Reflective Wave Phenomenon; Recommended Motor Cable Length; Emi Filter Installation - Automation Direct DURApulse GS4 User Manual

Appendix A: Accessories
EMI Filter Installation (continued)
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The inverter section of a PWM drive like the GS4 does not produce sinusoidal output voltage wave
forms. Rather, the output voltage produced is a continuous train of width modulated pulses, sent
to the motor terminals via the motor cable.
Peak pulse voltage at the GS4 drive is equal to the drive DC bus voltage and contains steep rise
and fall times, the result of the IGBT switching device used in the drive inverter section.
Peak pulse voltage at the motor terminals may exceed the drive DC bus voltage and is dependent
on the dynamics of the drive output voltage rise time, cable transmission line characteristics,
cable length and motor impedance.
The voltage pulse train at the motor terminals experiences momentary transient over voltage as
the IGBT transistors switch. The result being voltage levels at the motor terminals double that of
the drive bus voltage.
Over voltage of this type has the potential to stress the motor insulation, damaging the motor.
r
eCommended
1) Never connect phase lead capacitors or surge absorbers to the output terminals of the drive�
• As cable length increases, capacitance between cables will increase and may result in leakage
current and over current faults with the possibility of damage to the GS4 drive�
• If more than one motor is connected to the drive, the total cable length is the sum of the cable
lengths from the GS4 drive to each motor�
• Should an overload relay malfunction occur, lower the GS4 drive carrier frequency (P2�10) or install
an output reactor�
2) When operating an AC motor with a PWM drive like the GS4, the motor may experience
reflective wave as described above� To prevent this situation, please observe the
recommendations below:
• Use a motor with enhanced insulation� (1000V, 1200V, 1600V, higher is better)
• Connect an output reactor (optional) to the output terminals of the drive�
• Keep motor cable length as short as possible� (65ft, 20m, or less)
• Where motor cable lengths will exceed 65ft (20m), refer to the Recommended Cable Length
tables below
Page A–6
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Saddle on one end
Figure 2
GS4 AC Drive User Manual – 1st Ed, Rev A - 10/20/2017