Insulating Systems for High Voltage Motors

Rudolf Brütsch, Von Roll Switzerland Ltd.

High voltage motors cover nominal voltages of 3.3 – 15 kV with power outputs between 0.1 and 50 MW. They are widely used in industry sectors where high power is required; typical examples are mining, pulp and paper, oil and gas, chemical, automotive, cement and other industries. The range of applications covers pumps, refiners, mills, compressors, blowers, fans, conveyor systems etc. High voltage motors have to run in harsh industrial environments; efficiency, reliabilty and low-maintenance operation are therefore key elements. Design and manufacture of the machines have to deal with these criteria. The insulating system of a high voltage motor has a substantial influence on all these factors. It is therefore important that it is carefully selected and applied.

 

Materials mostly used for the main wall insulation of high voltage coils are glass-backed mica tapes with an epoxy, polyester or polyesterimide binder resin. Other backing materials used for smaller motors are polyester film or fleece. Application technologies are the resin-rich process and global vacuum pressure impregnation. These insulating materials and application technologies have been developed and optimised over a long period and can be regarded as mature systems. Nevertheless innovations are being made in this field. They enable motor manufacturers to improve the performance of their machines and reduce costs. Examples of such innovations are:

 

§        Samicafilm insulated wires

§        New mica tapes and VPI resins with improved properties

§        Slot corona protection tapes with increased thermal resistivity

§        Fast curing consolidation materials

§        Flat coil technolgy

 

The paper will describe these innovations in detail and give examples for their application.