Applying the Internet of Things (IOT) to Induction Motor Monitoring
Induction motors are found in all sorts of industries and applications, both on land and offshore.
Smaller Induction Motors (roughly drawing up to 10 Amps Full Load Current) most commonly use Direct Online Starting (D.O.L) methods.
Larger motors typically use starting methods such as Star-Delta starting, which keeps the starting current (surge / inrush) down.
The Internet of Things offers 24/7 monitoring of systems, which can intelligently react based on the input data provided by the networked sensors.
The main parameters of induction motors that could be measured are:-
Voltage (individual phase)
Current being drawn by motor.
Over current in individual phases, such as imbalances due to single phasing faults.
Phase Winding temperature based on measurement using thermistors.
Vibration Monitoring, indicating bearing failure.
Motor speed (inc comparison of actual to Synchronous field speed calculated speed).
What do we mean by the above parameters:-
Firstly lets consider the term, ‘Voltage (Individual Phase)’.
Voltage (individual phase)
The term ‘individual phase’ is applicable in three-phase supply systems.
Three-phase supplies are commonly used in industrial factories and workshops.
It is rare to have a three-phase supply in a domestic home.
To understand a three-phase supply, lets first consider a single-phase voltage supply.
In single-phase voltage systems (as found in most homes), an ac sine waveform ‘cycles’ above and below the centre zero volts level, at a frequency of 50 times a second.
This is known as 50 Hertz, or Hz, and is the supply frequency used in most, but not all, countries around the world.
The picture above, shows a representation of an AC (Alternating Current) Sine Wave. The line through the middle would be zero volts, and as you can see the voltage rises and falls over time (time periods, starting at the left of the picture, and moving right).
For an AC voltage supply frequency of 50 Hz, 50 complete sine waves would be completed, per second.
Now that (hopefully) you understand what a sine wave is, you need to know that in a single-phase system, you have one sine wave, that goes up and down over time (as in above picture).
A three-phase voltage supply, has three sine waves at the same time. NOT ONE, BUT THREE!
Each of the three sine waves, is spaced 120 degrees apart, which means in plain English, that they rise and fall, at different times to each other.
For the purposes of Induction Motor Monitoring, you might want to monitor the phase wire, to check whether the voltage is on or off.
If the Induction Motor was a single-phase type, then obviously if the voltage supply was off, the motor would stop.
However, the single-phase motor may be tucked away from view, in a corner of the factory. Therefore being able to monitor the single individual phase supply, is still useful for an IOT induction motor monitoring system.
Being able to monitor all three voltage supply wires, to a three-phase induction motor, is even more useful.
If one of the three voltage supply wires, to the induction motor stopped supplying voltage, the motor would continue to run.
The motor would not run well on only two supply wires, but may go unnoticed, if in an out of the way location.
This is why using an IOT monitoring system, to detect the voltage of each of the three voltage supply wires, is useful.
Current being drawn by motor
Each Induction Motor will have a manufacturers specification for how much current is drawn, both at startup, and when fully running.
For more information on induction motor monitoring , get in touch.
(c) Craig Miles 2015-2020. All rights reserved. www.craigmiles.co.uk @acraigmiles
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