87C Whitby Road, Slough, SL1 3DR
Telephone: (01753) 576477 Fax: (01753) 825661
Website: www.ceerelays.co.uk
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87C Whitby Road, Slough, SL1 3DRTelephone: (01753) 576477 Fax: (01753) 825661 Website: www.ceerelays.co.uk
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Modelling Variable Speed Drives in PTWAlthough PTW does not have a specific variable speed drive (VSD) model, VSDs can be easily modelled. The method of modelling VSDs depends on the objective of the study, and on whether the VSD has a bypass switch, and how you want it to be modelled. The VSD can be displayed as a 2-node annotation symbol on the SLD, which is a direct connection between the line side and load side of the VSD. This would only graphically display the existence of a VSD, without having any effect on the study. It is the motor connected to the load side of VSD that needs to be modelled properly, depending on the type, and objective, of the study. The motor model needs to be changed only for a short-circuit study, when the VSD has no bypass (or the bypass is off). In these cases, increase the sub-transient impedance of the motor defined in the ANSI/IEC Contribution Subview of the Component Editor to a high value to represent zero contribution from the motor. For load flow and harmonic analysis the motor model can be modelled as normal, with the correct harmonic model assigned to it, if a harmonic study is being run. Normally, there is no need for modelling VSDs in TMS, because the starting current of the motor does not exceed the nominal current. |
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