Power Measurement On Motor With 2 Or 3 Current Transformers - Beckhoff EL34 Series Documentation

Application examples
7.1 Power measurement on motor with 2 or 3 current
transformers
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! Risk of device damage!
Avoid confusing the current and voltage circuit during connection, since the direct connection of mains volt-
age to the terminal points for the current transformers (typical input resistance 220 mΩ) would destroy the
power measurement terminal!
EL3443
• The voltage is measured via the connections L1, L2 and L3.
• The current is measured with two current transformers [} 29] via the connections I
• The sum of all currents in the 3-phase mains network is 0. The value in circuit I
accordingly by wiring the EL3443.
Fig. 161: EL3443, Power measurement with 2 current transformers on a motor
In the circuit shown above (Fig. EL3443, power measurement with 2 current transformers on a motor),
ensure that the three-phase system is either earth-free or has an earthed star point. Alternatively a
transformer can be included in a Yy0 circuit.
EL3453
• The voltage is measured via the connections L1, L2 and L3.
• The current is measured with three current transformers [} 29] via the connections I
260
WARNING
NOTE
Version: 1.5
and I .
L1 L2
can be obtained
L3
, I .and I
L1 L2 L3
EL34xx