General description

On some charger installations the available power for charging depends on the overall main fuse load. In installation like an apartment complex the apartments must have power priority, while car-charging uses the excess power available. Since this excess power changes dynamically, this must be monitored, and communicated to the ZapCloud load-balancer to ensure that the main fuse is never overloaded due to car charging.
This document describes the main fuse current measurement solution.


The Wago PLC 750-8101 is a rail-mounted modular solution. With the 3-phase 750-495 measurement module the unit can perform advanced 3-phase voltage and current measurements. In addition the 750-600 block is required as an end module to terminate the module block.
This PLC is connected to Internet with standard RJ45 Ethernet plug. A second Ethernet plug can be used for directly connecting a maintenance computer or for extending the Ethernet connection to other permanent equipment.


For a complete 3-phase voltage and current measurement setup and 4 current sensor coils should be used. The 4th current sensor measuring on the Neutral wire is not used on installations with IT-grid and is optional for for TN-grid.
The voltage measurement are provided internally. The Rogowski coil sensors have a measurement range from 0-4000A. Due to increased uncertainty in the lower region, they should not be used for installations with max fuse less than 160 A.

Considerations during installation

  • The installation point requires Internet access through an Ethernet connection. By default the unit is configured with dynamically assigned IP-address. If necessary, a static IP-address can be configured.
  • The installation point must have sufficient space to place the IP67 Boks.
  • The installation point must allow attaching the current sensor coils around the individual wires L1, L2, L3 and N. Coil dimensions must be suitable for the installation point cable dimensions, and max sensor current rating must be larger than max main fuse current. If the main fuse is overloaded, the sensor must be able to measure the overload current. This is vital for performing diagnostics in case of overload.

The ID(Ethernet MAC address) of the PLC must be associated with the correct installation in ZapCloud. This information must be communicated to Zaptec support or configured under the Installation on the Zaptec portal web page(


How to activate

  • Install the Wago Apm 
  • For the 0-160A version, make sure the 4 orange switches marked L1, L2, L3 and N are in position 1 (connected)


  • Check that the grey switch on the Wago Apm is set to "Run"


  • Turn the power on.
  • Observe that the diode marked "USR" is blinking green. The Apm is now communicating with the Zapcloud.
    • If "USR" is blinking orange, the unit is trying to make contact with Zapcloud. Check the internet connection
    • If "USR" is blinking red, the unit has been online previously but is currently unable to contact the Zapcloud.
  • The unit needs to be activated in the Zaptec Portal. This is done under installation -> Settings-> Power management -> APM
    • Enter the Wago ID (XX:XX:XX:XX:XX:XX). This can be found on a sticker on the Wago unit.
    • Set the main circuit breaker value.
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