By TEBAOFLEX Jyen. Originally published on December 31, 2025.
A servo cable may combine motor power and protective earth with brake or temperature-sensor circuits. Feedback may use a separate cable or an approved hybrid arrangement. The correct construction depends on the drive, motor, feedback protocol and motion profile. Similar connector size or jacket colour does not establish interchangeability.
Separate the circuits and their requirements
- Motor phases and protective earth: current, voltage waveform, insulation, bonding and cable-length limits.
- Holding brake: supply voltage at the motor, release current, switching arrangement and suppression components.
- Temperature sensors: sensor type, wiring method, permitted resistance and interference requirements.
- Feedback: protocol, pair allocation, impedance, supply voltage, shielding and connector pin assignment.
PWM power circuits can couple interference into nearby circuits. Individual pair screens and an overall shield may be part of the OEM design, but no universal braid percentage or foil-plus-braid construction guarantees trouble-free operation. Use the specified screen termination and separation arrangements. A holding brake and its cable are not automatically a safety-rated stopping system.
Illustrative 5 V encoder supply calculation
Assume, for illustration only, a 5.00 V supply, 0.25 A load, 35 m one-way length and conductor resistance of 138 ohm/km. With equal outgoing and return conductors, drop = 2 × 0.035 × 0.25 × 138 = 2.415 V. The assumed load would receive 2.585 V, before connector losses.
If a different hypothetical conductor has resistance 39 ohm/km, the same calculation gives 0.6825 V drop and only 4.3175 V at the load. That still does not meet an assumed 4.75 V minimum. Larger conductors alone therefore do not prove that this example works.
Some encoder interfaces provide remote-sense connections; Beckhoff’s AX5000 documentation shows optional supply-sense lines. They work only with compatible supply regulation and correct wiring. Do not add sense wires or raise a supply voltage beyond the equipment instructions. Check temperature-dependent resistance, connector drop and maximum allowed voltage at light load.
Encoder and resolver cables are not interchangeable
A resolver uses excitation and analogue return signals; an encoder interface may use digital, analogue or combined signals. Voltage, pair count, impedance and shielding requirements follow the specific interface. Not every encoder uses 5 V, and not every feedback cable has remote sense.
Qualify movement and connector assembly
A drag-chain rating must state bend radius, travel, speed, acceleration, temperature, cycle definition and test criteria. Conductor class describes conductor construction and resistance; it does not certify the finished cable for ten million cycles. Torsional robot motion requires separate consideration from planar chain motion.
For an M23 or other circular connector, match the exact insert, coding, contact ratings, pinout, backshell and cable diameter. Environmental protection depends on the correctly assembled and mated connector system. A factory assembly is not automatically IP67 or error-free merely because it uses an M23 shell.
Replacement and commissioning checklist
- Record both OEM part numbers and revision-specific wiring drawings.
- Confirm all power, brake, sensor and feedback pin assignments before connection.
- Verify shield bonding, protective-earth continuity and strain relief to the equipment instructions.
- Inspect the full motion envelope for pull, twist, tight bends and rubbing.
- Request traceable continuity and electrical test records, plus relevant movement qualification; do not apply generic high-voltage tests to connected electronics.
Use the circuit and movement documentation to compare replacement offers. A purported drop-in equivalent should be supported by a drawing and ratings covering the actual equipment, not by a generic performance table.
Sources and application documentation
Discuss the application
Send the application duty, installation drawing and required acceptance criteria to TEBAOFLEX. WhatsApp: +86 185 9591 3361. Request the applicable product documentation before ordering.