Noise-reduced special design of 3000 rpm squirrel cage motors

Menzel specializes in manufacturing new electric motors as well as re-machining and modifying existing motors for the most unique and challenging industrial applications. Through various measures, we were able to reduce the noise emissions of these TEFC ribbed cooled low-voltage motors according to customer specifications.

Motor performance data

• 3-phase squirrel cage motor
• Nominal power: 315 kW
• Nominal voltage: 400/690 V
• Standard: IEC / EN 60034-1
• Nominal speed: 3000 1 / min
• Installation: IM B3
• Protection: IP55
• Cooling: IC411 TEFC ribbed cooled
• With grey cast iron housing
• Weight: 1760 kg

Highly utilized but low-noise electric motors - is that possible?

Respecting the ever more stringent environmental and health protection requirements, the construction of low-noise electric motors and the development of noise-reducing measures are becoming more and more important. An optimum of electrical and mechanical quality should be found, taking economic aspects into account, however at the same time the motor should be as quiet as possible. These are demands that in some ways contradict each other.

Globalization and associated cost pressures require the production of highly optimized yet highly utilized machines. However, machines that are used to full capacity with added economical restraints, may have greater problems in terms of noise than machines that are conservatively designed, not used to full capacity. Therefore, noise reduction measures should, if possible, be installed in such a way that there is no output loss, e.g. by changing the cooling air routing or by reducing the air volume.

What causes electric motor noise?

Electric motors consist of a rotating electromagnet that alternatively attracts and repels a permanent magnet. When a motor runs, the noise emission is composed of three components:

• Aerodynamic noise
• Magnetic noise
• Noise from a mechanical element (e.g. bearing noise in motors with roller bearings)

How can the noise from electric motors be reduced?

The bearing noise can be reduced noticeably by using particularly low-noise bearings. 
The magnetic noise can be controlled by a precise pre-calculation of the magnetic circuit and the resulting selection of suitable number of slots ratios for the stator and rotor.

In almost all high-speed, surface-cooled and internally-cooled standard motors, however, the aerodynamic noises are responsible for the majority of the noise emissions. Aerodynamic noises can be reduced through various special designs: reducing the outside diameter of the fan, using direction of rotation dependent fans, and installing a sound insulation hood on the fan side.

• Reducing the cooling fan’s outside diameter 
• Mounting of fans that depend on the direction of rotation
• Installing an extended, sound insulation hood on the fan side

All of these soundproofing measures can also be retrofitted.

Manufacturer for special motor solutions and adjustments

In contrast to large manufacturers, we are able to offer special motor solutions and customer-specific adaptations of electric motors. In our Berlin motor factory, we have all the requirements to meet the needs of our customers, be it a noise-reduced special version, an 1:1 identical replica of an older motor design, a second shaft, special terminal boxes, etc. Just give us a call, our engineers will find the best product solution for your challenge. Implemented quickly and easily in our own factory.

Our manufacturing emphasis is on the production of individual, custom-tailored units, regardless of whether for special applications or as a back-up or replacement. At our modern and extensively equipped motor factory in Berlin, Germany we are able to directly, quickly, and flexibly produce all kinds of special models.