Help with a 3 phase star delta motor

[Marvo]

I think the customer has given me so duff information which has confused things.

Par for the course.

I was told that it used to run faster until the last electrician came in ..........The motor has been removed and rewound since then........maybe it was rewound differently to the original.

The speed of the motor is determined by the number of poles and the supply frequency. It's very doubtful a re-winder would change the number of poles because a six pole motor requires a bigger stator to physically fit them in than a four pole motor.

also the fan unit is supposed to be cleaned regulary but this has not been carried out.

If the motor is bifurcated you can drop the belts from the pulley and rotate the blade by hand, this will give a basic indication if grease build-up is causing the blades to drag and causing a possible motor overload.

Could the problems with speed be that the load is to much for the motor.

If the motor was overloaded and was running in 'slip' condition then the run current would be way over it's allowed maximum.

The belts are to tight

It's unlikely that the belts being too tight will cause electrical overload of the motor, this would however result in high bearing run temperatures leading to premature bearing failure.
Motor overload is more likely to be caused by the blade angle being too steep or incorrect pulley ratios resulting in the blade rpm being too high.

Is it possible they installed the pulleys the wrong way around putting the larger pulley wheel on the motor shaft instead of the fan shaft??

 

[sheriff78]

If this is the case. How would you achieve the two different speeds. would you need an inverter

 

[sheriff78]

Thanks marvo. I am out at the job doing some other bits tommorow so i will get all the information of the motor plate, My reply was to the post before, just incase it didnt make sense

 

[silva.foxx]

If this is the case. How would you achieve the two different speeds. would you need an inverter

Yes.
A 1ph inverter would give you 3ph 240v out to be connected in delta.
A 3ph inverter would give you 3ph 400v out to be connected in star.

Is there really an issue with speed? Or is the customer just saying it used to be faster?

.

 

[malcolmsanford]

Thanks marvo. I am out at the job doing some other bits tommorow so i will get all the information of the motor plate, My reply was to the post before, just incase it didnt make sense

If your like me sheriff78 an installation sparks that as done a bit on motors then we are struggling. I can only say with dealing with customers they will tell you only what they want you to hear, in other words he most likely wants you to get a silk purse out of the sow's ear that is his motor.

You may have to bite the bullet here and get someone on site like silva.foxx amd Marvo who know what they are talking about and know their stuff to see if it is possible to speed up this motor. I know by theory that fitting smaller or larger pullies speeds up and slow down the speed that the fan turns, but to an installation sparks that is just theory, it's those guys that do this all the time that will know how to do it.

In an earlier post you noted that he couldn't get hold of the original sparks that did htis, that always to me is a sign that perhaps the customer is wanting something that can't be achieved and he is jumping around to see if he can find someone that will achieve it.

I may be wrong about that, but I still think that if your wanting to sort this out you may need the help on site of a silva.foxx or marvo.

 

[sheriff78]

I have copied down the information off the motor

EFF2

Brock crompton T-DA112MA NR=99281179

PHASE = 3
IP = 55
DUTY = S1
IEC 34.1
AMB 40 DEGREES C
COS = 0.84
CLASS F
WT 33KG
K36163

KW=4.0 V=300-420/660-720 DELTA/STAR A= 8.6-7.7/4.9-4.5 RPM=1445 HZ=50

KW=4.8 V=440-480/760-830 DELTA/STAR A= 8.7-8.0/5.0-4.6 RPM=1740 HZ=60

Can anybody let me know how this motor should be set up?

type of starter?
overload protection?
what size inverter if compatible?

Thanks for every bodys help with this

 

[silva.foxx]

I have copied down the information off the motor

EFF2

Brock crompton T-DA112MA NR=99281179

PHASE = 3
IP = 55
DUTY = S1
IEC 34.1
AMB 40 DEGREES C
COS = 0.84
CLASS F
WT 33KG
K36163

KW=4.0 V=300-420/660-720 DELTA/STAR A= 8.6-7.7/4.9-4.5 RPM=1445 HZ=50

KW=4.8 V=440-480/760-830 DELTA/STAR A= 8.7-8.0/5.0-4.6 RPM=1740 HZ=60 ----- forget this line as we're only on 50Hz.

Can anybody let me know how this motor should be set up?

type of starter?
overload protection?
what size inverter if compatible?

