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Understanding Isc and Imp

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When matching a Tigo TS4 with a solar module, it is important to know that the TS4's short-circuit current (Isc) and current at maximum power (Imp) specifications must be higher than the maximum Isc and Imp that the PV module can produce (even in cold conditions).

  • Isc (current at short circuit) - The amperage a solar module produces when its positive and negative leads are connected together (shorted). As a rating, it is the maximum current the module can create.

  • Imp (current at maximum power) – The amperage a solar module can produce at its ideal voltage. This happens when the module is connected to a load source (like an inverter or charge controller).

To understand the relationship between Isc and Imp, let's take a look at an IV curve (a common graph used to evaluate solar module performance). It shows the module’s power output and how it changes based on current and voltage.

A diagram of a voltage Description automatically generated

The module’s Isc is a fixed value at short circuit. When a load is placed on the circuit (by the inverter or charge controller), the voltage and current adjust until the MPPT (maximum power point) between the Imp and Vmp (voltage at maximum power) has been achieved. At this point, the module’s designated power target has been achieved. 

If the PV Module's Isc or Imp remains higher than the TS4's specs for Isc, the MLPE could experience sustained current damage, which can lead to an Overcurrent shutdown (to avoid a thermal event).

 

Comparing Datasheets

Tigo's modern TS4 Flex MLPs are sold in 500W and 700W versions.

  • TS4 500W: Imp = 15A. Max Isc = 20A.
    Manufactured for use with most solar modules on the market.

  • TS4 700W: Imp = 20A. Max Isc = 25A.
    Manufactured for use with larger, more powerful PV Modules  

Before selecting which model to use on your system, please refer to the TS4 datasheets for the Imp and Isc electrical specifications of the model you are interested in. Make sure that the PV Module you are selecting does not exceed the Isc (or the Voc) of the TS4, even in cold conditions (-0°C).


Example: (from TS4 500W Datasheet)

 

 

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