Method for maintenance of a frequency converter and software program realizing the same

Method for maintenance of a frequency converter configured to drive an electric motor of a transportation device, said frequency converter being supplied with AC mains power via a contactor, and including a rectifier circuit for providing a DC supply voltage, a capacitive intermediate circuit for leveling DC supply voltage, and an inverter circuit for providing power to the electric motor, wherein said method comprises:

• after the transportation device has been vacant for a predetermined time period, opening said contactor to disable power flow from mains supply to the frequency converter;
• connecting a test load to the intermediate circuit, parallel to a capacity of the intermediate circuit;
• detecting the DC supply voltage Udc(t);
• and
• utilizing the detected DC supply voltage Udc(t) for establishing a maintenance information indicating that a maintenance should be done on the frequency converter, the maintenance information being established before a failure arises, wherein the test load is one of a braking chopper circuit, a machinery brake, and a motor winding, wherein the maintenance information is indicative of a certain kind and/or severity of problem of the frequency converter, wherein the established maintenance information is transferred or made accessible to a remote maintenance center or a mobile service unit or a local control unit of the transportation device, depending on the 25 kind and/or severity of problem indicated by the maintenance information.