Industrial electric motors
Have questioned about industrial electric motor electrical connections before.
Had issue with loose connections causing arcing between terminals.
So consensus was check all connections in junction box so to reduce risk & put your name on it.
What other checks especially if motor burnt out for some reason before new or rewound motor powered up?
- insulation test with mega
- cable & lug condition
- all connections checked from starter & motor.
- direction test uncoupled
- thermistor checks
What else to reduce risk on a new or rewound motor, what is industry or your standard.
Motors could have
- star delta
- auto transformer
- soft starter
- VFD drive
Re: Industrial electric motors
On a failed motor, get an autopsy done to establish cause.
Renew power supply components as required.
Re: Industrial electric motors
We only deal with whatever is on the compressor side of the coupling.
When we are doing compressor overhauls, we advise the customer to also have the motor checked, and tell them we could call a company in for them, or we give them the contact details and they can call them in.
We are available to be the muscle to get the motor out of the ship, or to turn it on the frame so the proper people can get access to it, but we never touch the terminals. They have to disconnect it, and they will reconnect it.
When it's all back in place, we perform the rotation check, with the motor guys in place, then we do the alignment and re-connect the compressor.
All the electrical connections falls on the motor guys, while some of us are more skilled in electrical work and we have all the tools, we always call in the guys that do this for a living to cast the final verdict if something has failed :)
Re: Industrial electric motors
The first thing I loot for is the manufacturer.
all industries are flooded with cheap far east motors that not worth repairing regardless the size.
I do once in a while Thermal imaging inspection of industrial motors on pumps and compressors drives.
I always start checking the power supply for hot spots motor protectors an contactors. Then going down to the motor terminals an last is the bearing temp.
A worn bearing on a motor will change the position of the rotor so phase drawn amps will change as well causing heat in the motor which can lead to burn out without having the motor protector trip!
I always replace motor protector, contactor and cable glands on the motor terminals every time a motor is replaced.
To keep motors life long, always look for a better starting technic an reduce starting torque.
Vibrations are a big enemy of locked nuts and bolts, eliminate them as much as possible.
Cast iron motor cages are heavier but compare to aluminium cages, they don't expand as much.
Motors turning belts should have their bearings checked more frequent then direct drive motors.
The sound of electric motor should be smooth and even, if you hear a kind of "humming" that comes and goes, investigate the source, there is a vibration somewhere.
Belts can be a pain and a motor killer if they are not looked after an replaced on schedule, when a small part of a belt is missing, the result is blows on the shaft, shortening the bearing life.
Most important - keep your hands away from fast turning objects!!
Re: Industrial electric motors
A week ago I worked the SAB 233E overhaul, engine running 100% without problem, but as Tycho writes, we also send the engine for review to a specialized workshop, this ABB (2500kg) identified hidden problems and needs to fix more than negotiated. I'm not electrically based-I do not understand everything.
Then, the compressor + engine thus prepared works reliably for 30,000 hours.
Josef.
Re: Industrial electric motors
Thanks everyone for input.
Mainly talking about direct drive motors on screw compressors in these cases.
What used to be a simple thing seems very complicated these days with VFD & soft starter drives.
We experience premature bearing failures after motor serviced by motor repair shop & somehow it's our fault.
In some cases motor repairers saying to use specialized vibration analysis equipment to grease a motor bearing would you believe.
Our laser alignments are no good causing bearing failure.
Talk about grasping at straws.
Motors turn up after general repairs & tails very loose, had just been test run in their workshop 30 minutes away.
We have tried 3 major rewind/repair companies, all the same, full of excuses.
All of them want to repair/sleeve bearing end shields as they say motor bearing loose in it (Teco motors).
Agree replace motor after burn out, but a lot of industrial motors have long lead time if unusual frame size, or size.
To many parties involved sometimes, us in the middle of disputes.
Re: Industrial electric motors
I have the same feeling when the engine burns down, it's never 100%. As for bearings and VFD, I have already used ceramic bearings, it is very expensive, I think it is also reliable. I have engines with a ceramic bearing for about 3 years and there is no problem.
Josef.
Re: Industrial electric motors
Quote:
Originally Posted by
RANGER1
Thanks everyone for input.
Mainly talking about direct drive motors on screw compressors in these cases.
What used to be a simple thing seems very complicated these days with VFD & soft starter drives.
We experience premature bearing failures after motor serviced by motor repair shop & somehow it's our fault.
In some cases motor repairers saying to use specialized vibration analysis equipment to grease a motor bearing would you believe.
Our laser alignments are no good causing bearing failure.
Talk about grasping at straws.
Motors turn up after general repairs & tails very loose, had just been test run in their workshop 30 minutes away.
We have tried 3 major rewind/repair companies, all the same, full of excuses.
