1. Ups Choice Criteria

UPS RT2000 SERIES

INTRODUCTION

1. UPS CHOICE CRITERIA

1.1.   OVERVIEW

The disturbance which electric power distribution networks are normally subject to, impose the choice of corrective systems that will ensure an absolute continuity and stability in the power supply of particularly important loads.

A fast accurate choice may be determinant both in avoiding relevant economic loss in industrial production enviroments as well as in safeguarding human lives in hospitals. These, are only two of the most immediate examples.

There are many more sectors in our everyday lives where these precautions must be given thorough consideraction, some examples:

·  Air traffic control systems and runway lights

·  EDP centres

·  Telecommunications systems

·  Hospitals

·  Pumping systems

·  Industrial processing plants

·  Auxiliary circuits for electric plants

·  Tunnel illumination, etc.

At the moments UPSs are the easiest and most efficient systems to guarantee power supply continuity, stability and cleansing of mains disturbances.

1.2.   TYPES

The following solutions are normally proposed:

·  UPS Off Line. Loads are normally fed from mains; when the required power is not within given tollerances, loads are fed by the inverter which draws power from the batteries. Apart from requiring a considerable switching time from mains to inverter, this solution also requires the adoption of auxiliary devices if complete mains disturbance cleansing is requested.

·  UPS Line Interactive. Loads are normally fed with stabilized power thanks to a parallel connection of supply input and inverter output. When the AC input power is not within acceptable tollerances, the loads are fed by the inverter with an autonomy wich depends on the energy stored by the batteries or, until the input power returns within acceptable limits. While this solution offers an almost inexistant intervention time on the part of the inverter, it requires particular attention in input in order to eliminate mains disturbances and the dangerous transients also cuased by the ains in case of sudden interruption.

·  UPS On Line. Loads are normally fed by the inverter. When the AC input power exceeds acceptable tollerances, the loads are fed by the battery/inverter system with an autonomy which depends on the energy stored by the batteries or, until the required power returns within acceptable limits, This solution offers zero inverter-mains switching times if paired with a static switch and a perfect loads power stabilization due to the fact that the inverter is the preferential power supply. If also offers complete cleansing of mains disturbances.

1.3.   TYPES CHOSEN BY RAMET

ON LINE

The On Line configuration is the only taken into consideration by RAMET at the moment as it is quite obviously the one that offers the best performances and guarantees.

SINUSOIDAL Wave Shape

The inverter suggested by RAMET supplies sinusoidal wave shape for the whole RT2000 UPS family.

Today, it is possible to find the most varied proposals (“square” wave shape, “trapezoid”, “pseudosinusoidal”, “step-wave”); it is therefore important to keep in mind that the only suitable shape for the supply of any kind of load is the sinusoidal one.

Manual BY - PASS

All RT2000 family UPSs are equipped with a manually activatable By-pass, essential in order to carry out system maintenance and repair jobs without interrupting power to the loads.

IGBT Semikron Power Modules

All RT2000 UPSs use Skiip to IGBT modules with integrated driver produced by Semikron. Thanks to these devices it is possible to work in PWM with very high frequences, thus obtaining significant in trasformer and inductor volume/wieght and a sensitive reduction of produced acoustic noise.

Dimensioning of IGBT modules is planned in direct collaboraction with Semikron technicians also by using SW developed specifically by them.

Reduced dimensions

As a direct consequence of the above mentioned point and thanks to a rational integration of the different power assemblies and of the control boards, the RT2000 UPS family units can be built with a considerable reduction of mechanical dimensions.

Microprocessor

Visualization of machine status and diagnosis are controlled by a microprocessor and are shown on a LCD display which offers detailed descriptions in five languages, selectable by the user. This, in addition to a synoptic panel with normal state and alarm luminous signals, complete with an acoustic alarm which may be silenced.

1.4.   EVAULATION PARAMETERS

Apparent Power (in VA or kVA)

It is defined as:

PAPP = V x I for monophase load

PAPP = (VL1 x IL1)+(VL2 x IL2)+(VL3 x IL3) for three phase load

where V is the phase voltage to load

I is the absorbed load current under normal load conditions.

The UPS’s Apparent Power is defined for a permanent load in VA of kVA with cosj (power factor) specified with sine wave.