Thanks for every bodys help with this

This is the info we could've done with in post #1... the better quality of info given the better and more direct the answers...

So it's a 4kw motor.
400v Delta.
DOL starter.
Overload set to 8.5A.

or 3ph inverter with a rated output current of >7.7A

What size cables are supplying this motor and how long is the run?

Thanks for the info, sheriff, and for coming back. I find it annoying when people ask for info then disappear! Keep at it... you can sort this out. Let us know how you get on.

 

[sheriff78]

Thanks silvafox

The run is around 3m it is supplied in 1.5 singles

i havent managed to trace the circuit protection yet because nothing is marked in the db and everthing is being used so they dont want me to shut down. so i will be back in one evening next week to find the circuit.

The place is a total mess. I found one of lighting circuits wired to a c20 breaker and wired in 1mm!

how much will an inverter increase the speed of the fan by?

thanks

 

[silva.foxx]

Thanks silvafox

The run is around 3m it is supplied in 1.5 singles

i havent managed to trace the circuit protection yet because nothing is marked in the db and everthing is being used so they dont want me to shut down. so i will be back in one evening next week to find the circuit.

The place is a total mess. I found one of lighting circuits wired to a c20 breaker and wired in 1mm!

how much will an inverter increase the speed of the fan by?

thanks

No wonder they couldn't get hold of the 1st spark!

You have two options with this business. (1) Run away as fast as you can before the place burns down! Or... (2) Stay in contact, tell them all that is wrong with the place, hope they want the same and put right to sleep tight.

I heard a story once about a shoe company that sent two salesmen out to remote parts of thrid-world countries. One reported back "They don't wear shoes. No opportunities here.". The other reported back "They don't wear shoes so there's plenty of opportunities here!" - ramble over.

Inverter; theoretically you have a speed range of between 15-50 Hz but you'll have to consult fan manufacurers for fan speed design spec and see if you could exceed 50Hz. Ideally (but absolutely no chance) if the business has the original details of the spec and install you can progress as it saves a hell of a lot of guess work and inaccurate assumptions.

Just find the protective device, ensure the cabling and earthing adequately sized and installed, set the overload to 8.5A and get it going in DOL in the correct DoR (dir. of rotation). By fitting an inverter you will need a feedback device (such as a pressure sensor, moisture sensor, thermal sensor, pot, selector switch for preset speeds, etc...) to control speed.

As others have suggested above... is the fan sized for the job, perhaps further vents have been added adding air volume which now exceeds the fan sizing, etc. With it being an exhaust fan, perhaps the fan cowl is $hi.tted up and fouling the fan causing the unit to run overloaded and smoked the original motor.

 

[sheriff78]

I have suggested a full periodic on the property. I think the remedials will keep me busy for a while.

I also found a bunch of singles coming out of a conduit (3 circuits) one had a plug on the end and the other 2 where live! just piled up on the floor. This was all wired in new colours so it cant of been in more than a few years.

I will try and find out as much info on the ventilation system. The customer is still saying that it used to run slow for around 15 secounds and then it would speed up but i have no idea how this used to happen.

if an inverter is fitted and it runs at 60hz would this give the 1740rpm that is listed on the plate?

 

[TF and the wire]

Not had the chance to read every reply on this but it sounds like the reason it was running slower was because in star, it only had 230v on its windings which were designed for 400v. In effect it was almost stalling. Then when the delta kicked in, it had the full 400v and ran at its designed speed.
4kW motor is well able to be run of a DOL starter. If you didn't want to get another starter you could connect it in delta and connect the 3 cables to the load side of the RUN contactor (see the diagram on a previous page). Just make sure that the overload setting is within range about 8amp.
I wouldn't bother with an invertor unless the customer wants to vary the speed.

 

[remer1957]

I think that there's a bit of inexperience here-maybe you should have told the customer that the motor was sha**ed and that you would replace the whole lot as a new installation, then at least he is bearing the cost (it is a business cost), not you wasting your time trying to get the whole story out of him. IMO there is a line which you don't want to cross, otherwise you may become a busy fool. If this happens on a few jobs at the same time you would need overloads to manage. Also, a new installation is not always more expensive-it comes with guarantees and warranties, you can be sure the whole install will do what it says on the tin and he gets peace of mind for the future. If he does go elsewhere someone else can be a busy fool.