Correct calculation for Star Delta sizing - Contactor & Overload

Personally have no idea what y'all are saying.

The rule of thumb (theory etc) says a 60HP motor at 440-480 will be 1.5 amps per HP, that means it will be slightly higher at 415v, say 80 amps. I have no idea why that factor was divided by 2.

I do not see a specific reason to STAR start/Delta Run a 60hp motor overall, if it will run continuous for several hours at least.

If it is a cost evaluation I would not consider a star/delta or a softstart, just get a VFD, the ROI will be equvalent in most cases.
 
JesperMP said:
Hello Flyers.
Your prices for softstarters seems a bit high.
And the Powerflex is a VFD, not a softstarter.

We use the new Siemens 3RW40 range extensively now.
It is the low cost type, but with integral bypass contactor, so it makes for a very compact setup.
List price for a 200-460v 75kW (134A) 3RW4055-6BB44 is approx 1200 USD.
It is the smallest in this range with an integral bypass.

There is another lowcost range without the integral bypass 3RW30.
List price for a 200-460V 55kW (75A) 3RW3045-1AB14 is approx 750 USD.

If you add the extra panel space and wiring time, the softstarter is practically on par with an yD starter.
If your factor in that both contactors and softstarters are heavily discounted, then the panel space and installation cost weighs even more against yD.

Other manufacturers also have lowcost ranges.

Jesper,

I know PowerFlex is VFD, so it cost more, around USD5k++, while for Softstarter it's around USD 3k++.

USD3K++ still a lot more expensive than normal contactor. I'm comparing AB to AB products.

Thank you.
 

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