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Expansion of our turbo-compressor motors

The VEM Group always focuses on meeting customer requirements. This goes hand in hand with the constant development of motors with increasing performance. This was also the case with an order received by the Sachsenwerk in Dresden in June 2019, which has further expanded our already existing product portfolio and will continue to do so.

Technical data and application of the motor

A compressor with the following parameters was ordered:

  • output 40MW
  • voltage 11kV
  • speed 1,500 rpm.

The electric motor is a drive for a turbo compressor for compressing process gases in the petrochemical industry. The compressed gas is then broken down into its components or fed into a chemical process and is further processed.
The motor is designed as a synchronous salient-pole machine with screwed-on solid pole roofs. Start-up is carried out with the aid of a multilevel voltage DC link converter which, with its almost sinusoidal output voltage, creates no additional insulation stress and causes only low losses. After ramping up to nominal speed Unenn and synchronisation, the system switches to mains operation with 11 kV.

Why this electric motor is so special

One of the challenges in the electromagnetic and constructive design was the realisation of a Roebel bar winding with Vacuum Pressure Impregnation (VPI). Since the manufacture of these motors is technologically sophisticated, many more design details are to be taken into account compared to small motors such as a 25 MW motor.
In order to determine the optimum insulation structure, an elaborate grooved model with differently insulated test bars was specially manufactured, VPI impregnated and cured. This made it possible to guarantee the functionality of the selected insulation system for the bar winding with complete impregnation, as well as the extension of power range for low-pole industrial drives up to 80 MW.
In addition, the mechanical requirements for this application should not be underestimated. The mass of the rotor with its copper winding is very large, so that considerable masses must rotate at a relatively high speed and the centrifugal forces are therefore also considerable. In order to be able to control these and realise the capacity of 40 MW, the rotor consists of forged on salient poles. The rotor winding is held in place by pole roofs, which are fastened with screw connections.
Particularly, in the rotor construction, a great deal of development work was invested in the analysis of special coil, pole roof and coil support design.

The gradual expansion of the VEM portfolio

In the past, VEM’s turbocompressor drive portfolio was limited mainly to a capacity of up to 20 MW. However, several projects have shown that the expertise for the production of electric motors with higher capacity is already available at Sachsenwerk. For example, five air-cooled, 4-pole motors with a capacity of 25 MW have been supplied in Ex design, and another has been ordered by the same customer and is currently being manufactured.
VEM has mastered every challenge in this project, which was prove during test runs in the test facility. Finally, the motor was delivered to the customer in July 2020. Two more will follow, one of which is already being manufactured and will be delivered in Q3 2021. The operation and design of the motors are similar.
Currently, a turbo-compressor drive with a capacity of 55 MW is being produced, in which the knowledge from the previous projects is being used in a target-oriented manner. We look forward to further exciting projects and are happy to realise projects with motors of up to 80 MW for our customers.


VEM motors Finland Oy