MCSA Spectra VI

Owning Palette: Motor VIs

Requires: Electrical Power Toolkit

Calculates the zoom fast Fourier Transform (FFT) spectra of the motor. You must manually select the polymorphic instance you want to use.

Note  Compared with the Spectrum VI and the Harmonic Spectrum VI that use FFT to calculate spectra, this VI uses the zoom FFT to achieve a finer frequency resolution over a narrow span of the baseband frequency range with less memory and processing time.

Details  Example

N Motors

	reset? specifies whether to reset the calculation process. The default is FALSE. When you run this VI for the first time, the calculation process resets automatically.
	waveforms specifies the motor waveforms that the VI uses to calculate the spectra. If you measure one phase of a motor with this VI, specify the one-phase data in waveforms and specify 1-phase signal for algorithm. If you measure three-phase data of a motor, specify the three-phase data in waveforms and specify 3-phase signals for algorithm. t0 specifies the start time of the waveform. dt specifies the time interval, in seconds, between data points in the waveform. Y specifies the data values of the waveform.
	spectrum settings specifies the settings to calculate the spectrum. If you change spectrum settings while the VI runs, the new settings take effect only when reset? is TRUE. number of lines specifies the number of spectral lines to calculate between 0 hertz and maximum frequency. The default is 15,000. % overlap specifies the percentage of data reused by consecutive FFT computations. The value range is from 0 to 100. The default is 0. You can use % overlap to make the computations more responsive when the values of maximum frequency and number of lines require a longer time to produce a new valid output. The VI typically does not return a spectrum each time LabVIEW calls this VI. You can use % overlap to increase the rate at which a new spectrum is computed by reusing acquired data. For example, setting % overlap to 50 causes this VI to compute a new spectrum twice as often as a setting of 0, because each computation reuses half the data. maximum frequency specifies the maximum frequency, in hertz, of the band of waveforms to analyze. The default is 250 hertz. The value range is from 0 to the Nyquist frequency. maximum frequency must be a constant value and not a variable value. Refer to the MCSA Spectra VI Details for more information about calculating the maximum frequency.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	demodulation settings specifies the settings to calculate the spectra. If you change demodulation settings while the VI runs, the new settings take effect only when reset? is TRUE. enable? specifies whether spectra of waveforms is demodulated. The default is FALSE. algorithm specifies the input signal type. This VI uses different demodulation algorithms for different signal types. The default is 3-phase signals. 0 1-phase signal—Specifies to use a one-phase signal from a motor for demodulation. 1 3-phase signals (default)—Specifies to use three-phase signals from a motor for demodulation. The array size of waveforms must be a multiple of three.
	new spectra available? returns TRUE when this VI finishes updating spectra.
	spectrum information returns the spectrum of waveforms. spectra returns the spectra for multiple motors. One array element represents one spectrum for one motor. f0 returns the start frequency, in hertz, of the spectrum. df returns the frequency resolution, in hertz, of the spectrum. magnitude returns the magnitude, in decibels, of the spectrum. The decibel reference is 1 Ampere or 1 Volt if the spectrum of sideband magnitude is demodulated. The decibel reference is the fundamental component magnitude value if the spectrum of sideband magnitude is not demodulated. demodulated? returns whether spectra are demodulated. The output returns TRUE if you specify enable? to be TRUE.
	error out contains error information. This output provides standard error out functionality.

