Star Delta Starter Motor Is Not Running At Delta

What does your class notes/ lectures notes say? Surely this was covered somewhere in your schooling? If not, let the rest of the world know what school you attended, so that no one else make the same mistake.

i think you know very well about the schooling.

If it makes you feel any better, I still have 6 hand written notebooks, 4 inches thick(US) and and the full array of micro cassette tapes of lectures I recorded from 35 years ago, that I refer back to.

So, yes I know about schooling

Dj95401, rating system is playing up change good answer rating to off topic.

I can't answer your question because I'm not a motor guy, but there are very skilled people here who can and will make an honest effort to answer your question. Hang in there and don't be put off by some of the comments. Someone will show up who'll be happy to help.

Is this a new installation?

If yes, who wired it up and commissioned it?

Is this an old installation that once operated properly?

If yes, what has changed?

this is old installation ,

we using this motor since 7 months ,

first it is good running,

since yesterday this problem came up

Do you have another starter on hand that you could swap in? Possibly a contactor isn't engaging or its contacts are burnt out? Just throwing out ideas.

we don't have another starter ,

but i check the contactors using multimeter they are good and also engaging.

Can you disconnect the controller from the mains and measure the interphase resistance in both star and delta configurations, eg, the stator winding resistance as seen through the controller from the mains input end? From your current measurements it looks like it should be working. What does the circuit look like 'from the mains perspective'? Is it symmetric between the three phases?

See #17⇓.

See #17⇓.

So, what's your first clue?

its great to hear sir ,

thank you sir for your suggestion

Just guessing, but maybe there is a current protection device (Fuse or similar) that is bypassed in the start configuration (allowing high amps for motor start) but causes motor to stop in delta configuration if it's blown.

Otherwise it's a loose/broken wire (or connector) in the delta set-up.

If it was running OK till a couple of days ago, then it points towards a specific component failure.

Are there other motors on the same circuit?

Have they shown similar symptoms?

no motors on the circuit only one motor connected

we check the current relay and fuses of all protection devices , all ok

motor amps reading know in star 57 amps later it will decrease to 13.67 amps after changeover to delta, flashes 21 amps and later its reading 13.45 amps.

but as per motor specification in delta it has to read <22 amps.

See #17⇓.

thank you

here the motor spec is 380 v, rpm 3480 , amps 22 in delta,

but know the motor reads the 13.45 amps in delta and speed is 3000 rpm +/- 2%

in star 13.65 amps reading

• <...star delta starter motor is not running at delta...>
• <...the motor reads the 13.45 amps in delta and speed is 3000 rpm +/- 2%...>

Those two things cannot both be true at the same time.

first 1 is not true but the second one is true in star it runs when comes to delta it not attaining the required criteria.

i just mistake on forum title

<...attaining the required criteria...> Attainment is the wrong concept. What is stated on the motor plate, and in the specifications for the motor, is the maximum current that the motor can withstand; that figure is what needs to be set on the overload protection device.

Mechanical load and current consumed are inter-related; if the mechanical load is such that the current consumed is much less than the maximum figure, then everything is fine apart from the possibility that the motor is over-sized for the duty.

Perhaps your power system is 50Hz frequency, not 60 as we in the US often assume. (380V should be a dead giveaway)

Thank you for information on measured motor speed.

Some thoughts....

1. You state motor is running at 3000 rev/min in what appears to be delta. With 3600 rev/min synchronous speed that is 17% slip.
2. At 17% slip a typical cage rotor induction motor would draw over twice rated current and deliver twice rated shaft power, say 45 amps.
3. Assuming the load is basically a fan with a Cube Law relation of speed to power then 13.5 amps X (3600/3000)³ = 22 amps near enough. Being a two pole motor with high power factor, the currents will be closely proportional to power. This accords with your expectation of 22 amps in Delta at normal speed.
4. If the motor is really in delta, I think only a big increase in rotor resistance can explain the high slip without high stator current. This is improbable.

I recommend measuring the voltage of the three windings at the terminals on the motor itself, in order to confirm the motor really is being connected in Delta. Please give the terminal letter/number codes you have the voltmeter probes on; for each of the three voltages you report. I am assuming 6 terminals at the motor - sometimes motors have two windings per phase.

I suspect that the 2 pole motor nameplate gives both 60Hz and 50Hz speed.

The motor speed is correct for 50Hz operation, and running lightly loaded

I don't understand how that would change the problem.....

The OP is complaining about the speed, really

https://www.ashleyedison.com/voltage-saudi-arabia-994/

Lists 127, 220 and 380V all at 60 Hz - another item, year 2010, mentions Saudi are standardising on 230V to match surrounding countries and 70% of world.

And OP Mohammed wrote in post #15 that motor is 380V, 3480 rpm. I thought that he would know that 3000 rpm versus 3480 rpm was significant.

No sure why you picked Saudi Arabia, but a quick survey from Wikipedia shows just shy of 80% of the 227 worldwide localities cited to be 50Hz. I was surprised it was not higher.

As to voltage, US & Canada are predominantly 480V and some 575V for this size equipment, 380V would be an outlier (copper hog), hence the valid question about frequency/location. The star-delta vs wye-delta was a phrase I had not picked up as being location specific, interesting observation..

Your motor when run in delta does not need to be full load at 22 Amp because your suction fan are couple with pulley and belts. I assume that most of the dust suction fan are driven by belts and pulley and since your motor are running at 3480 rpm it is not possible to have the fan direct couple to the motor with that high speed rotation. The full load current depend upon the dust suction fan load. Are your fan suction outlet damper are fully open or close? If the outlet damper are close then the motor current running at Delta will be less than the rated motor full load current.

Are you stating that a short time after the motor controller switches to delta connection, the feed trips, and the motor stops? OR does it simply spin down, or lock?

See #17⇑

Thanks.

Weird problem!!

That's just it. It isn't a problem.

As PWSlack said, you appear to be ASSuming that when in Delta, it should be pulling 22A. That is not true.

A motor draws current commensurate with the LOAD on the motor. In a centrifugal blower, load = flow. So if there is a damper in the duct or on the inlet of this blower, and the damper is CLOSED so that there is no flow, then there is no load on the motor.

I suspect that you are simply looking for a condition that is not valid.

wouldn't that be the inlet damper?

The blower doesn't care which side of it is restricted, it's still doing less work.

Fluid power is zero on closed damper. Shaft power in that condition is likely to be minimum (as with most centrifugal pumps) but not zero.

So you are saying that its stays in Star mode?

But there are several ways to switch over, some component in this "switch over" is possibly defective.

You/we need a wiring diagram of the starter, made as large as possible so that it is still readable here, or a link to a good online copy somewhere!!

See #17⇑

In Delta the motor do not run? In Delta if you lose 1 phase you lose part voltage over 2 windings and the windings will not be excited fully with only 1/2V across them. One of your phases do not switch on on the switch over from Star to Delta.

At first, Saudi standard is indeed 380 V and 60 Hz as 67model in #39 said.

In my opinion, at 3000 rpm the Y switch to Delta. The phenomenon is very fast and hard to follow well.

If the current in delta is still low now one has to clean the dust suction filter, I think.