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In modern electric traction drives, on-line monitoring offers the advantage to decrease maintenance cost and increase the reliability. Especially, the electrical insulation is one of the most vulnerable components of an ac machine. Fast switching of the inverter results in high output voltage slew rates increasing the stress on the insulation as well as the rate of deterioration. The described stator...
Condition monitoring of inverter-fed drives is gaining a more important role. Inverter operation enables maximum utilization of a drive. However, some parasitic phenomena may occur, e.g. bearing currents, temperature increase due to additional losses and stress caused by fast voltage rise times. With focus in this work on stator winding insulation an online monitoring method is presented to detect...
At inverter-fed traction drives stray currents due to parasitic capacitances in frequency converters and machine cause high frequency voltage components spreading into all conductive components of the drive system. These hf voltages are harmful and origin from the inverter side through fast switching power semiconductors with high levels of output voltage steepness. Additionally overvoltage at the...
The demand for AC machines in traction applications fed by voltage source inverters is increasing. These highly efficient drives working near and even above their rated values are expected to operate for many years or even decades. Thus, condition monitoring is gaining a more important role. With focus in this work on outages due to deteriorated machine winding insulation an online monitoring method...
Reflected wave transient phenomena in voltages and currents of inverter-fed drives caused by voltage source inverters (VSI) operating with pulse width modulation (PWM) with high dv/dt rates are well known and analyzed in many studies. The reflection phenomena occurring at the machine terminals, resulting in high overvoltages are one reason for the stress and aging mechanism of AC machines insulation...
Insulation condition monitoring is important in case of inverter-fed machines due to the high strains on the machine and especially on its winding insulation system. In particular in traction applications the usage of new emerging semiconductor technologies, which enable higher inverter switching frequencies and rapid voltage rises, transient overvoltages at the machine occur. The insulation system...
Stator insulation defects in the machine winding of traction drives can be analyzed by evaluating the current response resulting to inverter induced voltage injection. Due to effects occurring during the aging of the insulation, e.g. change of parasitic electrical components, deviations of the high frequency components of the current response can be monitored. The insulation degradation of a stator...
In order to investigate insulation degradation of high voltage traction drives, series of measurements on form wound coil specimens have been done. These stator bars have been aged by different accelerated aging cycles until the failure of the insulation is determined by voltage exposure tests. After every aging cycle the dissipation factor (tan δ) and capacitance (C) of the insulation system is recorded...
The proposed online monitoring method detects insulation defects in a machine by evaluating the current response after a certain voltage step excitation is applied. The transient current response is analyzed to determine the status of an electrical machine insulation regarding aging, in a longer perspective. If insulation degradation occurs the parasitic winding components (e.g. winding capacitances)...
Stator insulation defects in traction drives machine windings can be analyzed by evaluating the current response after a voltage step excitation. The status of the stator insulation material regarding aging, is observed in a longer perspective. Because of the fact that insulation degradation of a stator winding system is a long developing process, a deviation of the parasitic electrical components...
In this work a method to detect stator insulation degradation of traction drives based on analyses of the transient current reaction caused by inverter switching is proposed. Two simple excitation methods are proposed to analyze the state of the inter-turn insulation as well as the groundwall insulation. With the standard hall-effect based closed loop current transducers used for the control of the...
In modern drive applications fed by voltage source inverters, monitoring systems are of advantage to reduce the maintenance costs and prevent outages. The proposed insulation monitoring method detects stator insulation defects by evaluating the current's transient response after step excitation by the inverter. Due to fast switching of the voltage source inverter at high output voltage dv/dt rates,...
In this work a method to detect insulation degradation of an adjustable speed drive (ASD) based on analyses of the transient current reaction caused by inverter switching is proposed. The drive system consists of an inverter fed three phase induction machine with 1.4MW. The standard current sensors are used to analyze the transient signal ringing to extract an insulation state indicator of the winding...
The demand of monitoring systems to prevent a breakdown of electrical machines is continuously increasing. Regarding economic issues, usage of system resources and additional components to establish monitoring is restricted. With the method proposed, the evaluation of the stator insulation condition of all three phases is possible using only the two current sensors already available in modern drive...
In modern traction drives the application of monitoring systems is growing to ensure continuous operability. Because of the voltage source inverters (VSI) and the high steep voltage change (dv/dt), increased stress of the winding insulation exist. Stator insulation faults are common reasons for a machine breakdown. Insulation health state can be examined by evaluating the transient reaction to a voltage...
Application of monitoring systems is growing in modern drive applications to ensure continuous operability. Insulation health state can be examined offline by evaluating the transient reaction to a voltage step excitation. Using the inverter as a source of excitation, it is possible to perform an insulation test by evaluating the resulting transient current sensor signals available in modern drives...
In modern traction drive applications condition monitoring is getting more and more important. Insulation health state monitoring can be done by evaluating the high frequency current response to voltage step excitation by the signal analyses of the current sensors, which are also used for the control of the machine. This reduces the costs and number of necessary system components. A change in the...
A high number of breakdowns of adjustable speed drives (ASD) is caused by a fault of the machine, especially stator related insulation faults frequently occur. The evaluation of the insulation condition is possible with the current sensor signals only. The analyses of the transient part of the current response give evidence if a change in the insulation system occurred. The degradation of the insulation...
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