Square D "ATS48" Softstarter

[ayeinc]

Has anyone used this softstarter in an application in which you did not use the bypass contactor configuration. If so, will the softstarter provide current limiting during steady state running (i.e. not accel or decel)

 

[jraef]

Their older starters were NOT designed to be operated without a bypass contactor, but this one does say that you can with restricted ratings. Derate 2% for every degree of operating tewmp over 40 deg. C, and stay withing the operating parameters of a class 10 overload curve. Depending upon the unit size and ambient temperature, that may end up meaning moving an whole lot of air, and even though it may have fans on the heat sink, they are NOT designed to exchange the necessary volume of outside air to keep it cool. The cost of a blower and finding a place to mount it and a power source for it may be close to the cost of a bypass contactor, notwithstanding the long term operating costs.

Most soft starter current limit circuits remain active even when running, however as in this case, the lowest setting is 150% of FLA anyway. So about the only thing it is going to do is possibly make the OL take longer to trip on a locked rotor.

What are you trying to do with it?

"Venditori de oleum-vipera non vigere excordis populi"

 

[ayeinc]

I am working with a company from Germany that manufactures portable rock crushers. I have built one MCC unit utilizing parts (ie. Square D) that are more available int the U.S. than what they would notmally use if built in Germnay. In the past they used a sofstarter manufactured by ProSoft of Germany (

http://www.trippe.de).

The Germans insist that they need current limiting capability on the large crusher rotor. The ProStart seems to do this according to the Germans. I spoke with ProStart myself and they say it does this by simpliy not fire the thyristors. Most crushers use large rotors with high inertia, however the German design is to use a lower inertia rotor to keep weight down since it is portable.

 

[jraef]

I cannot imagine what they could possibly think to acomplish by using current limit continuously on a crusher. In starting, yes, but in running, no benefit whatsoever. I think that you may be confusing the two conditions. It is very common to use current limit starting on portable equipment because they are often supplied from portable generators, and the limited power source can be best accommodated with current limited starting. Having it current limit after it is at full speed would do nothing useful, and more likely would harm the motor or stall it at least.

Where the confusion may come from is that some soft starters are made very cheaply, and are Voltage Ramp only, or can only current limit for a very short time before they must go into bypass or at least full-on so that the SCRs do not overheat. Other heavy duty soft starters will allow the current limit function to override all other settings and stay in current imit until the motor accelerates or trips on overload. That may be what your ProSoft starter was doing, and that would be a valid issue. I do not know if the ATS-48 has the necesary capacity, but here in the US they are not used much on crushers and the like. They yend to get the pump and fan market.

"Venditori de oleum-vipera non vigere excordis populi"