APC 6739380EN/JC Output voltage quality and continuity, Frequency converters without redundancy

Introduction (cont.)

Frequency converters without redundancy

◗ in the event of a shutdown, the load

is no longer supplied with power;

◗ in the event of a major transient

overload (greater than 160% of the

rated load), the inverters will current

limit to 160% of their rated current for 1

second before stopping;

◗ in the event of a small but extended

overload (i.e. a continuous level of

power exceeding the full rated load),

the inverters will continue to supply

power for a period depending on the

magnitude of the overload (10 minutes

Frequency converters with redundancy

◗the shutdown of one unit is of no consequence for the load. The other lines each take up an equal amount of load power and the load continues to be supplied normally;

Inverter shutdown results in the following on the control panel of the concerned unit:

◗ green "load protected" light 5 off,

◗buzzer 1 on,

◗red "load not protected" light 2 on.

◗in the event of an overload, the system only loses its redundancy as long as the overload is less than the total rated power of the functioning units. If the overload is greater, the operating mode is that previously described for systems without redundancy.

for a 125% overload, 1 minute for a

150% overload, see figure 17), and

then stop;

◗ in all three of the above cases,

inverter shutdown results in the

following on the control panel of the

concerned unit:

◗ green "load protected" light 5 off,

◗buzzer 1 on,

◗red "load not protected" light 2 on.

Overload curve
	I
1,5	In
1,35	In
1,25	In
1,15	In
1,10	In
1,05	In
	In
	1	2	3	4	5	6	7	8	9	10	30	120	t (minutes)

Fig. 17

Output voltage quality and continuity

The output voltage is stable in amplitude and frequency and is free of interruptions or transients outside specified tolerances, irrespective of Mains 1 or load disturbances (outages, load step changes, etc.).

Steady state voltage regulation: For stable or slowly varying load conditions, the inverter output voltage is regulated to within +/-0.5% in amplitude.

The frequency of the output voltage can theoretically be regulated to within

0.1% of the rated value, however the output frequency range may be intentionally extended to a maximum of +/-2Hz so that the inverter can remain synchronized with Mains 2 and its inherent frequency fluctuations, thus enabling transfer of the load to the bypass line at any time.

Note:

The output frequency range can be personalized and if necessary modified on the customer site by a qualified support technician from +/-0.25Hz

to +/-2Hz in 0.25Hz steps.

When the Mains 2 voltage moves outside this frequency range, the inverter is desynchronized and operates in "free running" mode, with the output frequency regulated to a high level of accuracy by a quartz oscillator.

When the Mains 2 frequency returns to within the specified tolerances, the inverter is gradually re-synchronized to the bypass line at a rate of 0.5Hz to 2Hz/s (as per the value personalized by the after-sales support department), thus avoiding exposing the load to sudden frequency variations.

Transient voltage regulation: The inverter output voltage is not notably affected by instantaneous major variations in load characteristics. This is due to the PWM (Pulse Width Modulation) chopping technique and the microprocessor-based regulation system that instantly compensates for any variation. In particular, the inverter output voltage remains within +/-5% of the rated voltage for load step changes of 25 to 100% or of 100 to 25%.

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