Page 78 - Electric Drives and Electromechanical Systems

Chapter 2 Analysing a drive system 71

FIG. 2.17 A diagrammatic representation of the ALARP principle. Within the ALARP region the costs of removing
a risk have to be justified against the benefits.

Within the ALARP process, a value has to be put on the hazards, its consequence and
control. As can be appreciated this can be a very problematic area, particularly when
human life has to be assigned a monetary value. In addition, the level of risk needs to be
quantified, and while this in engineering terms can be rigorously achieved, the public’s
perceived level of risk is far more difficult to quantify. This can be illustrated by comparing
the public perception of risk between public and private transport.

2.8 Summary

In this chapter the criteria and parameters that affect the selection and sizing of a motor-
drive system were considered. In this process, particular emphasis has to be placed on
the following:

The load torque and the speed reflected to the motor through the power-
transmission chain must be correctly determined. A range of power transmission
elements were considered, and the selection for an application will depend on the
speed and the precision which are required.
The drive and the motor must be suited to the application. Points that should be
considered include the physical environment, the electrical compatibility, and
energy efficancy. In certain cases, the optimum system will need to be modified in
because of the customer’s commercial requirements.
Drives by their very nature can pose a significant hazard to the user or its immedi-
ate environment, hence in all cases a suitable risk analysis should be undertaken.

References

BS 7430:2011þA1:2015, 2015. Code of Practice for Protective Earthing of Electrical Installations. British
Standards Institution.
BS EN 55035:2017, 2017. Electromagnetic Compatibility of Multimedia Equipment. Immunity
Requirements. British Standards Institution.