the system at nominal input of 230V for single phase/400V for 3 phase. Adjust

the output voltage adjustment potentiometer/preset to 55.2V for both conventional lead acid and VRLA battery. (iv) Repeat the steps (A) (iii) & (iv) as above . (C)

Manual boost Mode

(i)

Switch over the unit to Manual Boost Mode and adjust output voltage adjustment potentiometer/preset to 65V. With the help of voltage adjustment potentiometer adjust the Output voltage between -56 V to -65V.

Observation : Output voltage gets adjusted/not adjusted. 4.11

Load Regulation

(A)

At Auto Float Mode

(i)

Switch ‘ON’ the equipment in Auto Float mode at 25% load, nominal I/P.

(ii)

Record the power factor, output voltage, output current.

(iii)

Load the equipment to 50% of its rated capacity & repeat record of parameter as at (ii).

(iv)

Load the equipment to 100% of its rated capacity and repeat the record of parameters as at

(ii).

(B)

Manual Boost Mode (i)

Repeat all the test (I) to (iv) for Manual Boost Mode at 25%, 50%, & 100%

Load. Check power factor, output voltage should not vary. 4.12

Test for Mode Change Over

(A)

Start Mode Test

(i)

Battery path Current below 1% of Trickle Charge Current (a) Set Battery path voltage 44V using Battery or otherwise.

(b) (c)

Switch on the unit at nominal input voltage & observe for Mode in which it starts . Repeat (b) for the battery path Voltage 52.8V, 54V & 55.2V. Observation :In all these cases the unit shall start in Float mode and remain in Float mode only.

(ii) Battery Path current above Trickle Charge Current (a) Repeat (a) as above . (b) (c) (d)

Increase the battery path current more than trickle charge value. Switch ON the unit & observe for Mode in which it starts. Repeat

4.13

Heat Run Test

(i)

Place the thermometers in close with surface of all the possible heat generating equipment.

Limit: Maximum temperature limit of transformer and chockes is 70C and for transistors/diode/FET etc 60C.

If it is not possible to place the thermometer in close with heat generating equipment hang thermometer inside the module at a suitable place and observe module inside temperature.

Limit: Module inside ambient temperature is equal to not more than 10C above room ambient temperature. (ii) (iii)

Put the unit (under test) on 100% load at float voltage i.e. - 54V. Record the temperatures for first five hours hourly last three hours with a duration of 30 minutes. Limit: No abnormality shall be observed. Temperature rise in all the case shall be within limits.

4.14 Protection devices and fuse rating Check the protection devices provided and rating of all fuses being used in the equipment. 4.15

Alarms

(A)

FR/BC fail (i)

(ii)

Create a fault condition in any of FR/BC. Check for tripping of unit at I/P and audio and visual alarm and fault indication lamp ‘ON’ corresponding to FR/BC at the switching/control unit.

(B) (i)

(b)

DC Over Voltage (i.e. rectifier O/P over voltage) In Auto Float Charge Mode (a) Switch ‘ON‘ the unit at 25% load of rated capacity . Set the load limit to 110%.

(c) (d)

Increase the output voltage to 56.15 V . Increase the load gradually to 105% .

(e)

Observation : No alarm shall take place. Increase the O/P voltage further slowly and note down the voltage at which the unit shut down and load transferred to battery . This shall be 56.5  0.25 V for 10 ms & creating audio/ visual alarm.

(ii)

In Manual Boost Mode Procedure is same except the cut-off & load values ( use these values as given in spec.)

(iii)

On FR/BC Module Same as above for (I) & (ii)

(C)

DC Under voltage

(i) (a) (b)

In Auto Float Mode Switch on unit at 25% of rated load Set the out put voltage to 43.45 V for VRLA batteries or 44.65 V for conventional lead acid batteries. Decrease the output voltage slowly & note the voltage at which the battery is

(c)

isolated (shall be 43.2  0.25 V for VRLA and 44.4  0.25V conventional lead acid battery, creating audio/visual alarm. Increase the output voltage slowly till the battery reconnects (voltage shall be 44.4  0.25 V

(d)

for VRLA & 45.6  0.25 V for conventional lead acid battery. (e)

Check the extension of audio/visual alarm and tripping of float charger.

(ii)

In Manual Boost Mode Procedure is same except the cut-off and load values (as per specn)

(D)

Mains fail

(i) (ii)

Fail the mains I/P power & observe. Audio & visual alarm created.

(E)

Mains ON battery Discharge

(i)

Switch ‘ON’ unit at nominal A/C I/P.

(ii) (iii) (iv) (v)

Set the output voltage to 52.8 V. Set battery path voltage 52.8 V Start decreasing battery path voltage & observe Mains ‘ON’ battery discharge Audio/visual alarm created. (vi) Start increasing the battery path voltage & observe.

(vii)

Alarm shall stop now.

(F)

System FR/BC over load (voltage drop) Perform the test as described for voltage droop.

(i) (ii) (G)

In the event of voltage droop observe Audio/visual alarm generated. Fan fails (i) Remove the rectifier (SMR) unit & isolate the DC supply of cooling fan.

(ii) Replace the rectifier unit. (iii) Switch ‘ON’ the unit & observe. (iv) Audio/visual alarm generated. 4.16

Function of SMPS Power Plant on E/A.

Switch 'OOF' the AC mains supply. Shift the change over switch to E/A supply so that when E/A starts its output is connected to SMPS Power plant. Start the E/A set put 'ON' the MCB's of all three phases. Connect the full load gradually for some time. Observe all parameters of SMPS power plant. After satisfactory operation, disconnect the E/A supply and normal all the switches.

END