tgstoll
Member
- Location
- Collierville, TN
Working in the elevator industry, we run into this question from the field quite often - what percentage of the traction motor's nameplate current should be used to size the motor conductors based on the Duty-Cycle Service Table 430.22(E)?
The way an elevator motor operates in its application, it is considered intermittent duty as the table notes. We will typically advise the field to use the 140% entry in the table to be most conservative. However, this has been questioned because the actual full load current is typically considerably less. This leads installers and design engineers to insist on using a smaller sized conductor. They also argue the motors we use are not continuous duty (which is true, see below) and the closest motor type in the table is the 30- & 60-Minute Rated Motor column. So, they also insist on using the 90% entry in the table.
Our motors are typically rated at an IEC duty of S5 (http://www.engineeringtoolbox.com/iec-duty-cucles-d_739.html). How does this IEC duty correlate to any of the four motor ratings shown in the table? Is there a plan to add the IEC duties to Table 430.22(E)?
All comments/clarifications/interpretations will be most appreciated. Thank you...
The way an elevator motor operates in its application, it is considered intermittent duty as the table notes. We will typically advise the field to use the 140% entry in the table to be most conservative. However, this has been questioned because the actual full load current is typically considerably less. This leads installers and design engineers to insist on using a smaller sized conductor. They also argue the motors we use are not continuous duty (which is true, see below) and the closest motor type in the table is the 30- & 60-Minute Rated Motor column. So, they also insist on using the 90% entry in the table.
Our motors are typically rated at an IEC duty of S5 (http://www.engineeringtoolbox.com/iec-duty-cucles-d_739.html). How does this IEC duty correlate to any of the four motor ratings shown in the table? Is there a plan to add the IEC duties to Table 430.22(E)?
All comments/clarifications/interpretations will be most appreciated. Thank you...