All of them want to repair/sleeve bearing end shields as they say motor bearing loose in it (Teco motors).
Agree replace motor after burn out, but a lot of industrial motors have long lead time if unusual frame size, or size.
To many parties involved sometimes, us in the middle of disputes.
On motors with VFD, at least one set of bearings should be insulated bearings (best is on the NDE) because if you use normal bearings you will get microscopic welding spots on the Normal bearings, which will lead to premature failure.
Another solution is to put a "brush" on the axle that leads to ground, but my bet is on insulated bearings when it comes to VFD.
On soft starters it shouldn't matter, because on soft starters, they are only active during the spool up, once it's at running speed it switches from the Soft starter to a running contactor and once it switches over, the soft starter is not supplying the motor with pretend currents anymore.
With star delta motors, once the motor has a certain size, it should only be started 3 times per hour, but that isn't to protect the motor, it's to protect the contactor from burning up.
Soft starters are the same as star delta 2-3 starts per hour unless you want to burn something up.
VFD, you need insulated bearings on the NDE of the motor, or a brush, this is because the VFD is feeding the motor with all kinds of weird currents, and in some cases this can lead to the bearings welding, with Insulated bearings on one end or a brush leading to ground, you are leading these weird currents away from the bearings and to ground.
If a motor supplier is saying that it is your fault, they don't know what they are talking about
Re: Industrial electric motors
I can explain the reason to use vibration monitoring equipment to grease bearings, although I did not do it.
We had a supplier come in to our plant to demonstrate a simplified version of a monitor. We greased the bearings and expected the monitor to reflect this.
Nothing changed when we added the manufacturers recommended amount of grease.
The factory had not filled the bearing chamber. I removed the end bells to verify this.
If we had only used the specified amount of grease on their schedule the bearing would not have received any lubrication for years. So I did it the way I always have, pulling the bottom plug and pumping grease until it appeared at the opening, or until I felt a small amount of resistance.
As to cheap motors, at least in smaller sizes, I starting buying motors from Taiwan. Stainless steel washdown motors that that ran forever and were replaced across the counter in warranty with no question asked. Cheaper and lasted longer than the U.S. built motors I used for years.
Re: Industrial electric motors
Hi Ranger
When using VFD's the grounding of the motor is very important, but often not done correctly. When the drive is controlling the motor speed the transient currents are led to ground . If the ground cable is undersize or incorrectly connected, then these ground currents will use the motor bearings as a ground path which arcs the bearings causing premature failure. I saw this several times in the field. I used to set up vfd's and fault find when at Danfoss but correct grounding of VFD's is very important for the safety of the motor. If you are getting motor bearing failures ,call in a VFD expert to check the installation for problems, or advise the motor rewinder that the motor is connected via an invertor who should be able to advise you if they suspect a set up problem
Re: Industrial electric motors
Quote:
Originally Posted by
RANGER1
Thanks everyone for input.
Mainly talking about direct drive motors on screw compressors in these cases.
What used to be a simple thing seems very complicated these days with VFD & soft starter drives.
We experience premature bearing failures after motor serviced by motor repair shop & somehow it's our fault.
In some cases motor repairers saying to use specialized vibration analysis equipment to grease a motor bearing would you believe.
Our laser alignments are no good causing bearing failure.
Talk about grasping at straws.
Motors turn up after general repairs & tails very loose, had just been test run in their workshop 30 minutes away.
We have tried 3 major rewind/repair companies, all the same, full of excuses.
All of them want to repair/sleeve bearing end shields as they say motor bearing loose in it (Teco motors).
Agree replace motor after burn out, but a lot of industrial motors have long lead time if unusual frame size, or size.
To many parties involved sometimes, us in the middle of disputes.
Ranger1👍 Its all come down to basics, if bearing is inserted in the motor shaft
With lot’s of hammering then the bearings will fail. The bearing has to to be sourced from a authorised supplier only. Bearing should be heated and motor shaft to be cooled when inserting the bearing on the motor shaft. Motor end covers to be heated and bearing on the shaft to be cooled when completing the assembly. It May appear a bit childish to explain everything in detail but every step matters. If there is a coupling in between the compressor & motor or a pulley mounted on the motor shaft to carry the belts then again the coupling/pulley to be mounted on the shaft by heating it and cooling the shaft, the load of the motor to come on the shaft end and not on the motor housing.
If all the steps are followed meticulously only then the motor will work trouble free.
Re: Industrial electric motors
Vikky
I think your post is 40 yrs. to late.
Next you will be telling us to heat the bearing in Whale Oil!
You are not talking to school children here.
Have you ever seen the new generation of motors used (Variable Speed 12 pole for instance.)
I suggest you read a few of the posters posts to lean at what level of expertise, the engineer /s you are talking to at!
