Severe Duty Vs. Standard Duty

[robgrant3]

I am wondering what considerations need to be taken into account when installing a severe duty motor. Do the conductors need to be larger, does the softstart need to be a certain percentage larger?

I am working for a client who is running a 150HP GE motor, and running it under severe conditions. He is powering it with 480V through an Altistart 48C21Yu. The softstart will power up the drive, and run for a given amount of time, than the softstart suddenly kicks off, and returns to rdy state, and does not provide an error code. Does anyone have experience with this problem? We are pretty sure it is a control voltage problem, because it kicks out and returns to the ready state, which is exactly what happens when you cut the control power, and turn it back on. Thanks!

 

[rcwilson]

There is very little electrical difference between severe duty and standard duty motors. That terminology usually refers to a motor enclosure's ability to handle chemical attack or the robustness of the mechanical components like bearings. A severe duty motor usually has a high service factor, meaning it can handle an overload.

Electrically, there should be no effect on the soft starter. But the load could be severe or overloading the soft start. Check your amps and volts during startign and running and compare to nameplate.

Also check for loose wiring. Your first guess on control power blips sounds liek a reasonable thing to check.

Good luck.

 

[robgrant3]

We think it is attibuted to the lack of a shorting contactor, in conjunction with the hazardous environment, and an improper enclosure. Another day in the life.

 

[boater bill]

If there is no shorting contactor, then the SCR's will be carrying the entire running load current. It may be too much heat in the enclosure.

The motor whether severe or standard duty should be drawing the same amount of amps.