In late-2018 Electrical Machines received an enquiry from a Taiwan-based agent on behalf of a plastic products producer to see if it could design and manufacture a specially customised medium voltage motor for it.
Posing with the specially customised 775kW 16-pole motor shortly before it was dispatched to Taiwan from Electrical Machines’ factory are (from left): Okkie Nel, Senior Design Draughtsman; Derek Wood, Engineering Manager; Johnny Nunes, Design Engineer; Martin Abbot, Draughting Manager; and JA Erasmus, Contracts Engineer.Posing with the specially customised 775kW 16-pole motor shortly before it was dispatched to Taiwan from Electrical Machines’ factory are (from left): Okkie Nel, Senior Design Draughtsman; Derek Wood, Engineering Manager; Johnny Nunes, Design Engineer; Martin Abbot, Draughting Manager; and JA Erasmus, Contracts Engineer.
It was looking for a 775kW 16-pole 3300V 60Hz motor to operate at a slow speed for its application of driving a reciprocating compressor in a hazardous area in the plant. The design had to be a single bearing arrangement design that shared a bearing with the load. In addition, international certification was required. The order for the motor was received in early 2019.
As part of meeting the customer requirements, there were three major motor design components:
l A single bearing motor design sharing a common bearing with the compressor.
l A pressurised motor to meet the hazardous area requirement.
l Ingress protection testing.
The single bearing design required a special shaft seal at the drive-end of the motor. This seal was required for both mechanical considerations as well as the pressurised enclosure requirement. In addition, a unique support was required at the motor drive-end so that the motor could be tested.
International certification was done through TUV Rheinland of Germany. Explolabs, a local authority, was contracted to conduct the local inspections and testing and to correspond with TUV.
As this was the first export pressurised MV motor that Electrical Machines has made for hazardous environments, a number of purging and over pressure tests were conducted. The design incorporates a purge controller with a relief valve. The ingress protection testing had two components to it, namely:
l Testing for dust ingress; a purpose-built dust chamber was manufactured for this test.
l Testing for water ingress; a wet spray test was conducted.
Due to the COVID-19 restrictions on international travel, the certification of the motor had to be conducted remotely with TUV, with videos and digital medium being used by Electrical Machines and Explolabs to show key manufacturing and test procedures and outcomes.
Thanks to the efforts of Derek Wood, Electrical Machines’ Engineering Manager, and Johnny Nunes, Design Engineer, all certification as well as customer requirements were met. The motor was completed in June 2020.
