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Power MeasurementMeasuring on Electrical Machines
Hardly a motion that is not carried out by an electrical drive, hardly no drive motor with any kind of electrical machine, hardly an electric motor that is not operated by a frequency converter. Efficient technologies are required, best efficiency factors are demanded and highly accurate measurements are therefore necessary. Such drives cause an increased adoption of power electronics and all implications connected with that such as circuit feedback, broadband frequency spectra of current and voltage, pulse-frequency modulated signals and fast slew rates of the voltage impulses.
Task
Modern frequency converters use various algorithms in order to simulate voltage and currents. They all have in common that electric switches (IGBTs) are used that have steep rising edges (3 kV/µs) and high pulse frequencies (up to 40 kHz). Broadband measurements with high dynamics for voltage and currents are, in this case, necessary to fulfill the following tasks:
- Exact identification of active power
- Identification of reactive power, also in case of high phase angles
- Identification of power loss
- Efficiency factor (also mechanical parameters)
Especially for the identification of efficiency factors several power measurements are required at the same time: 3~ grid, 3~ motor, 1~ intermediate circuit, rotation speed and torsional moment are not uncommon. Measuring these parameters synchronously and accurately is the big challenge.
Solution
DEWETRON‘s solutions for this application are DEWE-PM instruments with the DEWE-ORION cards 1616-500 or 0816-1000 and DAQP-HV-S3 modules for measuring voltage and DAQP-LV modules for measuring current.
Beside the standard functions of power measurement instruments, several additional measurements are required to be able to carry out a complete analysis of the motors:
- ± 1400 Vpeak
- 4 kV electric strength
- 700 kHz bandwidth
- 1 MS/s sampling rate
- Typical accuracy of < 0.05 %
- Individual number of channels
- Several power modules in one instrument
- Video recording in parallel
- Synchronous analysis of harmonics and frequency
- DC, 16.7 Hz, 50 Hz, 60 Hz, 400 Hz, 800 Hz, variable frequencies
- Mathematical library (e.g. calculation of various efficiency factors)
- Every power module can have its individual frequency (software PLL)
- System perturbation for frequency converters according to EN61000-3-2
- Power curve and characteristic curve of revolutions per minute (rpm) and torsional moment
- Electrical characteristics such as harmonics, fundamental power, reactive power, switching operation, run-up
- DC-measurements in the frequency converter
- Analysis as regards grid, motor, intermediate circuit and – mechanically – the drive shaft (Welle)
- Voltages up to 1000 VRMS directly measurable (DAQP-HV module)
- Analyses of run-up with data storage and processing
- Mechanical parameters such as rotation speed and vibration of the motor and the shaft respectively
- Acoustic emission (sound power level, frequency spectrum)
Hardware
Only one DEWETRON measurement instrument is needed to carry out all these measurements. Based on the new DEWE-PM-series it is quite easy to define the appropriate hardware solution for you. With up to 16 input channels several power modules can be used in order to e.g. synchronously measure parameters regarding grid, motor and intermediate circuit. Additionally, revolutions per minute, torsional moment, temperature and acoustic level measurement can be carried out. The enormous range of DEWETRON modules and sensors makes synchronous measurement and evaluation of parameters possible. Great importance was attached to the development of these instruments as regards interference resistance. The frequency converter thus benefits from the strong common-mode rejection voltage. Another contribution to the interference resistance is the high electric strength.
Software
The option power for the DEWESoft is a very high-capacity tool for the calculation of power and other similar parameters. Due to the calibration in the frequency range a high accuracy of the calculated values is reached. With the help of this unique technology amplitudes and phase can be corrected in the frequency domain. All internal correction curves were incorporated in the software and the sensor data base includes all correction curves for current and voltage converter or whatever sensor is used. Beside the precise calibration the frequency calculation is a central feature of the software. 50 and 60 Hz are a must – for us also DC and variable frequencies are, of course, a must. Due to the high sampling rate (up to 1MS/s) and the modules there is no limitation to the recording of pulse-width modulated signals (up to 700 kHz electrical bandwidth) and the calculation of active, reactive and total power, power factor, etc.
Some Details
Many Power Modules
With the DEWESoft power module an arbitrary number of power modules can be measured at the same time.
Motors e.g. Ugrid/UDC/Umotor
FFT– Harmonics Analysis
- U, ULine, I, P, cos P and Q
- Individual setup of number of harmonics including DC (example: sampling rate 20 kHz = max. 200 harmonics @ 50 Hz)
- Values adjusted to the actually measured frequency of fundamental oscillation
- Frequency analysis up to 500 kHz
Remote Control
With the help of the remote control the instruments can be configured from afar – for example while being in the office.
Plug-in OPC
The OPC-plug-in for DEWESoft provides the integration of the measurement instrument in the scada system and thus the implementation of automated test benches. OPC is a standardized protocol for the transmission of data from several measurement instruments (OPC server) to one central computer (OPC client).
Acoustics/Acoustic Level Measurement
Accurate and high-resolution acoustic level measurements according to IEC 60651, 60804, 61672. With its user-friendly interface DEWESoft brings the sophisticated acoustic level measurement/acoustic analysis to the user.
Customers
- Producers of motors
- Producers of frequency converters
- Users of drive systems
- Plant engineering
- Testing institutes
- Universities and research centers
Please check out our pre-configured standard models for power measurement. Standard models meet approximately 80 % of all application requirements, are cost optimized and shipped faster.
Technologie AG