Inrush current | NETIO products: Smart power sockets controlled over LAN and WiFi
For a brief time after being switched on (several ms), 110/230VAC electrical appliances often draw a significantly (3 to 30x) higher current than in normal operation. This inrush current is different for different device types (LED lightbulbs, heaters, switching power supplies for PC/servers).

For example, a 580W ATX computer power supply (2.5A rated input current) may draw several times more for a few ms after power-up. For the 2.5A rating, the peak consumption may reach 8A to 60A! For details, see e.g. this overview: http://www.tomshardware.com/charts/120v-desktop-power-supplies/Inrush-Current,2565.html?_ga=1.66345518.1078295973.1482763161

 

In the context of NETIO products

When a large load with a high inrush current or several similar devices are switched on at the same time, the maximum current is briefly exceeded. This can trip the circuit breakers (for the room or even for the entire building), which then need to be manually reset.

Neither the NETIO device nor the circuit breakers are able to filter out the inrush current. However, problems caused by inrush current can be limited using delayed (sequential) switching of electrical sockets.

 

Device damage

  • In standard NETIO 4x products, frequent switching of appliances with a high inrush current can damage the internal relay.
  • Some NETIO products feature ZVS (Zero Voltage Switching) or ZCS (Zero Current Switching).
    These products are significantly more resistant against the internal relay damage when controlling appliances with a high inrush current.
  • However, to switch electric motors and other devices with a very large inrush current, we recommend to use appropriate contactors instead of using NETIO sockets directly.

 

Circuit breakers tripping when power is restored 

When power is restored after an outage, circuit breakers may trip when too many appliances with a high inrush current are connected to the given circuit branches.  The Sequential switching function is designed to protect against this circuit breaker tripping when too many devices connected to the sockets are switched on at the same time.

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