Order analysis

An order analysis is the analysis of the noise or vibrations of rotating machines. In contrast to the frequency analysis , the energy content of the noise is not plotted against the frequency , but against the order.

The order is a multiple of the speed.

example

A motor rotates at 3000 revolutions per minute, which corresponds to a mains frequency of 50 Hertz for a two-pole AC / three-phase motor . The first order is then at 50 Hz, the second order at 100 Hz, the third at 150 Hz, etc.

The order analysis is carried out either at a fixed, constant speed or for an entire run-up in which the machine is accelerated from the lowest to the highest speed. Such an analysis is also called signature analysis .

Procedure

From the Fourier analysis : A Fourier transformation is carried out at certain speeds . The spectrum is converted into an order spectrum based on the current speed.

In the angular range

In the past, the measurement signal was not scanned equidistantly, but scanned in angle-synchronous fashion using special hardware. If such an angle-synchronous signal is transformed into the frequency range, an order spectrum is created. Today the normally scanned signal is converted into an angle signal with the help of the speed pulses recorded at the same time. A Fourier transformation is then carried out. The result is an order spectrum.

Tracking filter

Often the entire spectrum of orders is not of interest, only the level of a single order. This can be calculated with the help of a tracking filter. The center frequency of a bandpass filter is varied with the speed.