Preventive maintenance programmes are the key to reliable, long-life operation of electric motors. Whilst AC Induction Motors are particularly reliable in service, almost all electrical equipment requires periodic planned inspection and maintenance. Planned preventative maintenance ensures electrical motors, and starters are kept in good working condition at all times. This is critical for businesses that rely on electric motors. A scheduled routine of motor inspection should be carried out throughout the motor’s life. Periodic motor inspection helps prevent serious damage to motors by locating potential problems early.
Planned electric motor maintenance programmes are designed to help prevent breakdowns, rather than having to repair motors after a breakdown. In industrial operations, unscheduled stoppage of production or long repair shutdowns is expensive, and in marine shipping environments, a potential safety issue. Periodic inspections of motors are therefore necessary to ensure best operational reliability.
Preventive maintenance programmes require detailed checks to be effective. All motors onsite (factory, ship etc) should be given their own individual identification (ID) number and have a record log. The record log is usually computerised these days. The motor records kept should identify the motor, brand, inspection dates and descriptions of any repairs previously carried out. By record keeping, the cause of any previous breakdowns can help indicate the cause of any future problems that might occur.
All preventative maintenance programmes should refer to the equipment manufacturer’s technical documentation prior to performing equipment checks.
There are simple routine maintenance checks that can be applied to three phase induction motors, which help ensure a long service life to a motor.
The Simple checks that can be carried out, include a review of the service history, noise and vibration inspections. Previous noise issues could for example be due to motor single phasing. Previous vibration may have been due to worn bearings, which allow the Stator to turn. Other checks include visual inspections (damage and burning), windings tests (insulation resistance & continuity), brush and commutator maintenance (dc motors) and bearings and lubrication.
Inspection frequency and the degree of inspection detail may vary depending on such factors as the critical nature of the motor, it’s function and the motor’s operating environment. An inspection schedule, therefore, must be flexible and adapted to the needs of each industrial or marine environment.
(c) Craig Miles 2019. craigmiles.co.uk
For bespoke electrical training with Craig, call +44 (01522) 740818
Railway Global System for Mobile Communications GSM-R
The railway Global System for Mobile Communications is also known as GSM-R & ‘GSM-Railway’. GSM-R Global System for Mobile Communications) is an international standard, covering railway communications. It is a sub-system of the European Rail Traffic Management System, or ERTMS . ERTMS is used for communication between trains and the railway control centres. The ERTMS system is based on the EIRENE – MORANE standards specifications. The EIRENE – MORANE specfications guarantee that the system will operate, at train speeds of up to 310 mph / 500 kph, with zero communication loss. Communication Security GSM-R offers secure voice and data communication amongst railway staff. Users include train drivers, engineers, station controllers etc. Communication security is important, both for commercial and security reasons.
Communication Hardware Components of a typical GSM-R include the base station, mobile units installed in trains, and handheld units. Antenna masts, connected to the base station are installed close to the railway track. Tunnels present a communication challenge, due to blocking and attenuation of the RF signals. The solution used, is to either use a directional ‘yagi’ antenna, directed through the tunnel entrance, or to use a ‘leaky feeder’ type antenna. A Yagi antenna when used as a transmit antenna, directs most of the Rf power in one direction, rather than in all directions. The Yagi antenna works similarly, when operating as a receive antenna, in that it receives most of the signal from the direction it is pointing in. A tv aerial on a house roof is a common example of a receive Yagi. The other solution for tunnels, is the ‘leaky feeder’ antenna. The leaky feeder is like a long piece of coaxial cable, which is designed to emit & receive RF (Radio Frequency) signals along its length. This allows communications to take place in tunnels and underground stations. The Leaky Feeder antenna is used in underground stations, where radio communications are required. The advantage compared with the Yagi antenna, in such locations is that leaky feeders can be positioned round tunnel bends. As Yagi antennas operate on frequencies that provide ‘line of sight’ signal transmission, bends will affect the signal path, attenuating them at best, blocking them at worst. The spacing distance on the surface between the base stations, is 4.3 – 9.3 miles (7-15 km). The system is built with high levels of reliability and redundancy built in, and if communication is lost, the train will stop.
