Question:
How much and how long can a frequency inverter be overloaded?
Answer:
A Lenze frequency inverter can deliver a current of 150 % for 60 seconds. This means that during this period it delivers 50 % more current as in standard operating status. During this overload time the created heat of the device is the limiting element / the energy. In case of 50 % more current in 60 seconds this means.
50 % * 60 s = 3000 %s
This is the maximum energy the inverter can stand.
If the inverter is less overloaded, e. g. with only 30 % more current, the remaining time, the overload may occur, increases, as the maximum energy stays the same. Therefore:
3000 %s / 30 % = 100 s
The inverter may supply an overload of 30 % for maximum 100 s.
An operation of the frequency inverter with overcurrent (in this example for 100 s), requires unloading with the same energy time constant (3000 %s), before the next overload cycle can be executed. This means that, when the frequency inverter must supply only e. g. 90 % of its rated current during the unloading phase, it requires
3000 %s / [100 % - 90 %] = 300 s
until it is can be overloaded again. If the frequency inverter must supply e. g. only 50 % of its rated current, the next overlaod cycle cannot begin before 60 s are over:
3000 %s / [100 % - 50 %] = 60 s.
