Types of construction of electric motors

When chosing the right electric motor for the application, the mounting form needs to be considered. The mounting form or also construction type of electric motors are standardized according to DIN IEC 34, Part 7.

Types of construction of electric motors

Table 1: Types of construction according to DIN IEC 34, Part 7

There are 3 main types of construction commonly used for electric motors:
1. Foot mounted types (B3)
2. Foot and flange mounted types (B35 and B34)
3. Without foot, flange mounted types (B5 and B14)

The description of the mounting form of an electric motors consists of the two letters “IM” (International Mounting) plus the specific code, e.g. B3, B5, V1 etc.

In addition to the commonly used basic IM B3 type of construction, motors can also be supplied in other types of construction. Smaller motors up to frame size 160 preferably have type of construction IM B14 with a large or small flange instead of type of construction IM B5.

With IM B5, the fixing screws or bolts are inserted from the motor through the holes in the flange. The IM B14 flange has threaded holes to attach the motor to the driven machine.

Vertical types of construction are also often fitted with a canopy, especially when installed outdoors. This feature is specified for all explosion-protected motors from Siemens where the shaft faces
downwards. For shafts facing upwards, solid parts must be prevented from falling into the fan cover.