User manual
3U Servo Amplifier
Motor lead noise is either common-mode or differential. The common-mode conducted currents occur
between each motor lead and ground (line-to-neutral). Differential radiated currents exist from one motor
lead to another (line-to-line). The filtering of the lines feeding the motor provides additional attenuation
of noise currents that may enter surrounding cables and equipment I/O ports in close proximity.
Differential mode currents commonly occur with lengthy motor cables. As the cable length increases, so
does its capacitance and ability to couple noise from line-to-line. While every final system is different
and every application of the product causes a slightly different emission profile, it may become necessary
to use differential mode chokes to provide additional noise attenuation to minimize the radiated
emissions. The use of a ferrite core placed at the Geo Drive end on each motor lead attenuates differential
mode noise and lowers frequency (30 to 60 MHz) broadband emissions to within specifications. Delta
Tau recommends a Fair-Rite P/N 263665702 (or equivalent) ferrite core.
Common mode currents occur from noise spikes created by the PWM switching frequency of the Geo
Drive. The use of a ferrite or iron-powder core toroid places common mode impedance in the line
between the motor and the Geo Drive. The use of a common mode choke on the motor leads may
increase signal integrity of encoder outputs and associated I/O signals.
Backplane Board 19