Scope of this technical record
Circuit-path explanation for SJ300 / L300P output-current detection, connecting fault timing, current transformer or feedback route, noise and control-board input before gate-drive conclusions.
This is not a live-measurement procedure. It defines evidence categories for qualified service personnel working under proper isolation and discharge procedures.
Current feedback is not the same as output silicon
A drive can trip overcurrent because output current is genuinely high, because feedback reports current incorrectly, or because noise and harness conditions corrupt the detection path. Those are different repairs. The current-detection path is the bridge between field symptoms and board evidence.
E04 deserves special attention because public documentation links it to other conditions including current-transformer error or noise-induced error. That makes it a candidate for a sensing route after external causes are cleared.
Evidence hierarchy
The hierarchy is operating state, external output proof, current-feedback plausibility, CT/harness/noise evidence, then control-board input boundary. If a technician skips the hierarchy, the case can become a costly parts loop.
Field record checklist
- Fault code and operating state
- Motor/cable evidence
- CT/harness/noise evidence
- Control-board input boundary
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Public SJ300 troubleshooting chapter used to confirm E01-E04 overcurrent timing, E09 undervoltage context and trip-history discipline.
Public L300P manual used to confirm E01-E04 overcurrent definitions, trip threshold context and E04 current-transformer / noise / DC-braking boundary.
Reviewed internally for SJ300 5.5 kW and 7.5 kW current-detection, output-stage and gate-drive evidence. Drawing files are not redistributed as public sources.
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