MasterGuard MG-CO/2000 Manuel de service télécharger pdf (Page 10)

6 Control Unit, IGBT Inverter

MASTERGUARD Series SIII

UPS Systems from 60 to 800 kVA

MKA4CAT0UKSIII/Rev. 11-11/2004/UK

6.4 Total Harmonic Distortion

The inverter shall provide harmonic

neutralisation and filtering to limit the

THD to on the voltage to less than 3%

with a linear load. For reference non-

linear load (as defined by EN62040-3)

the THD shall be limited to less than 5%.

6.5 Neutral sizing

The sizing of the inverter neutral shall

be oversized on all ratings in order to

cope with the combination of

harmonics on the neutral wire when

driving single-phase reference non-

linear loads. From 60 to 200kVA the

inverter neutral is sized x 1.7 in relation

to the phase, while from 250 to

500kVA it is x 1.4 in relation to the

phase. Further oversizing could be

provided on demand.

6.6 Output power transformer

A dry type isolation transformer shall

be provided for the inverter AC output.

The transformer shall have an

insulation class H+. The temperature

limit of the insulation class of the

material shall not be exceeded when

operating at full load and within

ambient temperature limits.

6.7 Overload

The inverter shall be capable of

supplying an overload of 125% for 10

minutes and 150% for one minute of

the nominal power.

6.8 Inverter shutdown

In the event of an internal failure the

inverter shall be immediately

disconnected from the critical load and

shut down by the control unit. The UPS

device or the parallel-operated UPS

systems shall continue to supply the

load from the reserve supply without

interruption, if it is within permissible

limits.

6.9 Output voltage symmetry

The inverter shall guarantee the

symmetry of the output voltages at

±1% for balanced loads and ±3% for

100% unbalanced loads.

6.10 Phase displacement

The phase angle displacement

between the three-phase voltages

shall be:

•120°±1°for balanced loads

•120° ± 2° for unbalanced loads

(0, 0, 100%)

6.11 Short Circuit

The inverter short circuit capacity of

Series S

III for the first 10ms shall be

>200% for any short circuit

configuration. After the first 10ms, it

shall limit the current to >150% for 5s,

then it shall shut down.

6.12 Automatic upgrade of inverter

rated power

The inverter shall automatically

upgrade its power as a function of

ambient and operating temperatures,

as shown in Figure 5. In the most

common conditions (25°C) Series S

III

shall provide 10% more power than

nominal. In these conditions the

battery charge will be reduced

correspondingly.

For example:

@40°C, Idc tot. = 0.75(Idc inv) + 0.25

(Ibatt)

@25°C, Idc tot. = 0.83(Idc inv) + 0.17

(Ibatt)

6.1 AC voltage generation

From the DC voltage of the intermediate

circuit the inverter shall generate

sinusoidal AC voltage for the user load

on the basis of pulse-width modulation.

By means of the digital signal processor

of the control unit the inverter IGBTs

shall be controlled so that DC voltage is

divided up into pulsed voltage packets.

A transformer shall be provided at the

output of the inverter. Through this

transformer and a low-pass filter the

pulse-width modulated signal shall be

converted into sinusoidal AC voltage.

6.2 Voltage regulation

The inverter output voltage on the

three phases shall be individually

controlled to achieve the following

performances:

6.2.1 Steady state

The inverter steady state output

voltage shall not deviate by more than

±1% in a steady state condition for

input voltage and load variations within

the quoted limits.

6.2.2 Voltage transient response

The inverter transient voltage shall not

exceed Class 1 limits when subjected

to application or removal of 100% load

as defined by EN62040-3.

6.3 Frequency regulation

The inverter output frequency shall be

controlled to achieve the following

performances:

6.3.1 Steady state

The inverter steady-state output

frequency, when synchronised to

reserve supply, shall not deviate by

more than ±0.75% adjustable to

±1.5%, ±2.5%, ±6%.

6.3.2 Frequency slew rate

The frequency slew rate shall be ≤ 1Hz

per second.

6.3.3 Frequency Control

The output frequency of the inverter

shall be controlled by a quartz

oscillator which can be operated as a

free running unit or as a slave for

synchronised operation with a

separate AC source. The accuracy of

the frequency control shall be ±0.05%

when free-running.

Figure 5. Automatic power upgrade

15 25 30 40

115

112

110

105

100

Output Power

Ambient

Temperature

Tecnico-SIII-MG 10-11-2004 8:22 Pagina 8

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