Each PSU output is electronically fused, with the limit adjustable in 5-ampere steps up to a maximum of 25 amperes. What sounds like a convenience feature is actually the circuit's main protection – and it follows the same rules as a fuse, but without tools.
What electronic fusing means
A fuse protects by blowing. It is then used up, and its trip behavior is determined by its design. Electronic fusing measures the current and switches off. It is then available again, and its threshold is adjustable.
The important difference for planning: with the PSU, the additional fuse per output is eliminated. What would otherwise be a fuse in a holder is here a numerical value in the configuration. This completely changes the operation – but not the question of what value is correct.
The basic rule: the cable, not the device
This rule remains unchanged. The fusing protects the cable from carrying so much current in the event of a fault that it overheats. It does not protect the connected device – which either comes with its own protection or has none.
This results in the order in which the value is determined:
- Determine the consumer's operating current – from the datasheet, not estimated.
- Check starting behavior. Motors and compressors draw significantly more current when starting.
- Determine the cable's cross-section and its current carrying capacity – depending on length, bundling, and ambient temperature.
- Select threshold: above the starting current, below the cable's carrying capacity.
If no value fits between the two limits, it is not the threshold that is wrong, but the cross-section that is too small. Raising the fusing to avoid tripping reverses the protection entirely.
Using the 5 A grid
The threshold can be set in 5 A steps: 5, 10, 15, 20, 25 A. This is coarser than a freely selectable number and finer than the usual range of fuse holders in the expansion.
Practically, this means: You choose the nearest value above the starting current and check whether the cable can handle it. A consumer with 7 A continuous current and short peaks up to 11 A gets 15 A – provided the cable is designed for it.
WarningThe adjustable threshold tempts one to simply increase it if a fuse trips. This is precisely the point at which the protection loses its purpose. A repeatedly tripping fuse indicates a fault; it is not the fault itself.
The real advantage: Changes without modifications
The biggest practical gain is not in installation, but afterwards. If a consumer is replaced with a more powerful one, the adjustment is a setting instead of a fuse change. If a channel is re-assigned, the same applies.
The point that remains: the cable does not change. If you increase a channel from 10 to 20 A, you must check whether the installed cable can handle it – otherwise, you have configured a weakening of the system via software that you no longer see in any fuse.
Battery protection per output
In addition to current limiting, each output offers individual battery protection, either time-controlled or voltage-controlled. This is a different function and is often confused with fusing.
The current limiting protects the cable from too much current. Battery protection protects the battery from being drained by a consumer. It is useful where a consumer runs unattended – and it should be prioritized: convenience consumers switch off earlier than those that are really needed.
Typical errors
- Designed according to the device instead of the cable. The fuse protects the cable, not the consumer.
- Threshold raised because it trips. This removes the protection, but not the problem.
- Starting current ignored. Leads to trips exactly when switched on.
- Channel reassigned without cable check. The new value fits the consumer, but perhaps not the installed cross-section.
- Battery protection set the same for all channels. Then everything switches off simultaneously at the critical moment, instead of in stages.
