KUKA KRC2 KSD Servo-Drive Fault — Is It the Module or the Motor/Cable?
KUKA KRC2 KSD servo fault? A swap-test tells module from motor/cable in minutes. How to identify the KSD by axis and confirm the faulty unit before buying parts.
KSD servo fault — module, or motor/cable?
The message names the domain; a swap-test and a motor measurement confirm it before you order a part.
KSD in the drive rack (redrawn)
Points at the KSD module
DRIVERS ERROR / TRIP,Drives error 71/79/80/105/106→ “Check / Exchange the KSD”.OVERCURRENT Ax→ reduce load or exchange KSD.Parameter error PR1,HEAT SINK TEMPERATURE→ KSD / cooling.SYNCHRONISATION ERROR→ drive-bus Interbus cable (DSE–KPS–KSD).
Points at the motor / cable
MOTOR CABLE Ax(short / ground fault) → “Check motor cable / motor”.FAILURE OF MOTOR PHASE Ax→ “Check motor cable / motor”.- Measure phase-phase resistance + insulation to ground at the arm connector.
- Never measure the motor while the KSD is energized.
Diagnostic path
Sources: KUKA KRC2 ed05 Operating Instructions — §2.7.4 KSD (p.36–37), §10.19 exchange & 600 V (p.101), §11.9 KSD messages (p.116–117).
KSD servo-drive fault — is it the module, or the motor/cable?
The message already tells you which domain to suspect; a swap-test and a motor measurement confirm it before you buy a part.
The question
Three sub-questions in one: is the KSD module itself bad or is it the motor/cable, which KSD corresponds to which axis, and can KSDs be swapped to confirm the fault?
Short answer
Ax). You don’t have to guess module-vs-motor — the manual already splits it by message: text that says “Check the KSD / Exchange the KSD” (drives-error TRIPs, overcurrent, parameter error) points at the module; text that says “Check motor cable / Check motor” (motor-cable, motor-phase failure) points at the motor side; a synchronisation error points at the drive-bus cable. Then confirm with a swap-test (move the suspect KSD to a same-rating axis) plus a motor-cable measurement. Don’t just replace the KSD before the message and the swap agree.
What the KSD is (verified)
Each KSD incorporates the power output stage, current controller, the Interbus interface for the drive bus, motor-current monitoring with short-circuit protection, and heat-sink / communication monitoring (Operating Instructions, §2.7.4, p.36–37). Two frame sizes exist — Size 1 (BG 1): KSD-08/16/32 and Size 2 (BG 2): KSD-48/64; the number “08…64” is the max. current in amps (p.37). Connections per module: X1 control, X13 Interbus IN, X14 Interbus OUT, X2/X3 motor (p.37). Status is shown by one red + one green LED per module (p.36/38).
Read the message — it names the domain
From the KSD message-window table (Operating Instructions, p.116–117), the remedy line is the tell:
Message (per axis Ax) |
Manual remedy → domain |
|---|---|
DRIVERS ERROR / TRIP; Drives error 71 / 79 / 80 / 105 / 106 (µC crash, EEPROM/checksum) |
“Check the KSD → Restart → Exchange the KSD” — KSD module |
OVERCURRENT Ax (overload / I²t) |
“Reduce load on axis (OVR, $ACC_AXIS)… Exchange KSD” — load or KSD |
Parameter error PR1 / HEAT SINK TEMPERATURE Ax |
Check KSD / cooling & load — KSD / thermal |
MOTOR CABLE Ax (overcurrent: short / ground fault) |
“Check motor cable → Check motor” — motor side |
FAILURE OF MOTOR PHASE Ax |
“Check motor cable → Check motor” — motor side |
SYNCHRONISATION ERROR DRIVE MODULE Ax |
“Check Interbus cable between DSE, KPS and KSD” — drive bus |
Source: KUKA KRC2 ed05 Operating Instructions, §11.9 KSD error messages & message-window table, p.116–117. Frame sizes/ratings: §2.7.4, p.37.
Where it sits: the KSD in the drive rack
KPS600 feeds the KSD stack; each KSD drives one axis (X2 motor) and passes the drive bus through (X13 in / X14 out)
Redrawn from the KSD description and connections (Operating Instructions, §2.7.4 / Fig. 2-24, 2-25, p.36–37). Original diagram, not a manual reproduction.
Step 1 — swap-test to separate module from axis
The KSDs are modular and identical within a rating, so the classic confirmation is a swap:
- Note the faulting axis and its KSD position, and the module rating (
KSD-08…64printed on the module). - Swap the suspect KSD with a same-rating KSD from another axis. If the fault follows the module → the KSD is bad. If it stays on the axis → the fault is the motor, motor cable or the feedback (RDC) side, not the drive.
- Match the rating: you may substitute a larger KSD (e.g. KSD-48 for a KSD-32) but never a smaller one; the definitive compatible-module list lives in the motor’s
.SERVOfile, not on the label.
Step 2 — if the fault stays on the axis, test the motor side
Switch off and secure the controller, then wait 5 minutes: up to 600 V can remain in the KPS600, the KSDs and the intermediate-circuit cables after switch-off (Operating Instructions, §10.19, p.101). Never measure a motor while its KSD is energized or connected. Qualified personnel only.
- At the robot-arm motor connector, unmated at both ends, measure phase-to-phase resistance (U–V, V–W, W–U — the three should be balanced) and insulation to ground on each phase.
- Look for a short between phases or a phase-to-ground fault (matches
MOTOR CABLE Ax/MOTOR PHASE Ax); corroded or water-ingressed connectors are a common cause. - Wiggle test the motor cable and both connectors while measuring — catches an intermittent break that a static reading misses.
Could it be the encoder / RDC instead?
If the swap keeps the fault on the axis but the motor and cable measure good, suspect the feedback path, not the drive: a resolver/encoder fault shows as a different family of messages (e.g. code 102/105, “error in data transmission between DSE and RDC”) on the RDC side. That is the subject of the resolver-chain answer — a distinct remedy from a KSD or a motor-cable fault.
Open points / to verify
- The A1–A3 / A4–A6 rating grouping is field practice — confirm the actual
KSD-xxratings on the machine before any swap. - Expected motor phase-resistance / insulation values are datasheet figures, not in the corpus.
- The motor-to-KSD compatibility defined in the
.SERVOfile is referenced by the messages (241/243 servo-file fit) but the file itself is not in the loaded corpus. - Exact message numbers/text vary by KSS 5.x build — key on the message text and the axis number.
Sources: KUKA KRC2 ed05 Operating Instructions — §2.7.4 KSD (p.36–37), §2.8 cooling (p.38), §10.19 KSD exchange & 600 V caution (p.101), §11.9 KSD messages / message-window table (p.116–117).
Request a quote
Looking for a specific configuration, or want to discuss our current stock? Tell us about your project — we reply within 24 hours from our Bilbao office.