Mjerenje relativne vibracije rotora primjenom senzora linearnog pomaka bez kontakta
With the Balanset-1A možete mjeriti relativnu vibration of the rotor koristeći kodere linearnog pomaka bez kontakta.
1.1 Odabir vrste senzora i postavljanje
Ovisno o zadatku, za mjerenja se mogu koristiti senzori vibracija ili senzori pomaka. Za odabir vrste senzora potrebno je na ploči “Vrsta senzora” (na dnu glavnog prozora) staviti oznaku u polje “Vibro” ili “Linearni”.
Fig. 1. The main working window of the Balanset program.T
Before starting the measurement it is necessary to make sure that the conversion coefficients of the sensors are set correctly. For this purpose press the button “F4-Settings” in the main working window of the program (see Fig. 1) and go to the settings window designed for entering conversion coefficients (see Fig. 2).
In the working window shown in Fig. 2, in the corresponding fields the conversion coefficients of linear and vibration sensors should be entered. These coefficients are specified in the instrument passport. Usually you do not need to change them.
For the linear displacement senzori korišteni u setu instrumenta Balanset-1A, koeficijenti pretvorbe su redom jednaki:
- Kprl1= 0.94 mV/μm (conversion coefficient of the sensor of the 1st channel);
- Kprl2 = 0.94 mV/μm (conversion coefficient of the sensor of the 2nd channel.
For proper operation, the linear encoder must be installed at a certain distance from the surface of the object of measurement. The nominal clearance between the surface and the end of the sensor is 3.5 mm. In this case there is a constant voltage of 2.48 volts at the sensor output. This voltage will be shown in the fields “Channel1” and “Channel2” for the first and second channels respectively.
To compensate it you must press the button “Remove DC”. A small residual offset will not interfere with the measurement.
Fig. 2. Working window for entering conversion coefficients and selecting the type of used sensors
Pažnja! Navedene vrijednosti nominalnog zazora i faktori pretvorbe linearnih enkodara dati su za rotore od čelika. Za rotore od ostalih metala (bakar, bronza, aluminijum) nominalni zazor i koeficijenti pretvorbe senzora trebaju biti određeni eksperimentalno od strane korisnika provođenjem kalibracije.
To save the changed parameters press “OK” button. The new parameters will be saved in a file and used for further measurements.
1.2 Mjerenje radijalne ekscentričnosti rotora
Radijalna ekscentričnost rotora može se mjeriti beskontaktnim senzora blizine u dvije korekcijske ravnine prema shemi prikazanoj na sl. 3. Kako bi se izmjerila i prikazala vremenska funkcija i spektar ekscentričnosti rotora, ako je potrebno, mora se provesti niz pripremnih operacija, uključujući:
- – select diametrical sections of the rotor, in which the measurements will be carried out;
- instalaciju beskontaktnih linearnih senzora pomaka 5 i 6 i phase senzora kuta 7 na krovat stroja koristeći specijalne uređaje (npr. magnetne tronošce);
- – connect proximity sensors of linear motion to connectors X1 and X2, and phase angle sensor to connector X3 of the measuring unit;
- – set a nominal measuring gap ∆ between the rotor surface and the sensing element for each linear encoder (for the rotor made of steel ∆ = 3.5 mm);
- – place on the rotor the reflective mark required for triggering for the phase angle sensor 7 and check the sensor triggering;
- povezati mjerni uređaj sa računarom.
Fig. 3. Measuring the radial run-out of the rotor
If you press the button “F8 – Charts” in the main working window (see Fig. 1), the computer display shows the working window “Graphs” (see Fig. 5), designed to build different kinds of graphs of radial run-out of the rotor.
Fig. 5. The working window of the “Charts” mode
Dugmići u ovom prozoru grade sljedeće grafike:
- When you press the “Broadband vibration” button in this window, the time function of the rotor radial runout is displayed.
- If the “Rotation frequency vibration” button is pressed, the time function of the reciprocal component of the rotor radial runout is displayed.
- If you press the button “Harmonics (1/rev)”, the display will show a decomposition graph of the rotor runout into a harmonic series. The first harmonic corresponds to the value of vibration at the reverse rotor frequency (1x), the second one – at the double frequency (2x), etc.
- By pressing the button “Spectrum (Hz)” the display shows the spectrum of the radial run-out of the rotor.
- By pressing the button “Orbit” the graph of rotor orbit (precession) is displayed.
1.3 Izgradnja grafa orbite rotora
Construction of the rotor orbit graph can be performed according to the scheme shown in Fig. 6.
Fig. 6. Scheme of rotor orbit measurement 1a – rotor (end view); 1b – rotor (side view); 2, 3 – non-contact sensors; 4 – reflection mark of phase angle sensor.
In order to make a measurement and build a corresponding graph, it is necessary to carry out a number of preparatory operations, including:
- – install the non-contact linear encoders 2 and 3 in one of the diametrical sections of the rotor at an angle of 90° to each other, provided that the measuring axis of encoder 2 must coincide with the X axis, and the measuring axis of encoder 3 must coincide with the Y axis;
- set the nominal measuring gap ∆x (∆y) between the rotor surface and the sensing element of each linear encoder (for steel ∆ = 3.5 mm);
- – set the phase angle sensor (not shown in the scheme) in the X – Z plane, coinciding with the installation plane of non-contact sensor 2;
- – set a reflective mark 4 on the rotor 1 in the X – Z plane, which is necessary for the phase angle sensor operation;
- – connect non-contact linear encoders 2 and 3 to connectors X1 and X2, and phase angle encoder to connector X3 of the measuring unit;
- povezati mjerni uređaj sa računarom.
Kako bi se započelo mjerenje orbite rotora u glavnom radnom prozoru (vidjeti Sl. 1) pritisnite dugme “F8 – Grafike” i idite u radni prozor “Grafike” (vidjeti Sl. 5), koji je namijenjen za izradu različitih vrsta grafika radijalne ekscentričnosti rotora. U ovom radnom prozoru trebate pritisnuti dugme “Orbita”, nakon čega se na displeju računara pojavljuje radni prozor u kojem se provodi potreban ciklus mjerenja (vidjeti Sl. 7).
Fig.7. Graph of the rotor orbit. Balanset software.
To continue the work in the specified working window (see Fig. 7) you must turn on the rotor rotation and by pressing the “F9 – RUN” button perform measurement of the instantaneous values of radial run-out of the rotor Sxi and Syi for a period equal to one rotor revolution.
The array of instantaneous values Sxi and Syi obtained during measurement is used to plot the orbit of the controlled rotor (each i-th point of the orbit has the coordinates Sxi, Syi). The instantaneous radial displacement magnitude is calculated by the formula:
S∑i = √ (Sxi² + Syi²) (1)
where S∑i is the instantaneous value of the radial displacement magnitude (the length of the radius vector of the rotor orbit), calculated for the i-th point of the graph;
- Sxi – instantaneous value of the radial run-out of the rotor, measured along the X axis with sensor 2 (see Fig. 6) in the i-th point;
- Syi – instantaneous value of the rotor radial run-out, measured along the Y axis with sensor 3 (see Fig. 6) in the i-th point.