The GSM-R specification standard forms part of the European Rail Traffic Management System, or ERTMS. The ERTMS is comprosed of the following parts: European Train Control System (ETCS) Global System for Mobile Communications – Railway (GSM-R) European Traffic Management Layer (ETML) European Operating Rules (EOR) Operating frequency band
GSM-R uses similar frequencies to the public mobile phone (cell phone) servcice, in most regions, namely around 900Mhz (E-GSM) & also at 1800 Mhz (DCS 1800). The exact frequency used by Railway operators, is dictated by national and regional regulation bodies, but the 900 Mhz & 1800 Mhz bands are used worldwide.
Induction motors are used widely in factories and on ships.
They are very reliable machines, but faults can develop over time.
That is why you need Induction motor servicing to be carried out.
Potential faults include burnt out Stator windings, worn bearings, and water damage which causes low insulation resistance.
This article covers tips on Induction motor servicing.
Safety & Isolation of supply of induction motors.
Correct electricity supply isolation procedures are critical for safety.
Taking a casual approach to electrical supply isolation can prove fatal.
Three phase Induction motors, typically operate in factories at around 400 Volts AC (Alternating Current).
Marine installations typically operate at an even higher 440 Volt Alternating Current (440 VAC).
It is important that no one works on a piece of three-phase machinery, such as an Induction motor unless you are qualified to do so.
On board ship, proper authorisation, such as a valid ‘permit to work’, signed off by a ships chief engineer, should be in place before carrying out any Induction Motor servicing.
On land seek authorisation from the responsible senior managers, with appropriate responsibilities for safety.
For work to be carried out aboard Ships, permission from someone such as the Chief Engineer is appropriate.
Once permission has been gained, and the appropriate paperwork issued, only then can work commence.
Certainly in the marine environment, and normally onshore as well, ‘locks and tags’ will be issued.
The lock is to ensure that once an isolator switch has been turned off, no one can switch it back on accidentally.
The ‘tag’ details who has isolated the supply, and is working on that circuit.
Only the person who has been issued with the lock and tag set, can remove them.
Double check that circuit is dead.
Don’t assume that just because you have locked and tagged the appropriate electrical isolator, that you are safe to work on a circuit.
The isolator may be incorrectly labeled, or even worse, you have taken someone else’s word for it.
Before you stick your fingers in, and potentially kill yourself, you need to use an appropriate device to check that the circuit is safe to work on.
Induction motor servicing can be dangerous, if proper procedures are not followed.
There are three possible devices that can be used:
Multimeter / Voltmeter
Firstly lets look at the test bulb as an option.
A test bulb with appropriate leads and clips attached, can provide indication of a live circuit, but has a flaw.
If the bulb filament breaks, then you could falsely assume that the circuit is safe to work on, with possibly fatal outcomes.
The second option is the Multimeter / Voltmeter which these days will probably be a ‘solid state’ digital type, rather than the older analogue types, which are commonly referred to as ‘AVO’s’ in the UK.
The Multimeter / Voltmeter being ‘solid state’ is more likely to be a bit more reliable than, a filament bulb tester. However it still may be broken, and you would not necessarily know. An example being the test probe wires may be ‘Open Circuit’.
The third option, the ‘Line Tester’, will provide the most reliable indication of whether a circuit is safe. Therefore this is the preferred option.
The reason that a line tester is safer is because it contains four separate Neon bulbs (some modern ones are LED).
The bulbs light up according to how high the voltage is, for example a 400 VAC supply would light not only the 400VAC light, but the lower voltage indicator lights as well.
So imagine that the 400VAC indicator bulb has broken.
The lower voltage indicator bulbs will still light up, for example the 230VAC and 110VAC indicator bulbs.
Therefore the engineer will still have an indication that there is voltage in the circuit, and can investigate further.
Before using a Line Tester you should use a ‘proving unit’. A proving unit is a small hand-held device capable of producing a voltage such as 250 Volts.
The Line tester can thus be tested using the proving unit, prior to testing a real live circuit.
To test the Line Tester the two probes are pushed against the Proving Unit which then produces a voltage.
This will be indicated by an indicator LED lighting up on the proving unit itself.
