Motor over temperature 1

[Emadshaaban1987]

1800kw 6.6kv 3ph induction motor that has just arrived from rewinding by the manufacture .
During SOLO run test (no load ), the current consumption was 37A for each PH
But the RTD PT100 detected more that 100C for each phase and almost 50C for both bearing sides
What is the possible causes of the over temperature however the motor is running with no load and the consumption current is pretty good

 

[itsmoked]

The motor has an integral fan that's been correctly re-installed?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[RedSnake]

Motors usually have different isolation classes the lowest here are A then the motor can have a max temp of 105 C.
The highest H, max temp 180 C.

Best Regards A



“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[RedSnake]

With phase do you mean on the cables or the connection point or the windings?
Did you drive it in Y or D and for how long ?

We ones got a motor where they hadn't filled the bearing with fat.. but I think the bearings would have become much hotter if that was the case.

Normal standard motors are usually 130 C, max 155 C.

B.R. A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[electricpete]

180kw 6.6kv 3ph induction motor that has just arrived from rewinding by the manufacture .
During SOLO run test (no load ), the current consumption was 37A for each PH
But ...

The "But..." makes it sound like you're worried about the temperature.
But that current is waaay too high for no-load conditions.
What it the motor nameplate full load current?
Are you sure the motor is connected properly to the supply? (how many leads).
Is there any vfd involved?
What is the speed (affects expected ratio no-load to full-load amps).
What was current during post-rewind run at the shop (I'll bet it was a lot lower).
Double check your bus voltage is normal.
As RedSnake mentioned, this is a steady state current (not a startup current) correct?


=====================================
(2B)+(2B)' ?

 

[edison123]

FLC of 6.6KV 180 KW motor is around 18 Amps. Your no load current and winding temperatures are way too high. OEM screwed up the rewind.

Muthu

http://www.edison.co.in

 

[Emadshaaban1987]

I mistaken the size of motor,it is 1800kw not 180kw
The motor is driven under SEPAM protection relay.voltages are good and current are low.
The motor was working around 70c before rewinding.

 

[electricpete]

haha, yeah that makes more sense.

Some things to ask the rewinder:
What did the rewinder measure during their run at the shop?
If it ran hot at their shop
[ul]
[li]Ask for their core loss test before and after burnout.[/li]
[li]Make sure they have used magnetic wedges if that was in original design (that's a rewind problem we had that caused temperature to go up).[/li]
[/ul]Of course there's a lot more the rewinder can do wrong, but that's a start.

And one other thing to check, did the RTD's read roughly what you expected before the motor started? (to try to rule out instrument problem).

=====================================
(2B)+(2B)' ?

 

[edison123]

For 1800 KW motor, the no-load current of 37 A is too low unless it's a two pole motor.

If the rewinder uses burn-off method to remove the old winding, that could damage the core lamination insulation and would account for high core temperatures (at no-load, it's only the core loss since the winding copper loss is small). The rewinder is responsible for the jump from pre rewind 70 deg to post rewind 100 C in no-load. The no-load temperature rise is from 20 to 30 deg C only.

With the present high temperatures, the stator winding will fail prematurely.

Muthu

http://www.edison.co.in

 

[waross]

Do you have a Wye winding connected in star?
Is the stator centered?
Has the air gap been increased?

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jraef]

Assuming they replaced the RTDs when they rewound the motor, might they have made a mistake in what they put in, like maybe they put in 10 ohm instead of 100 ohm? Have you checked your connections? A high resistance connection will result in a false high temperature reading. Did you recalibrate the relay to the new RTDs?


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

One coil in a group reversed?
A problem with the rotor end rings?
With both the rotor and bearings showing hot, I would suspect either an instrumentation error as suggested by jraef or excess heat in the rotor.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!