Just what do you do!
Grizzly
Re: Industrial electric motors
Quote:
Originally Posted by
Grizzly
Vikky
I think your post is 40 yrs. to late.
Next you will be telling us to heat the bearing in Whale Oil!
You are not talking to school children here.
Have you ever seen the new generation of motors used (Variable Speed 12 pole for instance.)
I suggest you read a few of the posters posts to lean at what level of expertise, the engineer /s you are talking to at!
Just what do you do!
Grizzly
@Grizzly here I was not referring to some domestic fridge compressor which has inverter starter(which is based on variable frequency drive) I was talking about the fridge compressor motor driving a compressor of capacity of 20ton/70 kw of cooling capacity. I was also referring to the motor driving 221KW of air conditioning compressor with 8 cylinders’W’design. These compressors are mostly belt driven for the ease of inspection & maintenance. Here motor bearings are renewed using induction heaters as one of the recommended way of the SKF bearing maker.
Re: Industrial electric motors
Quote:
Originally Posted by
vikky1971
@Grizzly here I was not referring to some domestic fridge compressor which has inverter starter(which is based on variable frequency drive) I was talking about the fridge compressor motor driving a compressor of capacity of 20ton/70 kw of cooling capacity. I was also referring to the motor driving 221KW of air conditioning compressor with 8 cylinders’W’design. These compressors are mostly belt driven for the ease of inspection & maintenance. Here motor bearings are renewed using induction heaters as one of the recommended way of the SKF bearing maker.
Vikky,
We are aware of correct practices, as for motor rewind companies we expect them to as well.
I suspect motor rewinders are using cheap labour that may not necessarily mean qualified trades person (trained monkey).
We have tried 3 big name motor repairers/rewinders & none impress me, they can't even tell you what grease to use, question to hard for them, think we are stupid for asking.
They just send motor back, no instructions from them to cover themselves in this day & age of procedures.
They claim they have to connect, align, grease motor as we do not know what we are doing, yet if we buy new motor no problems.
Some motors have characteristics of there own, which we expect them to know as well, nothing is ever simple as it seems.
Re: Industrial electric motors
vikky
Wow.
I don't know what I have been talking about all this time on the forum.
If you think I work with domestic refrigerators.
Please.
Just bother to take a look at peoples profiles!
Incidentally yours is a bit vague!
Some of the huge Shorch motors I and others here come into contact with.
Cannot be rebuilt by anyone other than very specialised motor rebuild companies.
The good ones admit they cannot!
Grizzly
Re: Industrial electric motors
Quote:
Originally Posted by
Grizzly
vikky
Wow.
I don't know what I have been talking about all this time on the forum.
If you think I work with domestic refrigerators.
Please
8 cylinder recip. Wow.
domestics who in their right mind would get involved with them,I like meat not smarties
Re: Industrial electric motors
Quote:
Originally Posted by
RANGER1
We have tried 3 big name motor repairers
Hey,
I've heard of the big name guys subbing repairs to the bloke in the dusty shed - have they failed to retain expertise?
I have also heard of the Test and Analysis Centre (where not a single item gets tested, all the gadgets and instruments are only for show..)
I think the fancy words for it are "Spinning off the Synergies"
Re: Industrial electric motors
This old post of mine may still have some realavance?
http://www.refrigeration-engineer.co...-Load-of-Balls!
Grizzly
Re: Industrial electric motors
Quote:
Originally Posted by
RANGER1
Vikky,
We are aware of correct practices, as for motor rewind companies we expect them to as well.
I suspect motor rewinders are using cheap labour that may not necessarily mean qualified trades person (trained monkey).
We have tried 3 big name motor repairers/rewinders & none impress me, they can't even tell you what grease to use, question to hard for them, think we are stupid for asking.
They just send motor back, no instructions from them to cover themselves in this day & age of procedures.
They claim they have to connect, align, grease motor as we do not know what we are doing, yet if we buy new motor no problems.
Some motors have characteristics of there own, which we expect them to know as well, nothing is ever simple as it seems.
@Ranger1 This is what I am referring to( to what you have mentioned in your post) sometimes the big names in motor repairs thinks that their customers know less but we know the basics. Their ego comes in between.
Well! Thanks for sharing. I am here to pick good things from all of you senior members.
Re: Industrial electric motors
Quote:
Originally Posted by
Grizzly
Grizzly,
Thanks, a number of years ago there was a notice sent out from SKF that copy. Earnings were on the market copying packaging etc.
The people who copied these bearings must not be to bright, as would it not be better to copy something less demanding.
Obviously some bearing mob shut down a plant somewhere & gear was sold off.
I would try to paint a rock with gold paint or something, then sell it, surely easier than making a bearing that does not work real well, or steal some bearings then sell them.
