Document g5BR1GzL1EJjyL16QKDxbRxQ

R ^3- Milwaukee Brakes for the Proposed AISE #800 Motors Special Industries Development Mr. C. W. Warner, Manager July 2, 1965 This letter is a supplement to my letter of June 7> 19^5, . under the subject "Brakes for Motors Designed to New Stand ards". I understand that the'question has been asked whether the brake can be dropped one .frame .size (keeping the same torque) as is proposed in the change from the #600 to the #800 mill motors (keeping the same horsepower) . As pointed out in a discussion before I wrote the letter of june'7 there is that possibility; but a more logical solution from the design standpoint is to rearrange the sizes of brakes used with the motors. ' , Page 2 cf my letter of June 7 lists several assumptions made in analyzing brakes to be used with the #800 motors. Those assumptions still hold, but a more detailed explanation ' of section l.A. is now desirable. The NEMA brake standard IC 1-20.21 is primarily based on the PRESENT NEMA Industrial Control Standards parts 43 and 44 for Cab and Floor operating . cranes. These standards state tliat the electrically-operated brakes are to have sufficient torque to hold at least full load motor torque. Thus, in the present standard setup for the NEMA-AISE brakes with the #600 motors, the ratio of brake torque to F.L. motor torque ranges from 1.01 to 1.72.' I par ticularly stress the PRESENT standards which permit brake ,torque to be equal to F.L. motor torque because, since the letter of June 7 I received a copy of Mr. Thom's letter of June 4. In that letter he states t-hat NEMA is considering changing the Industrial Control Standards parts 43 and 44 to specify in part "The holding brakes for hoist motors with control braking shall have a rated torque of not less.than 150$ of the full lead hoisting torque at the point where the brake is applied". Note that this is not F.L. motor torque! I am quite sure that NEMA-AISE will set up brake torques based %,on a minimum percentage of F.L. motor torque rather than on a minimum of 150 full load hoisting torque. The following discussion is based on brake torque being not less than 100^ F.L. motor torque in accordance with present NEMA Standards. , ' I. Print SKO63065-I-AEL shows three brake combinations for each of the proposed #800 motors. . ` SCF-EC-1030 SC-EEI-0785 " fMSZ"