Active Power (in W or kW)

Is defined as:

PATT = PAPP x cosj where cosj is the power factor.

PATT or cosj data is rarely indicated, therefore a correct dimensioning requires measuring of PATT absorbed by loads.

Crest Factor

A linear load absorbs a sinusoidal current which presents a RMS value (IRMS normally measured and declared) and a peak value (IPK).

Crest factor is defined as:

IPK

CF = ¾¾¾¾

IRMS

The normal value for a linear load is CF = 1.41.

Most of the loads applied to UPSs are non linear loads; they absorb distorted currents which present a CF greater than 1.41 and therefore require higher peak current with consequent increase of output distortion with respect to equivalent linear loads. CF Crest Factor value is never indicated in practice and may require specific measures. RAMET RT2000 family UPSs meet EN50091-1 norm, attachement M5, which defines a typical non linear load with CF=3. RT2000 UPSs adopt distinct current sensor on each phase and are therefore able to consider the phase current “true RMS value”. More economic and surely less reliable systems take the average current value into consideraction thus offering a less accurate regulation.

Overload

Overloads are temporar requests from load which exceed absorption under permanent working conditions. They are caused by current peaks which can occur during start up of one or more loads. RAMET RT2000 family UPSs are able to offer high overload capacity under normal working conditions (“On Line”) and, in case of overload greater than value or time admissible by the inverter, they guarantee the automatic switching to emergency mains in zero time.

Parametric functioning conditions

In dimensioning a UPS unit it is necessary to take following parametric functioning conditions into consideration:

PAPP The UPS nominal Apparent Power must be equal or greater than load PAPP.

PATT The UPS nominal Active Power must be equal or greater than total load PATT.

CF It is necessary to verify that the UPS unit is dimensioned to feed non linear loads with CF equal or greater than that of all the loads together and that the corresponding output distortion power is compatible with the loads to be fed.

Future Expansions

While dimensioning a UPS, it is a good idea to forsee a certain power margin for possible future expansions. Generally a power margin equal to 30% is taken into consideration.

Efficency

The efficency (h) is the ratio between output Active Power and input Active Power of the UPS.

PATT O

h  = ______

PATT I

RAMET RT2000 family UPS units have efficency included between 0,898 (89,8%) and 0,926 (92,6%) for a load equal to 75%. For other load percentages please refer to “technical characteristics”, pages 15 and 17.

Noise

The placement of the UPS unit in a given enviroment must occur so as not to alter normal life conditions. It is therefore necessary that average acoustic level bemeasured according to ISO 3746 norm be equal to:

·  52 dBA for an office

·  60 dBA for an EDP room

·  65/75 dBA for an electrical instruments room

RAMET RT2000 family UPS units are conceived to be installed in EDP rooms for power up to 30kVA and in electrical rooms for greater powers. The considerable reduction of the level of acoustic noise which can be seen in the above mentioned values is largerly reconductable to the fact that it is possible to work with very high frequencies, thanks to the use of previously mentioned IGBT Semikron modules.

Protection degree

It is intended as defined in CEI EN 60529 norm “Degree of protection of housings (Code IP)” against access of dangerous parts and against the entrance of solid bodies, (first characteristics number and possible additional letter) and against the entrance of water (second characteristics number and possible supplementary letter).

RAMET RT2000 family UPS units offer IP20 protection degree even with front door open.

Reliability

RAMET UPSs are designed and built in conformity with ruling norms (89/392/CEE Machine Directive). Large security margins are forseen with regards to expected power values, assembly sturdiness, personal operator safety, reliability of the component suppliers of which we would like to mention: AEG, Semikron, Motorola, ST, Analog Device, Ziehl-Ebm, Siemens, Legrand, Ferraz. All RAMET UPSs undergo careful testing and a 24 hours burn-in.

Battery Autonomy

Many and varied are the solutions regarding accumulator batteries to pair with the UPS. Depending on the enviroments and power to be used, different types of batteries and housings may be suggested.

First and foremost RAMET takes into consideration the reliability, safety, solidity and maintainability of the RT2000 family UPS units and has therefore chosen to always place the batteries in a proper casing next to the actual UPS. “Maintenance Free” lead type batteries are normally suggested and also VRLA when enviroment conditions make it necessary. In case an appropriate (CEI 21-6) battery room is available, Open Vase Stationary Batteries or other solutions may be used.

