Method and apparatus for monitoring a transmission part

A method for monitoring and testing, during operation, the serviceability of a transmission part (4) arranged for transmission of torque between an electric motor (2) and a load (6), said method comprising the steps of:

• A) monitoring (308), during normal operation, the torque of the electric motor,
• B) initiating at least one test sequence if the monitored torque fall below a predetermined value (312), said test sequence comprising the steps of:
• setting a rotation speed of the electric motor at a test rotation speed (604, 614) that differs from the rotation speed of the electric motor (2) immediately prior to said setting, and
• at least registering the time that passes from the setting of the rotation speed of the electric motor (2) until the rotation speed of the electric motor (2) equals the test rotation speed (610, 618), and
• C) sending a signal indicating an error (624) if no further test sequences are to be performed and if said at least one test sequence indicates that said registered time is less than a predetermined value.

A control device (8) for electric motors (2) comprising means (82, 92) for sensing the torque of an electric motor (2) during operation, said control device (8) being characterised in that it comprises:

• A) means (82, 92) for controlling whether the torque of the electric motor (2) fall below a predetermined value,.
• B) means (82, 88, 92) for performing at least one test sequence, said means (82, 88, 92) being arranged to perform said at least one test sequence if said means (82, 92) for controlling indicates that the torque of the electric motor (2) fall below said predetermined value, wherein said means (82, 88, 92) for performing at least one test sequence comprises:
• means (88) for setting a rotation speed of the electric motor (2) at a test rotation speed, which differs from the rotation speed of the electric motor (2) immediately prior to said setting, and
• means (82, 92) for logging the torque of the electric motor (2) within a time period starting from the setting of the rotation speed of the electric motor (2) to the test rotation speed and ending when the rotation speed of the electric motor (2) has reached the test rotation speed, and
• C) means (90, 92) for sending a signal indicating an error if no further test sequences are to be performed and if said at least one test sequence indicates that the logged torque is below a predetermined value.

A control device (8) for electric motors (2) comprising means (82, 92) for sensing the torque of an electric motor (2) during operation, said control device (8) being characterised in that it comprises:

• A) means (82, 92) for controlling whether the torque of the electric motor (2) fall below a predetermined value,
• B) means (82, 88, 92) for performing at least one test sequence, said means being arranged to perform said at least one test sequence if said means for controlling (82, 92) indicates that the torque of the electric motor (2) fall below said predetermined value, wherein said means (82, 88, 92) for performing at least one test sequence comprises:
• means (88) for setting a rotation speed of the electric motor (2) at a test rotation speed, which differs from the rotation speed of the electric motor (2) immediately prior to said setting, and
• means (84, 86, 92) for registering the time that passes from the setting of the rotation speed of the electric motor (2) until the rotation speed of the electric motor (2) equals the test rotation speed, and
• C) means (90, 92) for sending a signal indicating an error if no further test sequences are to be performed and if said at least one test sequence indicates that said registered time is less than a predetermined value.