Both frames share the same IEC frame codes, IP55 protection and class F insulation; the difference lies in the mechanical behaviour of the material.

CriterionAluminium frameCast-iron (GG20) frame
Power range0.25–11 kW0.55–355 kW
WeightLighter; easier handling and flange mountingHeavier
StiffnessSufficient for light and medium dutiesDamps shock and vibration better
Typical dutyFans, small pumps, packaging, light conveyorsCrushers, screens, mills, heavy conveyors, heavy belt drives

Between 0.55 and 11 kW both options exist; for example a 7.5 kW 1,500 rpm motor is available as 132M in either frame. In this range the decision depends on load type, environment and mounting weight. With high belt tension, constant vibration or shock loads, cast iron is preferred; where the motor must be carried by hand or hung on a light flange, aluminium is an advantage.

Models: aluminium frame motors and cast-iron frame motors; a detailed comparison is in our 11 kW aluminium versus cast-iron article.