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Limitorque Corporation

5114 Woodall Road o P. O. Box 11318 o Lynchburg, VA 24506-1318

Telephone (804) 528-4440 o FAX (804) 845-9736


UPDATE - 93-03

SUBJECT:       Reliance 3-Phase Limitorque Corporation Actuator Motors

               (Starting Torque @ Elevated Temperature)

REFERENCE:     Potential 10CFR21 Condition Dated May 13, 1993 (Attached)

                         Issued September, 1993

The purpose of this update is to provide guidance in addressing the

referenced document.

1.   550/575 Volt 3-Phase - The tabulated data presented in the

     referenced document is applicable to 550/575 volt, 3-Phase Reliance


2.   Motor Applicability - The tabulated data presented in the referenced

     document is applicable to all Reliance 3-phase motors.  The motor

     start torque, no-load speed, and frame size must match that given in

     the tabulation, e.g.:

          Existing Reliance 230/460, 3-phase, 60 Hz, 100'#, 1800 RPM, 210

          Frame motor design curve unavailable.  From the tabulation,

          percent current loss is 17.8 percent, and percent torque loss

          is 13.1 percent when subjected to a 155 degrees C increase in


3.   Deration Start Temperature - The torque reduction is to be applied

     at temperatures >40 degrees C (104 degrees F).  The tabulation

     details percent loss over a 155 degrees C change in temperature

     (i.e., from 25 degrees C to 180 degrees C).  The percent torque loss

     per degrees C for a 10'#, 1800 RPM, 56 Frame motor is:

               27.7%   =      0.179% / degrees C


               155 degrees C

     The percent torque loss for this motor operating in 100 degrees C

     ambient is:

          (0.179%) (100 degrees C - 40 degrees C) = 10.7%

4.   Temperature Rise With Motor Energized - Reliance 3-phase motors are

     designed with thermal characteristics that result in 

Page Last Reviewed/Updated Thursday, March 29, 2012