The Neon or Led indicator lamps of the Line Tester should also light up at the same time, to indicate the voltage being supplied.
Tips when changing bearings on Induction Motors
The bearings on an induction motor, allow the ‘Rotor’ to rotate inside the ‘Stator’ which surrounds it.
Over time they can become worn, which may increase noise and vibration of the motor.
Bearings are not usually adjustable, so replacement is required.
Importance of Bearing identification code facing outwards.
When refitting bearings to an induction motor you will notice that the bearing itself has a code written on the one side of it.
This code is the product identification code, and is what you need to quote in order to order the correct replacement bearing.
Once the correct replacement bearing has been obtained, and is ready for fitting, ensure the following.
Firstly, that the bearing identification code is facing away from the Stator, and outwards towards the end of the motor shaft.
This will help you in the future, if you ever have to replace the bearings again.
The reason for this is that you can just remove the end plate of the induction motor, and read the bearing code easily, provided it has been fitted with the code facing outwards.
If the bearing code was facing inwards, then it is harder to read the bearing code, and might mean that the motor shaft has to be disconnected from its mechanical load.
This adds to the motor downtime, and hence has financial and productivity implications.
Ways to remove bearings from induction motor shaft.
The ideal way to remove an old bearing from the induction motor rotor shaft is to use a bearing puller tool.
Removal is then just a matter of fitting, the tool into position, and winding in the screw thread in a clockwise direction.
As this happens, the bearing is slowly pulled up and off the shaft.
If however you don’t have a puller, other methods, such as using a metal bar to leverage between the bearing and the end of the shaft can be tried.
However this is not the way I recommend, and you do it at you own risk of injury and damage to the motor shaft.
Methods for fitting a new induction motor bearing.
Ideally you will have a hydraulic bench press, that you can use to put massive pressure down onto the bearing to ‘press it’ onto the shaft, in the correct position.
When using such a press, a number of precautions should be observed.
Firstly, ensure that you are fully competent to use the hydraulic press. Even fairly cheap versions are capable of exerting many tons of pressure, which can be dangerous to human health.
Secondly, ensure that the tube or sleeve that you fit over the shaft of the motor is only just wide enough.
The reason for this is that a wide metal tube (or sleeve) put over the motor shaft in order to push against the bearing, can damage it.
This is because too wide a tube will make contact with the plastic middle of the bearing, or the outer metal edge.
Both of these two scenarios are bad, because pressure applied to anywhere but the centre metal part of the bearing, will cause damage.
This damage can result in the replacement bearing being ruined, which defeats the object of replacing it.
Using a hydraulic press is the method that we would recommend, however this option is sometimes not available.
In particular to engineers working at sea in a marine environment, such as a cargo ship.
If you find yourself in this situation, then there are other ways to re-fit a replacement bearing to an induction motor.
One method is to take advantage of the fact that metals contract and expand due to cold and heat.
This method involves carefully wrapping up the Stator part of the induction motor in a polythene bag, and putting it in the freezer overnight.
This will very slightly shrink the size diameter of the bearing shaft.
The second part to the operation involves gently heating up a pan of engine oil, so that it is warm.
Obviously extreme care needs to be taken, so that either a fire is not caused by the oil igniting, or the engineer receiving burns while trying to handle the hot bearing.
Once the bearing is warm, the Stator can be removed from the freezer, and the warm oiled bearing should slip fairly easily onto the shaft.
The oil can then be wiped off the bearing with a non fluffy cloth, and motor reassembly can begin.
This blog post is about my design suggestions for an electric Morris Minor.
There have already been some prototype electric Morris Minor conversions already, which I will discuss.
In addition I have designed alternative ways to successfully convert classic cars such as the Morris Minor.
History & background
The Morris Minor is a British car designed by Sir Alec Issigonis, that was launched in 1948.
The Morris Minor originally was produced with an 918cc Side valve Petrol engine, but this was replaced in the early 1950s by an Overhead Valve (OHV) engine.
The OHV engine was improved and its size increased during the remainder of its production. and the later models were 1098cc in cubic capacity size.
The standard Morris Minor had the engine connected to a four speed longitudinal mounted gearbox, attached at the back of the engine.
