Hitachi SJ300 / L300P E07 Overvoltage and Braking Workflow

Step 1 — Classify the operating moment

The first split is whether the drive tripped during acceleration, steady running, deceleration, stop, lowering or at power-up. E07 during deceleration is an energy route; E07 at idle or power-up is more likely line or sensing evidence.

Record this before changing ramp parameters. A changed ramp can hide the evidence needed to decide whether the system is under-braked or the drive is misreading the bus.

Step 2 — Decide whether the machine is regenerating

Fans, centrifuges, hoists, downhill conveyors, unwind sections and high-inertia machines can drive energy back into the DC link during a stop. If coast-to-stop or a longer deceleration time changes the fault, the case is no longer a generic drive failure.

Use that observation to separate load/ramp work from resistor and brake-chopper evidence.

Step 3 — Qualify the installed braking route

Identify whether the rating uses internal braking, optional external braking unit or a separate resistor cabinet. Collect resistor value, power rating, duty-cycle information, thermal switch state and wiring evidence. A missing or open resistor can produce the same operator symptom as a board-level failure.

If the resistor is too small or the stop duty is too frequent, the correct fix may be a braking-system change, not a repaired drive.

Step 4 — Escalate to sensing only when the field path is closed

The DC-bus sensing path is relevant when the external route makes no sense: normal line voltage, no regenerative event, healthy braking route and an E07 that appears at inconsistent timing. At that point, bus feedback and control-board interpretation become repair evidence.