Industrial DC motors take on new applications

Edited by the Engineeringtalk editorial team Mar 26, 2002

Leroy Somer has extended its LSK range of industrial DC motors, further increasing the range of applications for which they are suited.

Leroy Somer has extended its LSK range of industrial DC motors, further increasing the range of applications for which they are suited.

The laminated frame motors are now available in ratings from 2 to 750kW and with both compensated and non-compensated types to choose from, there is a model for most industrial DC requirements.

The square-framed, drip-proof motors with in-built forced ventilation provide ingress protection to IP23S as standard across the full power range.

For applications requiring higher levels of protection, a totally enclosed version is available with IP55 protection in power ratings from 1.2 to 36.5kW.

LSK motors are extremely compact, in most cases offering similar output from one frame size smaller than competitive units.

This means, for example, that a torque of 563Nm and power of 123kW at 2080rev/min can be achieved with a 160 frame instead of a 180 - an 11% reduction in size for the same output.

By paying careful attention to cooling of vital components including the brushes and commutator, reliability has not been compromised by the reduced dimensions or higher IP ratings.

The LSK range uses the new International Cooling (IC) classification to describe the cooling system.

Standard LSK motors are rated IC 06, indicating cooling by a fan mounted on the motor and free circulation of air.

Larger motors can be cooled by a range of options, including air-air or air-water heat exchangers designated IC 666 or IC 86W6.

"The most critical area in a dc motor is that around the brush gear and commutator", says Peter Waldock of Leroy Somer UK.

"In designing the new models, Leroy Somer has improved the cooling in this area so that, even with the increased output, the operating temperature of the commutator has not increased".

Other key features of the LSK range include highly accurate assembly to ensure concentricity of the armature in relation to the stator, and the use of standard ball bearings to accommodate the forces due to overhung loads on the shaft.

The concentricity of the armature has a great impact on the magnetic force acting on it and, in turn, the ability to cope with overhung loads resulting from the use of pulleys, belts and chains.

"The production of the LSK uses new machining and balancing methods, together with automat-ed handling, to allow surfaces on the shafts, end-shields, bearings, arma-ture and stator to be finished more accurately", says Waldock.

This improved accuracy also means the LSK range can absorb radial forces which are up to 70% higher when using standard ball bearings, and 375% higher if roller bearings are used.

Working to better tolerances also allows bearing life to be extended to 20,000 hours or more.

A range of options is also available for the LSK series to increase its versatility still further.

These include mechanical as well as electrical braking, a selection of nonstandard flanges, speed feedback devices and brush wear limit detection.