Phoenix Contact SCK-M-U-1500V Handleiding (128 Pagina's)

Handleiding

SOLARCHECK string voltage measurement with SCK-M-U-1500V

105608_en_02 PHOENIX CONTACT 27

Calculation basis for Table 4-1 and Table 4-2:

The maximum measured value deviation of 1% (of the measuring range final value) is based

on the 100 V DC to 1500 V DC system voltage range. The deviation may be greater below

100 V DC.

4.1.2 Parallel connection of multiple voltage measuring devices

in a system

Due to the circuit architecture in the device, the voltage measuring input is connected to

ground via the internal impedances. Resistance Rx is 20 MΩ respectively. If multiple volt-

age measuring devices are connected to the same generator in parallel, these impedances

are also connected in parallel. This results in an overall reduced impedance of the generator

to ground. This can affect the response of any ground fault detection in the system.

The impedances of the voltage measuring devices used within a generator (per inverter in-

put) therefore have to be taken into consideration when defining the threshold values for

ground fault detection.

The following impedances result depending on the number of voltage measurements con-

nected in parallel in a system.

If:

(0 < U+ < 1500 V) and

(0 < U- < -1500 V) and

(0 < Difference (U+, U-) < 1500 V

Then

Analog OUT:

Difference (U+, U-) x 8 V

+ 2 V

1500 V

Table 4-3 Impedances

Number of parallel

voltage measurements

Individual impedance (+  PE) Total impedance (+  PE)

1 20 MΩ 20 MΩ

2 20 MΩ 10 MΩ

4 20 MΩ 5 MΩ

8 20 MΩ 2.5 MΩ

16 20 MΩ 1.25 MΩ

32 20 MΩ 0.625 MΩ

64 20 MΩ 0.313 MΩ

128 20 MΩ 0.156 MΩ

…

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