Soft start or vfd

i thought i described it. a large belt sander that starts with a big chuck of iron resting on it. 10hp runs at about 30@ but inrush at start is 185@

frequency of starts depends. you would have to stop it to check progress. could be done in one start or may take several. i could squeeze by with 4 starts an hour with the job taking about 5-15 minutes with all the starts

i'm thinking whatever i go with i should probably at least double the rating if not more. i assume a 20-30hp ss or vfd would not be detrimental
 
The SS does not need to be up rated, the AuCom is not limited to starts and is rated at 34A continuous. If going with a VFD, I do not see the need to upsize if it is not needed and there are some other limitations as to fusing and input wiring. If going with a 20 Hp VFD then I would skip the RPC.
 
with the SS how is the machine started? with the SS or is that just in series.

right now there is a foot switch that operates a contactor. it would be two monkeys with a football if both had to be switched at the same time
 
SS and VFD are in series with the input power to the motor power. A SS has a bypass which closes (pass through) after the soft start and the AuCom also have a ramp down speed (soft stop). With high centrifugal loads there is always the issue of stopping and dissipating the energy. With a VFD you would use an external braking resistor to help dissipate some of the energy. The SS as to wiring, you would need to look at the directions for each unit. They typically use 2 wire or 3 wire control similar to VFD's, depends on how they are wired into your application. Trigger voltage can be low or high voltage for the SS, VFD is low voltage per the inputs. Depending on the route you decide, Wolf Automation technical would probably be the best source of information for sizing and installing.

AuCom trigger.jpg
AuCom Specifications.jpg
 
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I would probably modify your machine to start the motor fee of the load, then engage the load.
Everything on the machine will thank you, hell your electric bill will thank you.
 
sdelivery said:
I would probably modify your machine to start the motor fee of the load, then engage the load.
Everything on the machine will thank you, hell your electric bill will thank you.
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can't work that way unless you want to lose some fingers or hands along with destroying the work piece. can't set a 50-300# (+) workpiece on a moving belt
 
well wolf tech knew absolutely nothing about soft starters and they didn't have the product or know when they could get it. (must be covid)
aucom rep tho' verified it should work although he said it was a 6-10 cycle per hour. (which is ok)
i ordered a SR33-41 from automation direct. their selection chart says it should work and was in stock so i'm told
fingers crossed
 
Larry$ said:
An air compressor should not be started under load!
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Not all compressors have an unloader valve, mine don't , so it always starts under load.
It looks like deakin's machine also needs to start under load.
 
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