Motor Rated power vs require power

[Michael2009]

Hi friend,
I am not electrical person...
I am confusing about some data in motor datasheet.
We have a pump which have BHP = 344 kW. And Siemens induction motor will drive by 4160V 60Hz.
In vendor datasheet it show Nameplate power "min 380 @ 45 degC kW. and in other line of datasheet it show rated 420kW.


1. I Preparing load list. I should consider 380 kW or 420 kW as motor load?

2. I am confuse, why the motor plate is not mention 420kW but it shown min 380 kW and what is the 45 deg mean?

3. What is 420kW mean? is motor maximum rated power?

4. I try to check siemens motor model 1NB1 404-6AA30-4AA0-Z catalog, it do not have power rate 380kW or 420 kW. it only have 370kW, 400kW and 450kW. Not sure how they come out the rated power?

5. If I consider 380kW in my design load list and Switchboard design. What happen if the motor actual need 420kW to run?

6. All the time. I was thinking the motor nameplate shall stamp the rated power same in catalog. Even thought we all know it does mean will run to the level. Is this concept correct? or it should stamp the require shaft power for pump (motor output power)?

Thanks for clearing my doubt..

 

[7anoter4]

In my opinion, if the maximum output power at 45oC ambient it is 380 kW then the rated ambient temperature it is 30oC and the maximum conductor temperature it could be 130oC [B type insulation].Then at 30oC ambient the maximum output power could be 420 kW. See-for instance:

https://www.kollmorgen.com/en-us/bl...or-derating-due-to-high-ambient-temperatures/

 

[waross]

A picture of the nameplate would help.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Michael2009]

7anoter4 (Electrical)12 Apr 18 17:19
In my opinion, if the maximum output power at 45oC ambient it is 380 kW then the rated ambient temperature it is 30oC and the maximum conductor temperature it could be 130oC [B type insulation].Then at 30oC ambient the maximum output power could be 420 kW. See-for instance:

https://www.kollmorgen.com/en-us/blogs/_blog-in-mo...

ambient temperature go up, continuous torque will reduce and rating will go up?

 

[Michael2009]

waross (Electrical)12 Apr 18 21:03
A picture of the nameplate would help

I dont have motor plate photo..

 

[ScottyUK]

IEC motor ratings are generally stated at 40°C and at sea level. If you operate in a lower ambient temperature then you can wring a bit more out of the motor. If you operate in a higher ambient temperature then you'll need to de-rate the motor.

If you operate signficantly above sea level you will also need to de-rate it because thinner air found at altitude is less effective at cooling.

It's likely that the datasheet states the minimum requirements to drive the pump load at a given set of operating conditions, and then states the capability of the proposed motor at the same conditions. Provided the motor capability is greater than the demand from the load you should have no problem.

 

[Hoxton]

Please do not forget that the motor starting current is dependent on the rated current of the motor, not the load current...

It is common to select a motor rating higher than the required driven equipment power (pump, compressor etc). Some specifiers request a motor capability + 10% on required power. Then, as motors come in standard frame sizes, you can end up selecting an even larger motor.

 

[Michael2009]

ScottyUK (Electrical)13 Apr 18 05:36
IEC motor ratings are generally stated at 40°C and at sea level. If you operate in a lower ambient temperature then you can wring a bit more out of the motor. If you operate in a higher ambient temperature then you'll need to de-rate the motor.

If you operate signficantly above sea level you will also need to de-rate it because thinner air found at altitude is less effective at cooling.

It's likely that the datasheet states the minimum requirements to drive the pump load at a given set of operating conditions, and then states the capability of the proposed motor at the same conditions. Provided the motor capability is greater than the demand from the load you should have no problem.

that mean i have to consider 420kW in load list? and the motor nameplate should stamp 420kW ?

 

[Michael2009]

Hoxton (Electrical)13 Apr 18 07:57
Please do not forget that the motor starting current is dependent on the rated current of the motor, not the load current...

It is common to select a motor rating higher than the required driven equipment power (pump, compressor etc). Some specifiers request a motor capability + 10% on required power. Then, as motors come in standard frame sizes, you can end up selecting an even larger motor.

that mean 380kW is require mechanical power (motor output). So motor input is 420kW, load consideration is 420kW.
then my starting current shall be base on 420kW not 380kW...

my understanding correct?

 

[ScottyUK]

I am taking a guess that what you have is a motor rated at 450kW at 40°C per IEC 60034, but which de-rates to 420kW at 45°C.

You should select the thermal element of the protection based on the motor data for the operating conditions, so if this is a 450kW motor de-rated to 420kW for your ambient temperature then the thermal overload settings should be based on the de-rated values. The data should also state a locked rotor current, typically listed as a multiple of running current, which will allow you to correctly set the instantaneous element of the protection relay or to size the backup fuses if this is a contactor starter.

 

[Michael2009]

ScottyUK (Electrical)13 Apr 18 17:28
I am taking a guess that what you have is a motor rated at 450kW at 40°C per IEC 60034, but which de-rates to 420kW at 45°C.

You should select the thermal element of the protection based on the motor data for the operating conditions, so if this is a 450kW motor de-rated to 420kW for your ambient temperature then the thermal overload settings should be based on the de-rated values. The data should also state a locked rotor current, typically listed as a multiple of running current, which will allow you to correctly set the instantaneous element of the protection relay or to size the backup fuses if this is a contactor starter.

I actually confuse .. my supplier tell me, they normally stamp motor plate base on design rated of motor (Standard manufacture motor rated) instead of motor output) instead of output power rated. In this case, it will be 420 kW. but in their pump datasheet showing BHP = 344 kW. For me, 380 kW is the actual motor output power rated. this value shall be stamp on motor plate. So when we do load count will take this value consider efficiency and calculate the motor input power (actual load).

 

[panter]

It look me like 380kW motor with 1.1 service factor .

 

[ScottyUK]

Except IEC motors don't generally have a service factor in the way that NEMA types do.

 

[LionelHutz]

I'd tend to agree with ScottyUK. The motor is likely a standard 450kW design derated to 420kW @ 45*C. So, you likely have to size the feeding equipment for 450kW and then set the overload for 420kW.

 

[Michael2009]

thanks panter , scottyUK, Lionelhutz

I understand the whole picture now.
Pump BHP is 344 kW and API requirement 110% of duty. So is 380kW. Then motor standard size is 450kW and 420kW is derated value on 45 degC ambient.


Now i got 2 final question..

1. Normally in motor catalogue, we can see some standard range of motor, 8kW, 11kw, 18 kw.. 400 kW... this all is talking about motor output right? i mean motor mechanical power..

2. for my case, my motor nameplate shall stamp as 420kW @ amb 45 degC or 450 kW @ amb 40 degC?

 

[ScottyUK]

1) Yes, shaft output power.

2) Could be either. IEC 60034 uses 40°C as the default ambient temperature, so if the motor is built to IEC 60034 it will probably be plated as a 450kW motor, unless the nameplate also lists a non-standard higher ambient temperature alongside the rating at the non-standard temperature.