The central exhaust system of a production hall has several fans. The fan power is decisive for the quality of the exhaust process in the entire production hall.
An exhaust air system is required for various production processes. It is used to exhaust soldering vapours and vapours from the laser marker, and to ensure machine availability and thus the smooth operation of the entire production process. Needs-based maintenance is therefore essential.
In order to realise this, the current values of all three phases are detected on one of the fans, in addition to the already integrated vibration monitoring. Measuring the phase difference provides additional information about the condition of the fan motor.
A compressor failure in this plant has far-reaching consequences:
In the worst case, this leads to a total failure of the entire production area.
The vibration monitoring of the fan and its data sent to moneo provide information to detect possible damage.
But additional data on the electrical condition of the fan and the upstream frequency converter are necessary for a comprehensive assessment.
The aim is to ensure the fan's operability by monitoring:
moneo|RTM is centrally installed on a server. The IO-Link masters are connected to the server via an internal VLAN.
ifm has a wide range of automation components. Three ZJF055 current converters and the AL2605 IO-Link input/output module were chosen for this application.
The current converters are used for all supply lines of the three AC phases U/V/W between the frequency converter and the connection terminals on the fan. The measured values of the converters are provided as 4...20 mA analogue signals on the signal outputs. These values are converted from 4...20 mA to IO-Link signals via the AL2605.
The data is made available to moneo|RTM via an IO-Link master of the AL1352 series.
The values of the current consumption of the three supply lines U/V/W are to be measured with the help of three current converters.
To obtain useful process values, the measured value of the current converter must be converted into the actual current value (4 mA ≙ 0 A, 20 mA ≙ 50 A) of the converter. This is done in moneo RTM via the function "Calculated values".
The following electrical and mechanical damage patterns can be detected:
The determined current values are used to
Thanks to comprehensive data recording, imminent faults can be detected at an early stage. Maintenance work can thus be scheduled and carried out as needed. This adds a decisive factor to the process reliability of the entire plant.
Current values allow conclusions to be drawn about possible short circuits on the motor winding, sluggishness of rotating components and faults in the frequency converter.
Get the big picture on the moneo dashboard.
The dashboard provides the user with an overview of the relevant process values for this plant.
The analysis function can be used to access historical data and compare different process values. The diagram shows the current values of U, V and W in mA.
Here it can be clearly seen that in the start-up phase ① there is an overshoot, while in normal operation ② the current value settles. In the switch-off moment ③ there is a small peak due to the inductances in the motor.
The so-called current asymmetry should not exceed 10% for three-phase machines. For each difference value, an alarm is created if the value is ≥10%.
Monitoring with regard to a warning limit value has not been implemented as the tolerance band of up to 10% may be used when the fan motor starts up or sudden load changes occur.
This function can be used to easily define what should happen after a warning or alarm has been triggered, e.g.:
For applications where maintenance measures are necessary, it is advisable to plan the service call in good time.
The “Calculated values” function is used to further process the process data. In this use case, various further processing operations are carried out:
In this use case, all 3 phases of the drive motor are monitored, which means that the calculation sometimes has to be carried out several times.
The current converter used provides an analogue signal of 4..20 mA which first must be converted into a process value in mA. This must be done for all 3 phases.
Motor current = (AIN-4,000) * ((AEP-ASP)/(16,000)) + ASP
To calculate the current asymmetry, the differential current between the individual phases (U-V, V-W and W-U) must first be calculated.
∆Motor current = motor current U - motor current V
In order to be able to indicate the current asymmetry in %, it is first necessary to create a 100 % basis by determining the average value of the 3 phases.
Average current = (motor current U + motor current V + motor current W)/3
The current asymmetry in percent is calculated from the current differences (U-V, V-W and W-U) and the average current of all three phases. This value is required for creating limit values in this use case.
Current asymmetry = (∆motor current)/(avarage current) * 100%