Scope of this technical record
Altivar ATV61 / ATV71 output path from PWM bridge to U/V/W terminals, motor cable, motor insulation, load and current-feedback evidence for OCF and SCF decisions.
Do not connect insulation-test equipment through the drive output. Isolate motor and cable correctly, verify discharge and follow the installed-drive manual before touching output or DC-link terminals.
ATV61 / ATV71 output path route
The output path explains why motor, cable and load evidence must come before board conclusions.
Output-path decision matrix
The output path decides whether OCF/SCF evidence still belongs outside the drive or has moved inward to current feedback and bridge hardware.
| Path area | Decision | Evidence |
|---|---|---|
| Terminals / cable | External fault possible | Loose strands, insulation, moisture, routing |
| Motor / load | Machine-side current demand | Brake release, jam, load profile |
| Bridge / feedback | Drive-side suspicion | Static checks, channel comparison, repair history |
Why the output path is the center of OCF and SCF
OCF and SCF both become confusing when the output path is treated as a black box. The useful path is physical: output bridge, gate-driver command, U/V/W terminals, cable, motor terminal box, motor windings, mechanical load and current feedback. The fault code tells the technician where to begin; the path tells them what must be proven before moving inward.
This path also protects replacement decisions. A new module can fail immediately if the cable, motor or brake cause is still present. A good circuit-path page therefore links field checks to bench checks instead of replacing one with the other.
Output path evidence order
The output path should be worked from the external machine inward unless the evidence already proves an internal bridge short. This is especially important where several people have already reset the drive, changed parameters or replaced a module.
Output path checkpoints
| Path area | Evidence to collect | What it decides |
|---|---|---|
| U/V/W terminals | Loose strands, tracking, contamination, output accessory wiring | External terminal fault versus drive-side suspicion |
| Motor cable | Insulation, moisture, shield/PE handling, cable movement | Cable leakage or phase-to-phase fault |
| Motor terminal box | Water ingress, glands, winding insulation | Motor-side root cause |
| Mechanical load / brake | Free rotation, brake release, jam or overload | OCF caused by demand rather than electronics |
| Output bridge | Static evidence after external proof | IGBT/module or bridge damage |
| Current feedback / driver | Channel plausibility and previous repair history | Drive-side repair boundary |
OCF versus SCF on the same physical path
OCF often needs load and setup evidence because the current may be real and excessive without a hard short. SCF needs a stricter stop condition because the protection is reporting short-circuit or grounding evidence on the output. The same output path is used, but the tolerance for repeated powered testing is different.
If SCF is present, the page should push toward insulation and transistor/static evidence before another start. If OCF is present during acceleration, the page should preserve motor data, ramp and brake evidence before treating the drive electronics as faulty.
Field-to-bench handoff
The handoff to a repair bench is valid only when it states what happened at the field boundary. A board photo alone does not prove why the output stage failed. The output path page asks for both sides: motor/cable/load facts from the machine and driver/current-feedback facts from the drive.
- U/V/W terminal and motor-terminal-box photos
- Cable route, shield/grounding and output-accessory evidence
- Insulation result taken with the drive isolated
- Brake/load state when OCF appears
- Static output and driver evidence if drive-side work begins
Field record checklist
- Output terminal condition
- Cable and motor insulation
- Motor terminal box environment
- Mechanical load and brake state
- Output bridge static evidence
- Driver/current feedback boundary
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Used to anchor OCF around hardware current limitation, motor data, high inertia, excessive load and mechanical blockage.
Used to anchor SCF1 around drive output short/grounding, motor cable checks, motor insulation and transistor test routing.
OEM programming and fault-reference context for Altivar 71 diagnostic pages.
OEM installation and wiring context for safe output and motor-cable evidence collection.
Turn this record into a qualified service request
A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.
- Complete drive type code / MLFB or nameplate model
- Fault code, fault value and first event before reset
- When the event appears: power-up, enable, ramp, run, decel or stop
- Motor/cable connected or isolated during the symptom
- Visible board, option-card, module and connector identifiers
- Previous repair history, replacement parts and repeat-failure pattern