SEW-Eurodrive Fault F07 — Causes & Fix

SEW-Eurodrive Fault F07 — What It Means

SEW-Eurodrive fault F07 means overvoltage on the DC link — the DC bus voltage exceeded the maximum allowable threshold. On SEW MOVITRAC B, MOVIDRIVE B, and MOVIMOT series drives, F07 is triggered when the DC bus rises above approximately 800–850 VDC on a 480V-class drive, or 400–420 VDC on a 240V-class drive. DC bus overvoltage is typically caused by regenerative energy — kinetic energy from a decelerating load feeding voltage back into the bus faster than the bus can absorb it or dissipate it through a braking resistor.

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Common Causes

• Deceleration ramp too short — If the drive is commanded to stop or slow down quickly, the motor acts as a generator and pumps energy back into the DC bus faster than the internal brake chopper can handle it.
• No braking resistor or undersized braking resistor — High-inertia loads (large fans, centrifuges, hoists) require an external braking resistor to dissipate regenerative energy. Without one, the bus voltage climbs until F07 trips.
• Input overvoltage — If the AC input supply is already at the high end of tolerance (e.g., 500V on a 480V system), the DC bus sits higher than normal and a small regeneration event is enough to trip F07.
• Failed brake chopper — The brake chopper transistor (internal to the drive) is supposed to activate the braking resistor when bus voltage rises. If the chopper has failed open, no energy is dissipated and F07 follows.

Step-by-Step Fix {#fix}

1. Increase deceleration ramp time — In SEW MOVITOOLS or via the keypad, find the deceleration ramp parameter (Ramp t11 in MOVITRAC B, Ramp 1 in MOVIDRIVE). Increase it significantly and test. This is the most common fix.
2. Check braking resistor — If the application requires fast stops or has high-inertia loads, verify a braking resistor is installed and correctly wired to the brake chopper terminals (BW+ and BW on SEW drives). Measure resistor continuity.
3. Measure input voltage — Check the AC input at the drive terminals. If supply voltage is high (>510V on a 480V system), F07 will appear at deceleration rates that would be fine at nominal voltage.
4. Test the brake chopper — With the drive in a controlled test, monitor DC bus voltage during deceleration. If bus voltage climbs above the chopper activation threshold without the resistor heating, the chopper may have failed.
5. Reset the system — After increasing deceleration time or installing/verifying the braking resistor, reset the fault via the keypad (STOP/RESET key) and test a complete stop cycle.

Parts Often Needed

When to Call a Pro

If the braking resistor is correctly sized, installed, and tested good, but F07 persists, the internal brake chopper transistor may have failed. SEW-certified technicians can test the chopper circuit and replace the relevant IGBT module.