Page 271 - Industrial Power Engineering and Applications Handbook

11/250 Industrial Power Engineering and Applications Handbook
SECTION 2 for windings must undergo tests at the initial inspection
stage before use. Stage inspection is carried out during
processing of the various motor components. Figure I 1.1
11.2 Testing of electrical machines identifies vital parts of a motor and the corresponding
specification standards, on which these components can
be checked and tested. Instruments and gauges used for
This section covers only the tests that are essential on a inspection must be periodically calibrated and checked
completed motor, irrespective of the manufacturing for dimensional accuracy.
procedure and stage quality checks. If IS0 9000 guidelines
are assimilated, practised and enforced by a manufacturer
so that a customer’s trust is obtained, a final pre-despatch Purpose of testing
inspection by the customer may not be necessary. The The purpose of testing an electrical motor is to ensure its
customer, having gained confidence in the practices and compliance with the norms of design, material inputs
Quality Assurance Systems of the manufacturer, may and manufacturing accuracy. It determines the mechanical
issue an authorization to the manufacturer to despatch soundness and electrical fitness of the machine for its
the material under their ‘own inspection certificate’, rather electrical and mechanical performance. Such tests deter-
than an inspection by the customer. We discuss below mine the following:
the test requirements procedure and the acceptance norms
prescribed by various national and international standards
for such machines and adopted by various manufacturers. 1 Mechanical aspects: vibration and noisc level.
To fulfil the above requirements the material inputs 2 Electrical aspects: guaranteed output and performance.
for the motor, such as stampings, steel, enamelled copper 3 Temperature rise at the guaranteed output to ascertain
wire, insulations and varnishes, bearings, enclosure the adequacy of the insulating material and life of the
materials and hardware must be subjected to a series of motor. If the temperature rise is more than permissible
acceptance tests according to norms and standard for the type of insulation used, it will deteriorate the
specifications. For example, enamelled copper wire used insulating properties and cause thermal ageing. As a

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Figure 11.1 IS specifications for various parts as used in an electric motor