1 Motor with Initial Conditions

	reset? specifies whether to reset the calculation process. The default is FALSE. When you run this VI for the first time, the calculation process resets automatically.
	waveforms specifies the motor waveforms that the VI uses to calculate the spectrum. If you measure one phase of a motor with this VI, specify the one-phase data in waveforms and specify 1-phase signal for algorithm. If you measure three-phase data of a motor, specify the three-phase data in waveforms and specify 3-phase signals for algorithm. t0 specifies the start time of the waveform. dt specifies the time interval, in seconds, between data points in the waveform. Y specifies the data values of the waveform.
	spectrum settings specifies the settings to calculate the spectrum. If you change spectrum settings while the VI runs, the new settings take effect only when reset? is TRUE. number of lines specifies the number of spectral lines to calculate between 0 hertz and maximum frequency. The default is 15,000. % overlap specifies the percentage of data reused by consecutive FFT computations. The value range is from 0 to 100. The default is 0. You can use % overlap to make the computations more responsive when the values of maximum frequency and number of lines require a longer time to produce a new valid output. The VI typically does not return a spectrum each time LabVIEW calls this VI. You can use % overlap to increase the rate at which a new spectrum is computed by reusing acquired data. For example, setting % overlap to 50 causes this VI to compute a new spectrum twice as often as a setting of 0, because each computation reuses half the data. maximum frequency specifies the maximum frequency, in hertz, of the band of waveforms to analyze. The default is 250 hertz. The value range is from 0 to the Nyquist frequency. maximum frequency must be a constant value and not a variable value. Refer to the MCSA Spectra VI Details for more information about calculating the maximum frequency.
	initial conditions specifies initial internal VI conditions to guarantee consecutive calculation correctness. If you use this VI for the first time or reset? is TRUE, this VI automatically creates the initial internal conditions. Otherwise, wire the most recent final conditions to the subsequent initial conditions to inherit the conditions.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	demodulation settings specifies the settings to calculate the spectrum. If you change demodulation settings when the VI runs, the new settings take effect only when reset? is TRUE. enable? specifies whether spectrum of waveforms is demodulated. The default is FALSE. algorithm specifies the signal source type to use different demodulation algorithms. 0 1-phase signal—Specifies that the signal type is a one-phase signal from a motor for demodulation. The array size of waveforms must be one. 1 3-phase signals—(default) Specifies that the signal type is three-phase signals from a motor for demodulation. The array size of waveforms must be three.
	new spectrum available? returns TRUE when this VI finishes updating the spectrum.
	spectrum information returns the spectrum of waveforms after calculation. spectrum returns the spectrum of the motor. f0 returns the start frequency, in hertz, of the spectrum. df returns the frequency resolution, in hertz, of the spectrum. magnitude returns the magnitude, in decibels, of the spectrum. The decibel reference is 1 Ampere or 1 Volt if the spectrum of sideband magnitude is demodulated. The decibel reference is the fundamental component magnitude value if the spectrum of sideband magnitude is not demodulated. demodulated? returns whether spectrum is demodulated. The output returns TRUE if you specify enable? to be TRUE.
	final conditions returns the final internal VI conditions after the internal calculation of this VI. Use final conditions as initial conditions of the subsequent iteration except that you want to customize the conditions according to your needs.
	error out contains error information. This output provides standard error out functionality.

MCSA Spectra Details

Because the band of waveforms that the VI analyzes is between 0 hertz and maximum frequency, set the maximum frequency value large enough to cover all frequencies for analysis according to your needs. For example, when you detect broken rotor bars, ensure that you specify the maximum frequency input of this VI using the following formula for the spectrum that is not demodulated:

Maximum Frequency > Fundamental Frequency + 2 · Harmonic Order · Slip · Fundamental Frequency

where Maximum Frequency is maximum frequency to specify in this VI,

Fundamental Frequency is the value of the frequency output or the frequencies output of the Frequency VI,

Slip is the value of the slip output of the Speed Estimation VI,

Harmonic Order is the highest order of the rotor bar sideband.

Ensure that you specify the maximum frequency input of this VI using the following formula for the demodulated spectrum:

Maximum Frequency > 2 · Harmonic Order · Slip · Fundamental Frequency

where Maximum Frequency is maximum frequency to specify in this VI,

Fundamental Frequency is the value of the frequency output or the frequencies output of the Frequency VI,

Slip data is the value of the slip output of the Speed Estimation VI,

Harmonic Order is the highest order of the rotor bar sideband.

Related Information
Delta Connections
Power Transmission

Example

Refer to the Motor Monitoring.lvproj in the labview\examples\Electrical Power\Motor Monitoring directory for an example of using the MCSA Spectra VI.