The purpose of Zaptec Pro phase and load balancing is to maximize an installations charge throughput, and for three phase networks to balance the load over all phases. All installations that have not been put in stand alone mode will be controlled and balanced by the ZapCloud.
Changes in an installations runtime, e.g. vehicles are connected, current limits change and so on, will trigger the load balancer to run. Any required changes will in turn be sent to the respective chargers. There are many settings that is taken into consideration when resolving the optimal charge configuration for an installation.
Installation network type
We support 3 phase charging on both 400V TN net and 230V IT net (Norway). This setting must match the installations physical configuration. Because of this the setting is only available for users with the Service role.
Note regarding 3 phase charging on IT net. Very few vehicles support this, the chargers are therefore set to default 1phase on 3 phase IT installations. The installation will balance on all three phases, even if the vehicles only receive 1 phase charging.
Installation max current
The max current that can be allocated for charging on all the installations charging stations. This is normally set to match the top circuit breaker. Configuring this higher than the installations physical constraints will result in the main circuit breaker triggering. Because of this the setting is only available for users with the Service role.
Installation 3 to 1 phase switch current
This setting determines when a vehicle should be switched from three phase to single phase charging. The default current is 15A, meaning that if the allocated three phase charge current drops below 15A, the charger will be assigned a single phase instead. For most installations this configuration will provide the best throughput of the whole installation. For installations that have a limited number of charging stations, or a low installation max current (<32A), it may be useful to set this current lower to allow some chargers 3 phase charging. If a TN 3 phase installation should only provide single phase charging, the setting can be set to 32A. The setting can be set by users with either Owner or Service roles.
Circuit max current
An installation consists of a charging system circuit breaker (configured through installation details) and one or more circuits. Circuits are configured through the installations circuit details in ZapCloud Portal. The circuits max current should usually match the physical circuit's circuit breaker, and will limit the current allocated to chargers in the circuit. Because this setting needs to match the physical constraints of the installation, it's only available for users with the Service role.
Charger max current
The max current a charger can be allocated. Can be used together with charger max phases to limit how much power the charging station should provide. This setting is available to users with Owner or Service role for the charger.
Charger max phases
The max number of phases a charger can be allocated (one or three). Can be used together with charger max current to limit how much power the charging station should provide. This setting is available to users with Owner or Service role for the charger.
Charger min current
The lowest current the charger will accept. Balancer will not allocate current to the charger if it drops below this threshold. This setting is available to users with Owner or Service role for the charger.
Charger online status, offline current and phase
If a charger is offline, we do not know whether the charger is active or not. ZapCloud automatically optimize offline current and phase for installations every hour, ensuring that offline chargers can provide as much current as possible without triggering any circuit breakers, in case all chargers in the installation is active at the same time. The offline current and phase setting is sent to the charger when it's online. If a charger goes offline, it will provide current according to the offline settings, and the balancing algorithm will reserve offline currents to prevent circuit breakers from triggering.
In addition to these settings the current status of the installation is also part of the equation:
Depending on installation max and available current, and the number of active chargers, there may not be enough power in an installation to start new charge sessions. Sessions will be queued if there is not enough power, and will be started as soon as other sessions finish. Queued sessions are started in the order they were connected. If sessions needs to be stopped when installation max or available current is decreased, this is also handled by the charge queue. Sessions are started and stopped in a FILO order (First In, Last Out), meaning that the first started session is the last stopped.
Three phase charging not supported by vehicle
If a vehicle is allocated three phases, but does not use more than one phase, it will be relocated to a single phase. This prevents phase 1 being excessively utilized in these scenarios. If a charger has not used more than one phase for the past 5 minutes, it can at any time be moved to a single phase. The charger is only moved when required.
Preferred charge phase
When allocating a single phase to a charger, the charger will prefer its offline phase.
A charger that is allocated a single phase, will keep this phase for as long as possible. If a charger needs to be moved to balance the installation, the last connected charger is moved first.
Chargers that have been offline in a charging session, will be locked to its offline phase for the duration of the session. This will prevent chargers from switching phases when going offline/online. If the charger is locked to a phase with no available power (due to manual or automatic available current setting), it will not provide current until there is available current on the chargers offline phase
Sticky single phase
If a vehicle in an installation supporting three phase charging has for some reason been allocated a single phase, e.g. due to 3 to 1 phase switch current, it will stick to single phase charging for the duration of the session. The reason for this is to limit the number of stop/start commands sent to a charger. We try to limit this as some vehicles abort charge sessions after multiple stop/start cycles.
The applied power management scheme will also be a factor in this. For Zaptec Pro installations, there are three different power management options.
Manual power control
This is the basic power management tool, where the system adheres to the setting: Charging system circuit breaker (A)
Additionally, it is possible to reduce available current on one or more phases. This can be helpful if there are known loads on the same circuit that are not from charging stations.
Scheduled power control
The scheduled power control allows the installation owner or service provider to create a time schedule of the available power of the installation.
For more information, see this article.
Automatic power management (APM)
By installing an APM ( available models might differ between countries), it is possible to balance the load on the installation towards the buildings main fuse or similar.