F30021 — Power unit: Ground fault

F30021 is the power unit's ground-fault fault: the power has detected a ground fault. The manuals for all SINAMICS families listed here describe the code almost identically. The drive reports the detected ground fault as a fault value in r0949, and the meaning of that value differs slightly between families — see below. One cause and two extra checks apply only to devices connected in parallel.

• Ground fault in the power cables.
• Ground fault at the motor.
• CT (current transformer) defective.
• When the brake closes, this causes the hardware DC current monitoring to respond.
• Short-circuit at the braking resistor.
• Only for devices connected in parallel (r0108.15 = 1) — the manuals describe this for S120/S150 and G130/G150: the closed-loop circulating current control is either too slow or has been set too fast.

1. Check the power cable connections.
2. Check the motor.
3. Check the CT (current transformer).
4. Check the cables and contacts of the brake connection — a wire is possibly broken.
5. Check the braking resistor.
6. For parallel switching devices (r0108.15 = 1) additionally: check the ground fault monitoring thresholds (p0287) and the setting of the closed-loop circulating current control (p7036, p7037).

For the G115D and G120C the manual prints a shorter list of checks: the motor, the current transformer, and the cables and contacts of the brake connection.

• The drive stores the message value as the fault value in r0949; interpret it as a decimal number.
• 0: the hardware DC current monitoring has responded, or there is a short-circuit at the braking resistor.
• Greater than 0: a measured current. On S120/S150 and G130/G150 it is the absolute value of the total current amplitude, where 20479 = r0209 * 1.4142. On G120 and G120XA it is the absolute summation current, where 32767 = 271 % rated current.

• r0949 (fault value) — read the fault value of F30021 here as a decimal number to tell a monitoring response (0) from a measured current (greater than 0).
• r0209 (power unit maximum current / PU I_max) — reference for the total current amplitude in the fault value on S120/S150 and G130/G150: 20479 = r0209 * 1.4142.
• r0108 (drive objects function module / DO fct_mod) — bit 15 shows whether the devices are connected in parallel (r0108.15 = 1); only then do the p0287, p7036 and p7037 checks apply.
• p0287 (ground fault monitoring shutdown threshold / Gnd flt threshold) — check this threshold when devices are operated in parallel.
• p7036 (circulating current control proportional gain / Circ_I Kp) — check its setting in the closed-loop circulating current control on parallel devices.
• p7037 (circulating current control integral time / I_cct Tn) — check its setting in the closed-loop circulating current control on parallel devices.

Remove the cause of the ground fault first. The fault must be acknowledged before the drive will start again; the manuals that state the acknowledgement allow it to be acknowledged immediately, without a waiting period. Once acknowledged, the drive can be restarted.