Question:
What needs to be considered for L-force devices of the 9400 series with regard to the leakage currents when using earth-leakage-circuit-breakers?
Answer:
Regarding the leakage currents, the 9300 and 9400 can almost be handled in the same way.
1.) The motor cables (Lenze system cables up to 2.5 mm²) of L-force 9400 devices of size 1 and 2 are of low capacitance. When using a 300 mA earth-leakage-circuit-breaker, there are no problems to be expected with these motor cables.
2.) In the case of L-force 9400 devices of size 3 and higher (13 A…24 A), the leakage current can be 180 mA when using a 100m-shielded cable (Lenze system cables of 4 mm² and higher are not of low capacitance). It has to be considered that a 300 mA earth-leakage-circuit-breaker can be activated as of 150 mA (50 % of the rated tripping current). The maximum leakage current should not exceed 1/3 of the rated tripping current of the earth-leakage-circuit-breaker.
The following measures can be taken to reduce the leakage current:
- Use low-capacitance motor cables
- Choose motor cable lengths as short as possible
- If required, increase the switching frequency to 8 or 16 kHz
- Use IT power supply units (9300) / remove the IT mains bridge (9400) in conjunction with a summation low-leakage RFI filter on the mains side
