FAQ
You only need to installed a suitable current sensor (CT) on distribution panel board of substation relay room, the Motor Patrol which developed by applying motor current signal analysis technology can keep monitor and diagnosis multiple rotating induction motors at the same time also not influence and limit by the environment. You can easily achieve the target of online monitoring and diagnosis the electronic equipment with noninvasive instrument and uncomplicated wiring by the Motor current signal analysis system, MCSA.
When one AC induction motor happens an electrical abnormality, any one of the three phases will be affected by electromagnetic force and the sine wave signal would also be modulated.
Therefore, only one of the phases needs to be measured during online detection. In addition, in order to monitor a clear signal, the motor loading must be at least 75% better, and the motor must be kept under the same load as much as possible before the signal measurement and records to facilitate accurate analysis and diagnosis.
As the above, the operation status of the motor monitored by MCSA should be avoided as far as possible while the load is continuously changed greatly or the frequency of the inverter suddenly changes.
The full function and method of MCSA right now, like Motor Patrol, merely provides detail analysis for the most commonly used AC induction (non-synchronous) motors or generators in the general industry and factory due to the motor operating principles and constructions of various model types are different.
When one AC induction motor has an electrical abnormality or unequal status, any one of the three phases will be affected by electromagnetic force and the sine wave signal would also be modulated. Therefore, only one of the phases needs to be measured during online detection.
There’re two points:
(1) It could be determined accurately to rotor bar damage (or high resistance connection) and stator winding issue because the MCSA method is almost NOT w.r.t. the actual number of motor rotor and stator.
(2) However, only this signature frequency and amplitude of static eccentricity/ dynamic eccentricity of the rotor (uneven air-gap) will be relative to rotor bar’s number in usual, and Ultima Tek already R&D the monitoring solution ( one function of Motor Patrol ) without the demand of bar number.
The diagnostic RPM value is catching from the current flow observation and operating frequency (or central frequency) signature of spectrum analysis, thus the value reliability would be reduce if we are unable to get the motor RPM value. However, we should consider if the RPM frequency signature has no distinguish variation means the motor status is quite normally.
Certainly, the situation with lower loading or even no load will occur these variation of signature frequency too close to the base harmonic wave and then reduce the diagnostic accuracy.
Due to the diagnostic RPM value is catching from the current flow observation and operating frequency signature, thus the value reliability would be reduce(SNR is lower) if the motor rotational speed keeps changing in a short time interval. In the other hand, if the record is able to catching from the constant speed period, the accuracy and daily trend would be improved significantly.
In general, the induction motor is driven by the constant AC voltage, the MCSA online monitoring systems will catching the diagnostic data from this period. If the motor driving mode needs to be variable voltage with time(like feedback control), this would NOT be suit for FFT spectrum analysis of MCSA method.
The motor driven current is related to the torsion(or torque), thus the torsion load variation or fluctuation will reflected on the motor current changing directly. And the driven torsion output problem is able to find out through MCSA monitoring.