Considerations on the misleading concept of typical autonomy.

In the definition of autonomy, “typical autonomy” is often used which has nothing to do with the real autonomy based on the charge value at 100%, expressed in W of kW.

It is always preferable to refer to the full charge autonomy.

1.5.   COMMUNICATION

Communication scope

Signals normally available for user can be of local or remote type and must meet the following requirements:

·  Monitoring of UPS and emergency mains status

·  Diagnostics during normal or critical working conditions

·  Functional alarms and signals for Shut-down requests to loads

Local communication

·  ALPHANUMERIC DISPLAY: the signals panel of RT2000 family is completely managed by a microprocessor able to visualize above mentioned messages by way of an intelligent alphanumeric display. The user may select desired language between Italian, English, French, German, Spanish.

·  LIGHT INDICATORS: on the same signals panel, the microprocessor controls some light signals (LED) included in a mimic panel and is able to immediately visualize the UPS working conditions, the correct presence of emergency mains, the battery status and the load feeding conditions,

·  DIAGNOSTICS ON CONTROL BOARDS: all the electronic boards placed on the upper internal door of the UPS are equipped with some LEDs for normal conditions and anomalies signals.

Remote communication

REMOTE REPORT BY WAY OF CURRENT FREE CONTACTS: if the UPS is not easily accessible by the user, a remote signal for alarm and diagnosis of the principal functioning conditions (at least “general alarm” and “battery discharging”) can be forseen. The RT2000 family can send different signals to a sinoptic supplied with the UPS, even with remote repetition of alphanumeric display.

1.6.   OPTIONS

RT2000 family can be enriched by various optionals customizations which make it even more respondent to customer’s specific needs; some of these have already been mentioned in the previous paragraphs, other are described below:

·  Galvanic separation transformer: the standard version is equipped without a galvanic separation transformer within the chain, thus maintaining neutral regime between input and output unaltered. If it should become necessary to modify the neutral regime below the UPS, a galvanic separation transformer will be forseen with a specific housing to be added to the UPS chain.

·  Dodecaphase rectifier: if a dastric reduction of input current harmonics should be required, the rectifier can be coupled and fed by a transformer with double output so that the combinations of current to the primary causes a cancellation of the most harmful harmonics.

·  Redundant parallel system: on all the RT2000 family it is possible to forsee a parallel with automatic power sharing up to six UPS units.

·  Emergency interrupt button: it can also be placed in a remote position and, in case of emergency, it looks after interrupting of all powered parts of the UPS as well as the automatic sectioning of the battery. The presence of this device imposes the adoption of an automatic battery braker in substitution of the manual braker forseen in the standard version.

·  Separate input for by-pass source

·  Remote mimic panel

·  Load distribution panels

2.  UPS RT2000 SERIES INTRODUCTION

2.1 GENERAL DESCRIPTION

Fig. 2.1.1 shows the configuration of RT2000 series.

fig. 2.1.1

RECT. = RECTIFIER INV. = INVERTER

BATT. = BATTERY S.S. = STATIC SWICH

IBYM = MANUAL BY - PASS

The purpose of a UPS unit is that of supplying electric power with a high grade of stability with regards to voltage, frequency and reliability. Seeing that under normal working conditions the load is prevalently fed through the inverter, such a UPS is called ON-LINE (fig. 2.1.2)

fig. 2.1.2

Under normal conditions the RECTIFIER feeds both INVERTER and BATTERY. In case of mains failure the battery would start feeding the load through the inverter for a time depending on battery dimensions, unless normal mains conditions are reset before. (fig. 2.1.3)

fig. 2.1.3

If the INVERTER should break down or if the energy required by the load should exeed that supplied by the UPS, in “zero time” the static switch switches the load onto the emergency mains thus guaranteeing a continuous feed. (fig. 2.1.4)

fig. 2.1.4

As soon as the conditions go back to normal, the static switch automatically switches load back onto the inverter.

Manual by-pass is available for maintenance and repair of the UPS without solution of continuity of the load feeding. (fig. 2.1.5)

fig.2.1.5

2.2. RECTIFIER MODULE