An operating manual is mostly written for the operator and may contain no motor data. In that case, the machine's rating plate, the wiring diagram, the spare parts list, the purchase documents and correspondence with the manufacturer quoting the serial number are the most reliable sources.

DRG-90L-6 1.1 kW 1000 rpm aluminium-frame DRG three-phase motor – no motor information in the manual

Where to look in the documents

  1. Wiring diagram: Kept inside the panel door or in a separate file. Each motor is usually labelled “M1, M2” and so on, often with its power written alongside.
  2. Spare parts catalogue: In exploded drawings the motor is shown with a part number; the description line often includes kW and speed.
  3. Machine rating plate: Shows the total installed power, voltage and frequency. On single-motor machines this value points directly to the motor.
  4. Purchase and service records: Old invoices, the maintenance log or the receipt for an earlier rewind may contain the motor values.

Sources beyond the paperwork

When queried with the serial number, the machine manufacturer's technical service can tell you which motor was used in production. The motor plate on the same machine at another company can also help; just make sure that machine is the same model and year. As a last resort, the frame dimensions of the existing motor and the machine's operating speed are assessed together.

When the sources disagree

If the diagram says 1.5 kW while the motor itself shows 2.2 kW, the machine may have been modified earlier with a different motor. In such cases, base your decision on the physical dimensions of the motor currently fitted and on the period when the machine ran without problems, and note the discrepancy between diagram and plate.

You can check frame compatibility by comparing the information you have gathered with the DRG technical drawings, then review the three-phase motor options in the shop.