The gearbox output is connected to a long single drive shaft, which runs underneath the car.
The drive shaft connects the gearbox to the rear axle.
The rear axle incorporates a ‘differential’ which fixes the speed ratio, between the rotational speed of the drive shaft, and the rotational speed of the road wheels.
Therefore as the engine power is transferred via the gearbox and drive shaft, to the rear axle, it is a rear wheel drive car.
Any design for an electric Morris Minor, will probably stick with the rear wheel drive configuration.
The reason for keeping the electric Morris Minor as Rear Wheel Drive, or RHD for short, is engineering design simplicity.
The front suspension on a Morris Minor was advanced for a British car of its time (1948).
The front suspension used torsion bars, as the springs, and featured ‘rack and pinion’ suspension, that is still used in modern cars.
The shock absorbers are different to the type used in modern cars, and are known as ‘lever arm shock absorbers’.
To convert an electric Morris Minor into powering the front wheels, known as front wheel drive, would require major suspension modifications (unless hub motors were used).
This is because the original Morris Minor steering and front suspension system, would need a lot of component changes.
Of course its possible to make a front wheel drive Morris Minor, but more expensive, and also changes the cars handling characteristics.
If however you are hell bent on a front wheel drive electric Morris Minor then its possible.
My solution would be to use hub integrated motors.
Hub integrated motors consist of an individual electric motor powering each driving wheel.
For instance to create a front wheel drive Morris Minor, you would have two motors driving each of the two front wheels.
If you wanted to use hub motors, but to keep the traditional Morris Minor rear wheel drive configuration, you would fit the motors to the two rear wheels.
So let’s decide to stick to the original rear wheel drive layout for our electric Morris Minor.
There are four ways that you could configure the electric motor layout. This also applies to many other classic cars, which share the same basic layout.
Firstly, the original internal combustion engine can be removed, whilst leaving the Morris Minor gearbox, driveshaft and rear axle (Inc differential) in place.
An electric motor is then attached to the original Morris Minor gearbox.
Some electric motor conversions that use this layout configuration, are clutch less in design. The torque & high rev range of many electric motors mean that the car can be driven in the same gear for most of the time.
Other electric car conversion designs still incorporate a conventional clutch.
The advantages of retaining a clutch are better motor speed control, and more importantly more retention of the original Classic Car experience.
A second option for mounting the electric motor in your Morris Minor, would be by removing the gearbox and either mounting the electric motor at the front end of the drive shaft, and directly attached to its front end.
Or alternatively the drive shaft could be removed, and the motor mounted directly to the rear axle differential input shaft.
This second method of attaching the electric motor directly to the rear axle differential connection, has advantages and disadvantages.
The advantage is a saving of weight, by removing the drive shaft which runs underneath the car, from front to back.
Less weight is a good thing for performance of your electric car.
The disadvantage is that it makes it a bit harder to mount, than if you mounted the electric motor at the front end, and retained the driveshaft.
It is harder to mount, because you need to create a mounting cradle which attaches to the rear axle, and supports the weight of the electric motor.
Morris Minor Hybrid
You may well of heard of Hybrid cars.
If not, then let me explain what they are.
A hybrid car is a car that uses a combination of combustible fuel, such as petrol or diesel, and electric power.
A hybrid car might drive the wheels using an electric motor at low town speeds, and petrol at higher speeds.
Alternatively, the petrol (or diesel) motor could be used, if the battery was low on charge.
The use of electric motors at low speeds around towns, has obvious environmental advantages.
However you might also still want a traditional petrol motor for long distance trips.
My design for a Morris Minor Hybrid, keeps the petrol engine, whilst also adding electric front wheel drive.
The rear wheels continue to be driven by the Morris Minors petrol motor.
Whilst the front wheels are driven by ‘in-hub’ electric motors.
A simple solution would be to have a manual switch, to be able to select the drive system.
Alternatively an automatic electrically controlled system could be used.
I am currently considering the design for an automatic system, and will provide further details in the future.
If you want design simplicity for your electric Morris, then keep the original gearbox.
The electric motor is simply attached to the gearbox, in place of the original petrol motor.
