maintenancecenter, writer
115
edits
Difference between revisions of "NVGate SOA and CBT techniques"
Jump to navigation
Jump to search
m
NVGate SOA and CBT techniques (view source)
Revision as of 21:30, 12 June 2020
, 21:30, 12 June 2020English edits
m (English edits) |
|||
| Line 1: | Line 1: | ||
This article | This article compares Synchronous Order Analysis (SOA) method to the Constant Band Tracking (CBT) method. | ||
==Applications== | ==Applications== | ||
===Synchronous Order Analysis (SOA)=== | ===Synchronous Order Analysis (SOA)=== | ||
* Balancing / Phase default detection: | * Balancing / Phase default detection: Order 1 is being followed. Phase gives the unbalance<nowiki>'</nowiki>s position. | ||
* | * Coast Down using Bode Plot. Critical frequencies can be detected (Amplitude and Phase) | ||
[[Image:SOA_Vs_CBT_01.png|framed|none]] | [[Image:SOA_Vs_CBT_01.png|framed|none]] | ||
| Line 12: | Line 12: | ||
===Constant Band Tracking (CBT)=== | ===Constant Band Tracking (CBT)=== | ||
* Gear Boxes: shocks are numerous, spectra are noisy. Orders are not identified as clearly as they are in the case of large rotating machines such as turbines for instance. What is | * Gear Boxes: shocks are numerous, spectra are noisy. Orders are not identified as clearly as they are in the case of large rotating machines such as turbines for instance. What is interesting is their is more energy around one order rather than its amplitude. Computation is performed on a constant width frequency band. | ||
===Order Extraction from waterfall=== | ===Order Extraction from waterfall=== | ||
| Line 27: | Line 27: | ||
===CBT=== | ===CBT=== | ||
Constant Band Tracking consists | Constant Band Tracking consists of order analysis calculation based on energy summation from FFT data. Since the FFT module is used when tracking orders with the CBT feature, the trigger block duration is constant and no re-sampling is performed there. As a result, the number of rotations contained in one block depends on the rotating speed.<br> | ||
[[NVGate_CBT_principle_and_settings|See CBT page for more info.]] | [[NVGate_CBT_principle_and_settings|See CBT page for more info.]] | ||
| Line 36: | Line 36: | ||
* FFT trigger block for CBT has a constant time base defined by the frequency resolution. | * FFT trigger block for CBT has a constant time base defined by the frequency resolution. | ||
The example below shows, at two different rotating speeds of a swept sine | The example below shows, respectively the FFT trigger block and the SOA trigger blocks at two different rotating speeds of a swept sine. | ||
[[Image:SOA_Vs_CBT_02.png|framed|none]] | [[Image:SOA_Vs_CBT_02.png|framed|none]] | ||
| Line 48: | Line 48: | ||
This is different in the FFT module where the average time is the same for the whole range of speeds. | This is different in the FFT module where the average time is the same for the whole range of speeds. | ||
* The SOA averaging is done on the exact same number of revolutions at any time of the measurement whereas the CBT will average different number of revolutions at | * The SOA averaging is done on the exact same number of revolutions at any time of the measurement whereas the CBT will average different number of revolutions at a separate time of the test depending on the current rotating speed. | ||
==Swept sine setup emphasizing differences between SOA and CBT techniques== | ==Swept sine setup emphasizing differences between SOA and CBT techniques== | ||
| Line 93: | Line 93: | ||
The setup of the tachometer is very important for the accuracy of the phase results. Since different | The setup of the tachometer is very important for the accuracy of the phase results. Since different setups can lead to slightly different results, it is necessary to know what to pay attention to. The difference between AC and DC coupling will be here emphasized as one of those important settings. | ||
<u>Measurement setup</u>: one tachometer is connected to both Ext | <u>Measurement setup</u>: one tachometer is connected to both Ext Syncs 1 and 2 and both Inputs 1 and 2. The different signals are: | ||
* Train pulses with AC coupling (in black) | * Train pulses with AC coupling (in black) | ||