What causes Okuma OSP alarm 1157?

Faulty motor insulation (winding short to ground or between phases). Damaged motor power cable or connector shorted by coolant/chips. Failed inverter unit output stage. Mechanical seizure causing extreme load current.

How do I fix Okuma OSP alarm 1157?

1. Read the code number shown with the alarm: code XXXX = U-phase current at time of alarm, signed hexadecimal (tolerance 3FFF); code YYYY = V-phase current at time of alarm, signed hexadecimal (tolerance 3FFF) 2. Note the code: XXXX and YYYY are the U-phase and V-phase currents at the moment of the trip — very high values confirm a real overcurrent, not a sensing error. 3. Lock out power and let the DC bus discharge, then disconnect the motor power cable at the motor and megger-test the motor windings to ground and phase-to-phase for insulation breakdown. 4. Inspect the motor power cable along its run for coolant soak, chip damage, or chafed insulation, and check the connector pins for contamination or carbon tracking. 5. If motor and cable test good, the inverter unit output stage is suspect — do not repeatedly reset and retry, as a shorted inverter can be damaged further. 6. If the alarm returns after these checks, record the alarm number, code and object and contact Okuma service.

Okuma OSP codes

axismd.ai

Okuma OSP Controller

Drive · Intermediate

Alarm 1157

Okuma OSP Alarm A 1157 - MCS Motor overcurrent

The inverter unit detected excessive current in the motor cable of the named axis or spindle. This typically means a short or insulation breakdown in the motor or cable, or a failed inverter output stage.

Okuma OSPDriveIntermediate

1157

Okuma OSP Alarm A 1157 - MCS Motor overcurrent

MCS Motor overcurrent

Common Causes

Faulty motor insulation (winding short to ground or between phases)
Damaged motor power cable or connector shorted by coolant/chips
Failed inverter unit output stage
Mechanical seizure causing extreme load current

Troubleshooting Steps

1Read the code number shown with the alarm: code XXXX = U-phase current at time of alarm, signed hexadecimal (tolerance 3FFF); code YYYY = V-phase current at time of alarm, signed hexadecimal (tolerance 3FFF)
2Note the code: XXXX and YYYY are the U-phase and V-phase currents at the moment of the trip — very high values confirm a real overcurrent, not a sensing error.
3Lock out power and let the DC bus discharge, then disconnect the motor power cable at the motor and megger-test the motor windings to ground and phase-to-phase for insulation breakdown.
4Inspect the motor power cable along its run for coolant soak, chip damage, or chafed insulation, and check the connector pins for contamination or carbon tracking.
5If motor and cable test good, the inverter unit output stage is suspect — do not repeatedly reset and retry, as a shorted inverter can be damaged further.
6If the alarm returns after these checks, record the alarm number, code and object and contact Okuma service.

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