This is done via a special adapter plate, and a coupler.
The potential problem with using the original gearbox is excess motor torque.
Vehicle Electric Motors produce a lot of torque at low RPM (Revolution Per Minute).
The standard Morris Minor gearbox was designed to handle a maximum engine torque of 60 lb/ft (81 N·m) at 2,500 rpm.
The above torque figure is for the most powerful Morris Minor, built from 1962 onwards.
The gearbox was upgraded in 1962, along with the engine size (to 1098cc from 948cc), and gained Baulk-Ring-Synchromesh .
To ensure that you do not suffer premature gearbox failure, it is important that you consult electric motor manufacturers datasheets.
For an ordinary road going car, this should not be an issue, if precautions are taken to select a suitable motor.
For those looking to upgrade their Morris Minors performance, then this is definitely a consideration.
The Alfa Romeo (916) GTV was produced between 1995 – 2004, with only around 40,000 GTV models, and a similar amount of the open top Spiders, being manufactured during the whole period. They did not produce an electric Alfa Romeo GTV.
Reasons For Electric Alfa Romeo GTV
Reasons to convert a petrol Alfa Romeo GTV, or any Alfa Romeo to electric are both environmental and performance.
The smaller engined Alfa Romeo GTV, that was available to the Uk market, still emits 220 grams of CO2.
The smaller two litre ‘twin spark’ engine produces around 155 BHP.
Its possible to create a higher performing electric powered car.
The decision to re-engineer my own Alfa GTV, to run on an electric motor, rather than the original petrol engine, which emits a high CO2 level of 220.
I will be improving and updating this blog post on a regular basis, so check back regularly.
Why am I doing this? – Well for starters there is the high CO2 level.
The car failed its MOT in December 2012 on emissions and a small hole on the underside inner sill.
The car was put into my garage shortly after, and almost forgotten about, until recently.
Although I have successfully managed to get the engine going, the car would need a new rear exhaust silencer, radiator (as in poor condition), and new cambelt and balancer belts (not a cheap job).
The last items, are the main reason I took the car off the road after it failed its MOT in 2012.
The belts need replacing every three years, or 36,000 miles according to Alfa Specialists, and mine were way over due (time wise).
A second reason for wanting to convert my Alfa Romeo GTV to be powered by an electric motor is performance, yes you did read that correctly.
The Alfa Romeo GTV came in two basic variants, four cylinder, and six cylinder (V6) petrol variants.
The original 2 litre four cylinder version that I have, is a fantastic high revving motor, with a unique Alfa Romeo 8 spark plug design.
However it gets overshadowed (unfairly in my opinion), by the tyre shredding V6 version.
My objective is to create an Electric Alfa Romeo GTV that has faster acceleration, than the V6 versions.
But aren’t electric cars those off looking slow things, that oddball eccentrics drive? Electric cars have come a long way in recent years, due to advances in technology.
Just look at the acceleration figures for a Tesla Car, if you have any doubts.
Smart factories improve automation and efficiency compared to traditional factories.
Efficiency is increased both through process decisions being made without human intervention.
Efficiency is also increased by using sensor data to monitor the condition of machinery, such as three-phase induction motors.
Monitoring of induction motors, can include vibration sensors, which monitor the condition of the rotor bearings. A worn bearing will cause increased running friction, which can be monitored by attaching external vibration sensors to the motor casing.
Other conditions that can be monitored on a factory induction motor, are rotor speed, Stator winding temperature, single phasing faults, current drawn and voltage levels.
Other uses of smart factory monitoring systems, are the monitoring of the production process.
Smart Factory Buildings
The factory building that houses the operational machinery, also forms part of smart factories.
Automated temperature control has been around for years, and is also used in almost every home too. Its called an automatic thermostat!
Smart buildings can adapt the heating control automatically, by sensing where heat is needed in the factory building.
For example sensors, can detect if people are working in a particular section of the factory.
The sensor data is used to only heat the parts of the factory that require it.
The use of sensors can also be used to switch lighting on or off, depending on actual real-life demand for light, within sections of the factory.
Smart control of lighting and heating systems within the factory environment, reduces the variable costs of the the business operation.