How to solve Error Code 7

Fault code:

【7】Bus overvoltage hardware protection

Reason:

Pump voltage rise caused by energy feedback: When the load driven by the inverter is in a generating state (such as motor deceleration, elevator descent, frequency converter braking), kinetic energy is converted into electrical energy and fed back to the bus. If the energy cannot be released in time, it will cause a sharp increase in bus voltage.

Grid fluctuation: Sudden voltage rise in the grid (such as lightning strikes, transformer switching) or three-phase input phase loss, resulting in the rectified DC bus voltage exceeding the rated value.

Sampling circuit error: voltage sampling resistor deterioration, poor contact of voltage divider circuit, resulting in sampling values higher than actual voltage, triggering protection incorrectly; Or the sampling value lags behind and the protection is not triggered in a timely manner.

Solution:

Insufficient release of braking energy: Increase the power of the braking resistor or connect multiple sets of resistors in parallel to improve the release capacity. Optimize the brake drive circuit to ensure fast conduction.

Grid surge suppression: Install varistors or filters on the input side to absorb transient over-voltages; The three-phase system can be equipped with three-phase AC contactors to cut off the input in case of overvoltage.

Phase loss protection: By detecting phase loss through hardware logic circuits, triggering relays to cut off power and avoid DC voltage imbalance after rectification.

Sampling circuit calibration: Replace the deteriorated sampling resistor (if the error exceeds 5%, it needs to be replaced, and metal film resistors are preferred); Add RC filtering circuit to eliminate sampling noise and avoid false triggering.

Note: Please do not dismantle the machine without permission, otherwise it will be out of the warranty of Ktech.