In case of very long motor and feedback sensor cables please check the following recommendations:
Motor connection
1) Mount some inductance in series with the motor wires (immediately after the drive motor output terminals).
Remarks:
– the additional inductance value should be selected function to the minimum required inductance and to the minimum required electrical time constant (L/R). These values are presented in the “Electrical Specifications” chapter from the drive user manual.
– since the cables are very log, their resistance can’t be neglected. It should be taken into consideration, when the electrical time constant is computed..
2) There should be different cables for motor and feedback sensor(s) connection.
3) The motor cable should be shielded and the shield needs to be connected to one of the drive GND terminals, in one of the sides and to the motor case, in the other side.
Remark: If possible, a double shielded cable is preferred for the motor cable. In this case the inside shield will be connected to one of the drive GND terminals while the external shield will be connected to one of the drive GND terminals, in one side and to the motor chassis, in the other side.
4) The motor cable should have an extra wire (even a double shielded cable is used), that will be connected to the GND terminal, on the drive side and to the motor case, on the motor side.
Feedback sensors connection
1) The encoder must be differential.
2) A shielded cable with twisted wires must be used for the feedback sensor connection.The shield needs to be connected to one of the drive GND terminals.
3) The feedback sensor wires must pass through a different cable than the motor wires.
4) An 150 Ohms resistor is required between the A+ and A- / B+ and B- / Z+ and Z- encoder wires. These resistors will be mounted near the drive.
5) When the feedback sensor(s) supply wires section will be chosen, the voltage drop on these cable must also be take into consideration. The main reason is that the feedback sensors must receive enough voltage to work properly. For example, if the drive outputs 4.8 V, on the “+5V output” and the encoder needs 4.5 V, the voltage drop on the supply wires can’t be bigger than 0.3 V. Otherwise the encoder will not work.
6) A minimum 10 uF capacitor is recommended to be mounted (near to the motor) between the +5V and GND wires, that are used for the feedback sensor(s) supply.
Remarks:
– the drive and the motor setup (specially the current controller tuning) must be performed with the long wires and all additional electronic components connected to the drive.
– if the electrical time constant (L/R) is still to small, after the additional inductance was mounted, the PWM frequency can me increased up to 80 kHz , taking care to keep the same sampling periods for the slow and fast loops (1 ms for the slow loop and 0.1 ms for the fast loop).