The questions you put to the machine manufacturer should reveal not only the motor's power but also how it will operate, how it will be attached to the machine and what loads it will face. Asking for the answers in writing, and with a dimension drawing if possible, prevents mismatches from surfacing later.

DRG-225S-4 37 kW 1500 rpm cast iron frame DRG three-phase motor – questions to ask the machine manufacturer

Questions about load and speed

  1. What power and torque are needed at the machine shaft, and what margin has been added to this value?
  2. At what speed must the machine shaft turn; will speed adjustment be required?
  3. Does the machine start unloaded or under load; is extra torque needed during starting?
  4. How many hours a day does it run, and how many times an hour does it stop and start?

Questions about connection and layout

  1. Will the motor be foot-mounted, flange-mounted or both?
  2. What are the shaft diameter and length, and what size is the keyway?
  3. What are the dimensions of the space set aside for the motor, and which way does the cable enter?
  4. For a belt drive, what are the pulley diameters and belt tension, and how much side load reaches the shaft?
  5. Does the machine require a vertical motor, and if so, shaft up or shaft down?

Questions about operating conditions

Which way should it rotate? Will the machine run on a frequency inverter? Are limits foreseen for ambient temperature, dust or humidity? Does the manufacturer recommend a particular type of motor protection? The parts of these answers concerning protection and connection should be assessed together with qualified electrical personnel.

When you get no answer

If the manufacturer will not share certain data, estimates can be made from values measured on a similar machine or with calculation tools; but such estimates should not be treated as “exact values”. Clearly note any items that remain uncertain before placing the order.

With the information you have gathered, you can run a first screening in the selection wizard, then browse three-phase motors in the shop by power and speed.