UL 1004-6
Standard for Servo and Stepper Motors
First Edition – December, 2009 \
Second Edition \
June 6, 2012
3.1 General
3.1.1 This Section replaces 31.2 and 32.1 in UL 1004-1.
3.2 Servo motors
3.2.1 The Rating and Temperature Tests are to be conducted at two points on the SOAC curve:
a) Maximum torque and zero speed; and
b) Maximum torque and maximum speed.
3.2.2 In each case, the motor shall deliver rated torque and speed with the input current not varying from
the marked input current rating by more than 10 percent, and the temperatures on materials and
components shall not exceed the values specified in the "Maximum Temperatures" Table (Table 32.1) of
UL 1004-1.
3.2.3 At the manufacturer’s option, the Rating and Temperature Tests may be repeated to verify
operation at the two points on the SOAC curve corresponding to supplementary forced cooling and/or
heatsinking.
3.3 Stepper motors
3.3.1 The Rating and Temperature Tests are to be conducted at maximum torque and zero speed
(holding) in accordance with the manufacturer declared operating performance envelope.
3.3.2 In each case, the motor shall receive maximum-phase excitation at full rated voltage and current.
3.3.3 In each case, the motor shall deliver rated torque and speed with the input current not varying from
the marked input current rating by more than 10 percent, and the temperatures on materials and
components shall not exceed the values specified in the "Maximum Temperatures" Table (Table 32.1) of
UL 1004-1. If the manufacturer’s specifications require the use of a specified heatsink, the specified
heatsink shall be used in conducting the Rating and Temperature Tests.
