IEC 60034-18-42-2020 pdf free download

IEC 60034-18-42-2020 pdf free download.Rotating electrical machines — Part 18-42: Partial discharge resistant electrical insulation systems (Type II) used in rotating electrical machines fed from voltage converters — Qualification tests
Machines électriques tournantes — Partie 18-42: Systèmes d’isolation électrique résistants aux décharges partielles (Type II) utilises dans des machines electriques tournantes alimentees par convertisseurs de tension — Essais de qualification.
For insulation systems designed to be used with a power frequency supply, the long-term effects of rated line-to-ground voltage across the mainwall insulation and along the length of the stress control coating are of principal concern. The turn insulation is generally specified by the maximum short rise time surge requirement of the design. Such surge events are generally of very short duration and are relatively infrequent compared to the impulse voltage repetition rate. For this reason, the acceptance requirements are generally satisfied by the ability of the mainwall insulation to endure a power frequency withstand test and the turn insulation to withstand a surge test. The ability of the system to meet the design life requirements is usually satisfied by longer-term voltage endurance testing with sinusoidal voltage. This endurance test allows the designer to establish the long-term capability of the mainwall insulation system.
In the case of converter-fed systems, the more complex voltage waveform produced by the converter drive will provide a different stress distribution in the winding. The mainwall insulation is affected by the magnitude of the voltage overshoot at the fundamental frequency. The stress control system is affected by the magnitude of the voltage overshoot (Ub) at the fundamental frequency and by the impulse voltage repetition rate (/). The latter factor may increase dielectric heating in the stress control system. Both parts of the voltage [5] therefore require consideration in the stress control qualification (see 13.4). The turn to turn insulation may be significantly stressed by the jump voltage (Ui) at the impulse repetition rate (I) but not by the fundamental voltage. As the rise time of the impulses decreases, the voltage stress usually increases on the insulation between adjacent turns on the line end coil of multi-turn coils, thereby producing significant overstress. Very short impulse rise times can affect the life of the turn to turn insulation and the mainwall insulation [6]. The latter is particularly affected if the converter has a small number of levels (e.g. two). However, as a first approximation, the rise time contribution to life reduction of the mainwall insulation can be neglected for long term ageing. The combination of these factors and their effect on the insulation system as a whole are difficult to quantify. Table 2 highlights the most important factors which contribute to accelerated ageing and therefore the assumptions which determine the following test procedures for insulation systems qualification.IEC 60034-18-42-2020 pdf free download.