×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

What correction factor for - 4 deg C motor rating?

What correction factor for - 4 deg C motor rating?

What correction factor for - 4 deg C motor rating?

(OP)
Anyone can suggest what correction factor should be used for -4 deg C ambinet while selecting the AC motor?

RE: What correction factor for - 4 deg C motor rating?

What are you trying to correct?

RE: What correction factor for - 4 deg C motor rating?

(OP)
well i want to make sure that the torque is sufficient for clod start of the pump controlled by VFD?

RE: What correction factor for - 4 deg C motor rating?

I don't think a low ambient will reduce motor torque much, other than what is caused by the thicker bearing grease (assuming anti-friction bearings).

-4 deg C isn't all that cold anyway.  Any if you a have motor space heater, it wouldn't be -4 in the motor.

But I await correction from the motor experts.   

RE: What correction factor for - 4 deg C motor rating?

(OP)
Acutally the inside ambient temperature is -4 deg C and the motor should be rated ot -40 deg C. This is winter time and i think i should have high torque available for the motor for cold start?

RE: What correction factor for - 4 deg C motor rating?

Should be no problem.  You do need to worry about condensation on both the VFD and the motor or you could have zero starting torque.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

RE: What correction factor for - 4 deg C motor rating?

Is your concern actually that the torque requirements of the **load** will increase in cold weather?  That's a different question than the one you are asking.

RE: What correction factor for - 4 deg C motor rating?

Standard NEMA MG1 Part 14 defines USUAL SERVICE CONDITIONS.

Environmental Conditions
Machines shall be designed for the following operating site conditions, unless other conditions are specified by the purchaser.
a. Exposure to an ambient temperature in the range of –15°C to 40 °C or, when water cooling is used, an ambient range of 5°C ( to prevent freezing of water) to 40 °C, except for machines rated less than ¾ HP and all machines other  than water cooled having commutator or sleeve bearings for which the minimum ambient temperature is 0°C.

RE: What correction factor for - 4 deg C motor rating?

(OP)
Thanks Guys,
Yes as indicated by "dpc" torque is a concern do you suggets me to double the torque for cold start of pump?
becuase i have to select the motor for pump operating temperature in winter condition is -4 to -40 deg C?

RE: What correction factor for - 4 deg C motor rating?


this sounds like a freezer job

-20 degree F conditions
in my industry it is always standard practice to mulitply any hp requirments by 1.25  on top of any hp calc for motors.  This was due to things never worked at that low of temperature as they did above freezing.

Of course you have all the thin gear box oil that you need.  Then of course avoiding the use of compressed air unless you could gaurentee the dewpoint down to -20f.

RE: What correction factor for - 4 deg C motor rating?

(OP)
hi controldude,
thanks very much for your reply. Finally i worked with factor 2 to be on more safer side.

RE: What correction factor for - 4 deg C motor rating?

forgot about the thin grease you need also, but I think other responses pointed this out.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources