Duty Cycle Characteristics for DC Servo Motors

This paper describes methods of calculating the peak temperature rise of the armature winding of a dc servo motor when operated on a specific duty cycle and for torque values greater than rated. It also defines the relationship of the maximum allowable time ON (t
R
) for a desired output torque such that the peak temperature rise will not exceed the temperature rating of the insulation thus ensuring adequate insulation life. A new approach of specifying these duty cycle characteristics is suggested which can be used to find the maximum time ON (t
R
) for a given torque as well as the peak temperature rise for any length of time ON (t
1
). The use of these characteristics can be extended from repetitive cycles to duty cycles where output torque requirements within a cycle are varying. This analytical approach is supported by experimental data.