With the pressure to design high power motor drive electronics with low power losses, switching motor drive amplifiers now have PWM edges that switch 400 Volts as fast as once every 100 ns. While this helps to keep switching losses down, it has made receiving logic level signals from encoders and sensors very difficult. This is because every PWM edge must charge and discharge the motor wiring capacitance. The current spikes to do this can be as large as 4 Amps. This current flow causes the motor frame to have ground bounce on it due to the inductance of the ground return back to the amplifier. This ground bounce and the coupling between motor and encoder harness wires can introduce noise into the system. This section describes wiring techniques that will reduce the interference between motors and encoders.
NOTE: For systems that operate with a 48 V or lower motor bus, the ferrite beads and the 600 V wire that are described in the following sections are not needed.
It is very important that the wiring guidelines in this section be followed in order to avoid encoder quadrature errors, zero index errors, data transmission errors in high frequency serial absolute encoders, communication failures and other noise related problems.