B3 foot-mounted electric motors are motors fixed to a foundation, chassis or machine body by being bolted through the feet (mounting pads) under the body. B3 is the most common mounting type in the IEC 60034-7 standard and is the motor connection form most frequently encountered in industry.

What Is the B3 Mounting Type?

In B3 mounting, the motor sits horizontally on its feet and the shaft end protrudes horizontally. The motor's feet are fixed to the ground or machine via the holes in the feet. This structure allows power to be transmitted to the load via a coupling, pulley-belt or direct connection.

Advantages of B3 Motors

B3 foot-mounted motors offer easy installation, solid fixing and wide access. The motor can be easily reached during maintenance and service. They are also the most common type, making them practical in terms of spare parts and replacement.

Where Is B3 Used?

B3 foot-mounted motors are used in the great majority of applications that can be fixed to a floor or chassis, such as pumps, fans, compressors, conveyors and general drive systems. Where a flange connection is required, the B5 or B35 type is preferred.

Choosing the Right Mounting Type

The mounting type determines how the motor connects to the machine, and the wrong choice leads to mounting incompatibility. DRG Motor offers motors in the 0.55–355 kW range with B3 (foot), B5 (flange) and B35 (foot-and-flange) options. You can review the mounting dimensions on our technical drawings page.

B3 Motor Dimensions and the IEC Standard

The foot-hole spacing, shaft diameter and frame centre height of B3 motors are determined according to the IEC 60072 standard. Thanks to this standard, motors of the same frame size from different suppliers are interchangeable. Verifying the foot-hole layout and shaft dimensions from the technical drawing before replacement or new installation ensures a smooth setup.

Frequently Asked Questions

What is the difference between B3 and B5?

In B3 foot mounting the motor is fixed to the floor by its feet; in B5 flange mounting the motor is connected to the machine via the large flange at the front. B35 offers both together.

Can I use a B3 motor vertically?

B3 motors are designed for horizontal mounting. For vertical applications, special mounting types such as V1 should be preferred; consult our technical team for the right choice.