ABB ACS255 User Manual

Also see for ACS255: User manual User guide

ABB ACS255 User Manual Manual pdf 48 page image

4812.5.4. Example of applying Derating FactorsA 5Hp, 400V/460V IP66 drive is to be used at an altitude of 2000 meters above sea level, with 12kHz switching frequency and 45°C ambienttemperature.From the table above, we can see that the rated current of the drive is 9.5 Amps at 40°C,Firstly, apply the switching frequency derating, 12kHz, 25% derating9.5 Amps x 75% = 7.1 AmpsNow, apply the derating for higher ambient temperature, 2.5% per °C above 40°C = 5 x 2.5% = 12.5%7.1 Amps x 87.5% = 6.2 AmpsNow apply the derating for altitude above 1000 meters, 1% per 100m above 1000m = 10 x 1% = 10%7.9 Amps x 90% = 5.5 Amps continuous current available.If the required motor current exceeds this level, it will be necessary to either- Reduce the switching frequency selected- Use a higher power rated drive and repeat the calculation to ensure sufficient output current is available.12.6. Mains Line input ReactorsAn optional Line reactor is recommended to be installed on drives where any of the following site conditions occur:-o The incoming supply impedance is low or the fault level / short circuit current is high.o If the transformer kVA rating is more than 10x the kVA rating of the drive or ensure that the per drive sourceImpedance is less than 0.5%.o The supply is prone to dips or brown outs.o An imbalance exists on the supply (3 phase drives).o The power supply to the drive is via a busbar and brush gear system (typically overhead Cranes).o Reduction in Harmonics generated by the drive.In all other installations, it is good practice to install a line reactor as added protection of the drive against power supply faults.12.6.1. Selecting a Line ReactorThe chosen Line reactor should be in the region of 3% impedance; higher values can be used but will result in less voltage (and less torque) tothe motor as full load is reached.The continuous current rating should be at least the value of the drives input current rating, with a peak current rating of at least 2 times thecontinuous current rating.