Electrical motors can be found everywhere and their crucial role is to power various equipment in industrial plants. They are supposed to work continually and any interruption in their work can cause serious problems. For instance in chemical and process industries there are huge revenue losses if motor driven cooling pumps stop working properly.
Statistics show that motors like other rotating machines suffer from serious faults that can be timely predicted with a monitoring system.
Statistics show that motors like other rotating machines suffer from serious faults that can be timely predicted with a monitoring system.
How does EMCM work?
Expert condition monitoring system (EMCM) is a tailor made, online solution for large and medium voltage synchronous motors. The system measures most important motor values and allows plant personnel to get full insight into the motor health.
Thanks to its high level of modularity, almost any motor value can be measured and integrated with monitoring values of gearbox and end application (e.g. pump, fan, turbine, e.c.). The advanced options built into the system help planning maintenance periods and while achieving lower inventory, overhaul and labor costs.
Armed with a complete insight into critical applications, asset managers can predict their lifetime and health.
Thanks to its high level of modularity, almost any motor value can be measured and integrated with monitoring values of gearbox and end application (e.g. pump, fan, turbine, e.c.). The advanced options built into the system help planning maintenance periods and while achieving lower inventory, overhaul and labor costs.
Armed with a complete insight into critical applications, asset managers can predict their lifetime and health.
Fault detection with DMFM method
EMCM solution uses DMFM (Differential Magnetic Field Measurement Method) which produces voltage that is proportional to the fault (no fault voltage is close to 0V, but in case of the fault, output voltage is increased).
The method is giving number of broken bars and their locations. The biggest use of the method is in fault detection of rotor broken bars because the measurement is implemented in air gap (in rotor bars are, closest to the fault).
The method is giving number of broken bars and their locations. The biggest use of the method is in fault detection of rotor broken bars because the measurement is implemented in air gap (in rotor bars are, closest to the fault).
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Using the method in the system - left side shows measurement signal without fault and right side with rotor broken bar
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These two images show the same signal as above, but this time zoomed. It can be seen that the fault signal has more than 3 times higher amplitude than the one without fault, which makes the method ideal for monitoring purposes.
DMFM method gives approx. 200 times higher resolution in fault detection than commonly used CSA method (Current Signature Analysis). The graph below compares these methods.
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Comparison between most commonly used method (MCSA) and new method (DMFM) for broken rotor bars detection |
In order for this method to work, implementation of sensors inside of air gap is needed. These sensors are very thin (0,3 mm) and the rotor needs to be disassembled for sensors to be implemented.
CSA method is based on motor current measurement. Although it does not require machine disassembly, the CSA method has some limitations when working on frequency convertor and also with low motor loads. It also requires human effort for fault recognition.
DMFM pros and cons
+ the best choice for monitoring (reliable, highest resolution, it can give early warnings with cracks of bars)
- machine needs to be disassembled for the installation
CSA pros and cons
+ the best choice for diagnostic purposes
- lower level of resolution
- if used as periodic measuring method, early warnings and predictive monitoring are not possible
CSA method is based on motor current measurement. Although it does not require machine disassembly, the CSA method has some limitations when working on frequency convertor and also with low motor loads. It also requires human effort for fault recognition.
DMFM pros and cons
+ the best choice for monitoring (reliable, highest resolution, it can give early warnings with cracks of bars)
- machine needs to be disassembled for the installation
CSA pros and cons
+ the best choice for diagnostic purposes
- lower level of resolution
- if used as periodic measuring method, early warnings and predictive monitoring are not possible
Smart trending explained
One feature that distinguishes EMCM solution from others on the market is smart trending. What is the difference between smart trending and the standard one that is applied in other systems?
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If a certain value (machine parameter) is observed over a time period, one can easily determine the trend of that parameter. This is true if other process parameters are constant. In the image on the left blue line presents the observed machine parameter (for trending), and the yellow line machine power. It can be seen that the observed machine parameter depends on the machine power.
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If a trend line is applied on the diagram presented in the image above, the end result will be useless, because one can not determine whether value increase is a result of fault or process parameter change. In order to avoid such case we have implemented smart algorithm for data storage. The observed machine parameter is measured along with a process parameter which is divided in 10-20 classes (e.g. 0-5% - class 1, 5-10% - class 2, … 95-100% - class 20).
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If real trending needs to be shown, the measured parameter has to be analyzed only for the time periods which have the same class, as presented with the gray line on the right (gray area represents measured data for the same class).
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If only gray area is analyzed, the rest of the data can be ignored in this case. If one wants to see real trending, this is the proper way. In this case measured data is not influenced by the process parameter.
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This is what real trend looks like. With EMCM you choose one of the classes for a certain process parameter and observe the vibrations in that class. This allows you to follow the trend and to conclude that increased vibrations mean that the motor will be soon experiencing a problem, so site operators can predict the changes and react on time.
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By choosing a restrictive class (most often this is active power) we are trending measured values (vibrations, temperature) only inside of this class. In that way we can get an insight into the machine condition and bring conclusions if some measured value will eventually exceed the alarm limit. If we select the restrictive class of the machine we can see vibration trend for the operating machine only in a selected time period – this allows us to clearly see if vibrations tend to increase, stagnate or decrease in time. As a result, if we see that vibrations are increasing we can estimate with mathematical methods when this vibration will exceed the alarm and value limits. Below is an animation showing the interface and the graphic results for different levels of load from one existing power plant.
The same principles can be applied to vibration, temperature and other machine parameters.
The same principles can be applied to vibration, temperature and other machine parameters.
Which motor types can be equipped with EMCM?
Although EMCM solution can be implemented with any motor type, a general rule is: the more expensive and critical the motor is for the plant process, the greater the need to prevent faults. Our experience so far speaks for some types of motors that increase productivity with EMCM:
- Asynchronous motors
- Three-phase motors
- Synchronous motors
- Motors for hazardous areas
- Gear motors
- High-torque motors
400 kW motors power magnetic drive pumps - an example where motors should not fail.
Application industries and target equipment
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Sugar & Ethanol
Turbogenerators for steam turbines
Induction motors for mill and reparation, defibrators, chippers |
Irrigation
Induction motors for pumps, centrifugal compressors, fans and test laboratories
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Cement
Induction motors for mills and ball mills, rawmills and gas fans
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Pulp & Paper
Turbogenerators for steam turbines
Induction motors for cellulose refiners, centrifugal pumps, wood and paper refiners |
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Mining
Induction motors for ball mills and conveyor belts
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Thermo Power
Turbo generators for gas and steam turbines
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Steel
Induction motors for compressors, metal shredders, centrifugal compressors
Synchronous motors for rolling mills |
Oil & Gas
Synchronous motors for reciprocating and centrifugal compressors
Induction motors for centrifugal pumps |
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Water & Wastewater
Induction and synchronous motors for pumps and waste incineration plants
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Marine
Induction motors for main propulsion, tunnel thrusters, firefighting pump and generator sets
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Engineering field
Induction motors for air separation plants and test benches
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Other applications
Motors for wind power, wind tunnels, hoist motors for harbour cranes
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Benefits for the users.
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EASY IMPLEMENTATION
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CONNECTIVITY
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USER FRIENDLY
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SMART FUNCTIONS
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See for yourself why EMCM is the right solution for you by choosing one of the options below or simply contact us.