Rockwell Automation SA3100 AC Power Modules - Manual (Page 105)

Motor Cables D-3
Optional Cable Terminator
Voltage doubling at motor terminals, known as reflected wave phenomenon, standing
wave, or transmission line effect, can occur when using long motor cables with IGBT
PWM Power Modules.
Inverter duty motors with phase-to-phase insulation ratings of 1600 volts or higher
should be used to minimize effects of reflected wave voltages on motor insulation life.
Applications with non-inverter duty motors or any motor with exceptionally long leads
may require an output inductor or cable terminator. An inductor or terminator will help
limit voltage reflection at the motor to levels which are compatible with the motor
insulation rating.
Table D.1 lists the maximum recommended cable length for unterminated cables
since the voltage doubling phenomenon occurs at different lengths for different Power
Module ratings. If your installation requires longer length motor cable lengths, a
reactor or cable terminator is recommended.
Optional Reactors
The reactors listed in the SA3100 price list can be used for Power Module input and
output. These reactors are specifically constructed to accommodate IGBT inverter
applications with switching frequencies up to 20 KHz. They have a UL approved
dielectric strength of 4000 volts, opposed to a normal rating of 2500 volts. The first two
and last two turns of each coil are triple insulated to guard against insulation
breakdown resulting from high voltage.
Common mode cores will help reduce the common mode noise at the Power Module
output, and guard against tripping of the Power Module caused by capacitive leakage
effects. The RMS capacitive currents are larger at higher PWM carrier frequencies.
When using motor line reactors, it is recommended that the Power Module PWM
frequency be set to its lowest value to minimize losses in the reactors.
Important: Using an output reactor will cause the effective motor voltage to be lower
because of the voltage drop across the reactor. This may also result in a
reduction of the motor torque.