need help and opinion

[ajay34]

okiepc...i would glad to post the shematic drawing ..need to scan and i will post it here...
basiclly auto transformer are same as wyse delta starter only diffrent it has no star point contactor and the wyse done on auto transformer and it have tapping ..

can i ask ..is there calculator to calculate motor full load (fla) for starting ..mean without using clamp tester..j

 

[leitmotif]

here is the pic of name plate breaker and overload

Nuts you will ahve to go up to see the motor nameplate data.

1. Motor is built for 50 or 60 Hz so that is OK
BUT Running motor at voltage nominal 440 designated for 60 Hz BUT his line freq is 50.
I would consider matching name plate values ie motor connection voltage at 50 Hz.
AND on the 440 rating is that double symbol "wye delta" indicating wye start delta run?

2. Why the auto transformer? Uh what does it do for you ie as a variable voltage soft start or to adjust line voltage?
Are you able to set taps to achieve name plate values for wye connected at 50 Hz?

3. Relays look like wye start delta run. IF that is what you are doing -- is it even able to switch over to delta before tripping OR is it tripping because of the "changeover"

You may wish to consider a VFD to start this - yep wont be cheap.
BUT should let you reduce the starting current, tailor the VFD to teh motor specs, eliminate wye delta start (only gain here is greater simplicity - wye delta is OK if properly done). Would have to evaluate teh autotransformer and what he does and the need if any.

Dan Bentler

 

[ajay34]

1) there motor are connected on delta connection using 3 cable..

2) why auto tranformer..huh..well by using auto transformer i able too
required torge as well and surely yes by tapping that are current voltage i need to used to start before it kick too delta after 5 sec.

3) 100% it not wyse delta method ..if you look at the panel it have 2 motorl control 1 used for auto transformer and the other used wyse delta which are 2 diffrent motor as well..triping happne before it change to delta .
4) cant used VFD for thios pelletmill ..due to the start tourge and the kick should be very fast (whihc i hope u understand what i m trying too say ) i had used VFD beofre on other plant but seem not pratical ..so we switch back too soft starter and auto transformer.

 

[Gil47]

A rule of thumb for motors at 400 to 440 volt range at 50 Hz is 2 amps per Kw, this really only applies to under 20 KW, so as the KW output rating goes up, the amps required go down, so when you get to 160 Kw about 10 to 15 % reduction can be applied, mainly because the fan requires a lower % of the energy to do its job and newer motors have a higher efficiency.

So you should be using the top line on the motor label 420 v 50Hz 160 Kw 990 Rpm 273.6 Amps.

The over load of the motor should be taken back to 300 amps which is the lowest setting available on your overload as the motor full load amps is 274 amps.

A 160 Kw motor according to motor / fuse rating charts requires 355 amp fuses for direct on line or in your case 315 amp fuses for an assisted start a curcuit breaker would require similar settings.

I have worked on many auto transformer starters.
The right hand contactor should be the first one to close, followed almost immediately by the middle contactor, then once the motor is very close to full speed, Once the Ammeter shows a low amperage below 250 amps .

At this point and you say 5 seconds the right hand contactor will open, this removes the star point on the auto transformer.
Whilst current will still flows through the windings of the auto transformer for part of a second whilst the right hand contactor drops out, once that has happened the left hand contactor will close this is the main run contactor.

The Right hand contactor dropping out and the left hand contactor coming in will be almost the same time.

I believe you are saying that the motor breaker trips when it is trying to start.

My suggestion is to make sure the right hand contactor has not got any welded contacts.

Also I would shift the timer to say 10 seconds to make sure there is plenty of time for the motor to get up to speed and monitor the ammeter to see how the start reaction goes.

Do they try to start the motor with a load in the hopper

 

[Ned_Flanders]

I work in a milling plant with 75kw mills and a 160kw fan.

They are start/delta started. The 75kW mills are 3000rev/min and will draw 250 amps for AT LEAST 20 seconds before the current falls and the starter changes to delta.

The 3000 rev/min 160kw fan draws MORE THAN 400 amps while starting in star (AND we close off the air so it starts off load)again, probably for 15 - 20 seconds. It is fused at 355 amps.

I imagine starting in star gives a similar current reduction to a 60% auto transformer?

I think you mean your 400 amp breaker is tripping out rather than the overload device?

At what point does the breaker trip? Is it as the autotransformer is changing to delta run?

I agree: you need to increase the run-up time and monitor the current if you are sure the motor is not faulty.

 

[bce123]

ajay i had a problem once with a y/delta start on a compressor. i solved it by replacing the 400amp breaker with a new 400amp breaker that was rated 100%.this was a CH breaker in the panelboard. i agree with the time thing some times lowering it helps. but its like rocket sci u have to know when to fire the boosters o rentry Good luck, Steve

 

[ajay34]

I work in a milling plant with 75kw mills and a 160kw fan.

They are start/delta started. The 75kW mills are 3000rev/min and will draw 250 amps for AT LEAST 20 seconds before the current falls and the starter changes to delta.

The 3000 rev/min 160kw fan draws MORE THAN 400 amps while starting in star (AND we close off the air so it starts off load)again, probably for 15 - 20 seconds. It is fused at 355 amps.

I imagine starting in star gives a similar current reduction to a 60% auto transformer?

I think you mean your 400 amp breaker is tripping out rather than the overload device?

At what point does the breaker trip? Is it as the autotransformer is changing to delta run?

I agree: you need to increase the run-up time and monitor the current if you are sure the motor is not faulty.

yes you are rite it not overloading it triping ..
the breaker trip after start before auto transformer change to delta ..

here what happen ..i increase the run up time and ..it heat up the auto transformer and cut the temp safety thermal.

 

[ajay34]

ajay i had a problem once with a y/delta start on a compressor. i solved it by replacing the 400amp breaker with a new 400amp breaker that was rated 100%.this was a CH breaker in the panelboard. i agree with the time thing some times lowering it helps. but its like rocket sci u have to know when to fire the boosters o rentry Good luck, Steve

i steve i agree on that...i had ask qualify breaker tester to test the breaker and it been certificate as good condition instead i had repalce a new breaker with same size as well

 

[OkiePC]

i steve i agree on that...i had ask qualify breaker tester to test the breaker and it been certificate as good condition instead i had repalce a new breaker with same size as well

A good 1000amp clamp on meter with a peak hold function would probably tell you pretty quickly if the breaker is bad or undersized.

 

[Gil47]

yes you are rite it not overloading it triping ..
the breaker trip after start before auto transformer change to delta ..

here what happen ..i increase the run up time and ..it heat up the auto transformer and cut the temp safety thermal.

This quote above has me suspecting the operation of the right hand contactors operation either the contactor is not pulling in properly and creating the star point for the three windings of the auto transformer, this will cause an auto transformer to over heat quickly, as the windings operate more as a resistor with a small amount of choke operation.
or
the right hand contactor operation is keeping the star point in operation when it should have opened just before the main contactor comes in, this would cause a portion of the auto transformer to over heat at that time.

Are all three contactors operating as they should or as I described in my earlier post

 

[ajay34]

we had overcome the problme ..after changing the tapping too 80% and chnage the breaker too 600amp..it running back normal ..

would lik eto extend my thank full to all who had hint me and guide me ..
thank you so much