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DC-link feedback / control-board repair boundary

Hitachi SJ300 / L300P DC-Bus Overvoltage Sensing Path

Defines the repair boundary after line, load and braking evidence are closed: DC-link measurement, bus feedback divider or sensing route, control board interpretation and conditions where a used board or replacement drive becomes the better decision.

Circuit evidence path9 min read

Scope of this technical record

DC-link sensing and control-board boundary for SJ300 / L300P E07 cases after line, load and brake-path evidence are complete.

Safety boundary

DC-link sensing work belongs to qualified service personnel. Use the page to define evidence categories, not as a live test instruction.

Hitachi overvoltage sensing path

1DC bus
→
2Feedback route
→
3Control input
→
4Threshold
→
5Repair boundary

Sensing becomes relevant only after line, load and braking evidence are closed.

When bus sensing is the right question

If E07 occurs at a plausible decel point, treat it as energy management first. If E07 appears at idle, at power-up, or with evidence that does not match line voltage or braking events, the bus sensing path becomes a credible repair boundary.

The sensing route connects the capacitor bank, voltage feedback divider or board sensing input, and the control decision that reports E07. Repair evidence must be tied to the exact frame and board revision.

Field record checklist

  • Line/load/brake route closed
  • Bus behaviour
  • Sensing-route evidence
  • Board labels
  • Donor-board compatibility

Technical basis and reference documents

This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.

SJ300 Troubleshooting and Maintenance, Chapter 6AutomationDirect / Hitachi manual mirror

Defines the status-at-trip context and links E07 to DC-bus overvoltage evidence.

L300P Series Inverter Quick Reference GuideHitachi Industrial Equipment Systems

Lists E06 braking resistor overload and E07 overvoltage protection caused by regenerative motor energy.

SJ300 Dynamic Braking Selection ChartHitachi AC Drive

Shows that braking capability, resistor value, duty cycle and external braking units vary by rating.

SJ300 & L300P Series Inverters Service ManualHitachi America / public service-manual mirror

Describes overvoltage detection by regenerated motor energy or high incoming AC voltage and highlights BRD-duty context.

Evidence intake

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
Prepare request →