Beckhoff EL3773, Documentation

Page: 103 / 179

Commissioning
EL3773 103 Version: 2.5
Fig. 111: Power measurement at a machine
Note
Negative power values
If negative power values are measured on a circuit, please check whether the associated
current transformer circuit is connected correctly.
Note
Current measurement
A current measurement requires a voltage source to be connected. A current measurement
is not possible without voltage source.
Power measurement on motor with 2 current transformers
• The voltage is measured via the connections L1, L2 and L3.
• The current is measured with two current transformers [
}
123] via the connections I
L1
and I
L2
.
• The sum of all currents in the 3-phase mains network is 0. The value in circuit I
L3
can be obtained
accordingly by wiring the EL3773.
WARNING
WARNING: Risk of electric shock!
If you do not connect terminal point N with the neutral conductor of your mains supply, you
have to earth terminal point N, in order to avoid dangerous overvoltages in the event of a
fault with a current transformer!
Attention
Attention! Risk of device damage!
Avoid confusing the current and voltage circuit during connection, since the direct connec-
tion of mains voltage to the terminal points for the current transformers (typical input resis-
tance 220 mΩ) would destroy the power measurement terminal!