Help with a 3 phase star delta motor

[Knobhead]

From what I remember if the links in the motor terminal box are in a straight line across three terminals its star...if the links are arcoss two terminals each link its delta.
Running in delta will get the max out of the motor.

That is Star
Delta there will 3 links

 

[malcolmsanford]

Thanks for everyones help on this.

Just one last question. if one of the windings had failed could this cause the motor to run slower ( if it was running on 2 phases instead of 3) or would it not run.

Also i have noticed that the last electrician has swapped the yellow and red phase over in the bottom of the contactor. would this cause the fan to run slower.

I am back out there on monday trying to sort things.

i will try and swap the windings from star to delta first

then if nessarcery i will wire it as star/delta.

The fan has taken out the overload after around 20mins of running a couple of times. the overload is set at 5A at the moment so i have incresed this slightly. what could cause this.

alos the fan that it is running is around 2.5foot wide

If you lost a winding and as long as it was not shorting to earth then that could make the fan run slower. Easy to check just test all 3 windings and see what values you get.

Swaping over the phase will just change the direction of the motor it will not affect the speed it runs at.

If the motor is not runing at full speed ie "labouring" then it will increase the amps, like a water pump if you over design it's capacity ie you need to deliver 50 litres per minute but fit a pump that will deliver 500 litres a minute it will trip out on over load.

 

[jpmiff]

Hi

no need to run the motor in star delta, check the current the motor pulls on each phase, the o/load unit for the motor would trip with an out of balance load and the motor would get hot if the motor was two phasing.
if the fan needs to go faster have a look at an invertor

 

[Knobhead]

To be brutally honest I really don’t think you’re competent to carry out this work! I don’t think you have the basic concept of a 3 phase motor.
Sorry

 

[sheriff78]

No motors arent what i specialise in. I specialise in stage lighting and testing. the last time i dealt with motors was 14 years ago at college. That is why i have asked for the help and support of people who do. If everyone did the same then maybe we wouldnt have so many bodge jobs out there.

 

[Marvo]

Capable of doing the job or not is your decision at the end of the day. To me it sounds like you know enough to work safely so if the job is outside your skill set it could just work out expensive if you damage the motor.

Whatever you decide to do with the installation as long as the motor is running within it's specified run current on the info plate and as long as the current draw on all 3 phases is within 5% of each other then you shouldn't cause any damage further to what might have already been done.

 

[silva.foxx]

Firstly, a 5.5kw motor on 3ph 400v will draw approx 11 amps FLC so the overload, at 5 amps is undersized. Ensure your overload can be set to 11 amps.

The motor, according to the nameplate, should only be connected in either star Y

or delta

If it's a dual voltage motor then it'll be 400v Y, if a bog-standard 3ph motor more likely delta but confirm that with motor plate. If you connect it incorrectly you'll soon smoke the motor.
I'm sure you do understand that the connection has no real-life function as a speed control. If that motor is a 1500rpm motor then changing from star to delta will not change the speed for use.

Of course, you can use star-delta as a starting method only, not a speed control. The 'slow' speed in star-delta is the reduced torque building up to overcome the inertia of the load.

To reiterate the two-speed motor possibility (albeit unlikely) this utilises the star and delta connections to alter the usage and connections of the windings... but lets forget this option now.

Finally as one of the posters mentioned... bell the motor windings out then ensure you are getting full voltage through the DOL to the motor. Good luck. Please let us know what you find.

.

 

[Steve1412]

That is Star
Delta there will 3 links

I know thats why I said 'the links will be across two terminals each!!!'

 

[sheriff78]

I have belled the windings out and they all came out equal at 4.6 ohms. The motor is currently wired in delta. I think the customer has given me so duff information which has confused things.

I was told that it used to run faster until the last electrician came in

They forgot to mention that.

The motor has been removed and rewound since then

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

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

The belts are to tight

maybe it was rewound differently to the original.

These are all things that would of been nice to know a little earlier

If the motor is daul voltage how would this be marked on the plate?

thanks

 

[silva.foxx]

If a dual voltage motor the plate would be similar to;

220-240/380-415v Y/D... so 220-240v ie. off a 1ph inverter would be connected in delta else 380-415v in star. 4.5 amps in delta. 2.6 amps in star.

.

 

[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?