Planning the electrical installation39Note 8: Calculating the rise time and the peak line-to-line voltageThe peak line-to-line voltage at the motor terminals generated by the drive as well as the voltage risetime depend on the cable length. The requirements for the motor insulation system given in the tableare ìworst caseî requirements covering installations with 30 metre and longer cables. The rise time canbe calculated as follows: t = 0.8 ∑ ¤LL/(du/dt). Read ¤LL and du/dt from the diagrams below. M ultiplythe values of the graph by the supply voltage (UN). In case of drives with an IGBT supply unit or resistorbraking, the ¤LL and du/dt values are approximately 20% higher.Note 9: Sine filters protect the motor insulation system. Therefore, du/dt filter can be replaced with asine filter. The peak phase-to-phase voltage with the sine filter is approximately 1.5 ◊ UN.Note 10: Common mode filter is available as a plus code option (+E208) or as a separate kit (one boxincluding three rings for one cable).Permanent magnet synchronous motorOnly one permanent magnet motor can be connected to the inverter output.It is recommended to install a safety switch between the permanent magnetsynchronous motor and the drive output. The switch is needed to isolate the motorduring any maintenance work on the drive.¤LL/UNWithout du/dt FilterCable length (m)du/dtUN-------------(1/μs)1.02.05.04.03.01.52.53.54.5100 200 300100 200 3000.00.51.01.52.02.53.0Cable length (m)With du/dt Filterdu/dtUN-------------(1/μs)¤LL/UN5.5
