Solarcheck String Voltage Measurement With The Sck-M-U-1500V; Function; Voltage Measurement - Phoenix Contact SCK-C-MODBUS User Manual

4 Solarcheck string voltage measurement with the
SCK-M-U-1500V
105608_en_00

Solarcheck string voltage measurement with the SCK-M-U-1500V

4.1

Function

The Solarcheck voltage measuring module is used to measure PV voltages up to
1500 V DC. Voltage measurement can be performed in isolated systems as well as systems
grounded on the positive or negative side.
The analog output of the device maps the measured system voltage as a 2 ... 10 V signal.
The module is usually connected to the corresponding 8-channel current measuring module
(SCK-M-I-8S-20A, Order No. 2903241).
As an option, the voltage measuring module can also be operated as a simple analog mea-
suring device outside of the Solarcheck device range.
Observe the installation instructions in "Installing the SCK-M-U-1500V voltage measuring
module" on page 57.
4.1.1

Voltage measurement

The voltage is measured via two impedance chains, one of which measures the voltage of
+ to PE and the other the voltage of - to PE. Both measured values are first determined in-
dividually and are then added. This gives the system voltage value. This value is then output
as a 2 ... 10 V analog signal via the analog output.
U
R
1
X
0...1500 V DC
U
R
X 2
Figure 4-1 Block diagram (Rx = 20 MΩ)
Marginal conditions for valid voltage values:
1. U+ ≥ PE ≥ U-
2. 0 < U+ < 1500 V
3. 0 < U- < -1500 V
4. (U+) - (U-) ≤ 1500 V
The difference between U+ and U- must not exceed 1500 V. Negative differential mode volt-
ages are not permitted.
It is imperative that the PE contact is connected, as in addition to its safety-related function
it is also used as the reference potential for measurement.
U_OUT
0 V
P_IN
24 V
PHOENIX CONTACT
25