OT: Intelligent soft start

the_msp

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Haven't done much with soft starts, more-so VFDs' in my time.

Looking at replacing 3 x 37KW (415 V 50 Hz) star-delta starters with soft starters, but I'd like some degree of intelligence such as current feedback on 4-20 etc.

Any recommendations?

Going to site Monday to measure up, will chat to my Yaskawa rep then as have good relations with him.
 
I'm not a fan of soft starts with internal bypass contactors. Especially not for motors which do more than a few starts a day. An external bypass is more cost and complexity, but much easier to replace if needed.

Pay close attention to the start / stop ratings. If you need a ramp stop, it counts towards the hourly start rating. If you can freewheel stop that gives you more starts.

I like the Schneider ATS48 and it has the 4-20mA out for motor current you want. The ATS22 I've had problems with.
 
I would give some consideration to just going with a VFD in that power range the cost difference is minimal and the vfd has so many advantage over a soft start
As was said an external bypass contactor is required and pay attention to the number of starts
 
GaryS did make me think of one other aspect as well which gets overlooked, which is power factor correction. Of course if you have star delta starters then this is either already catered for locally through capacitors per motor, or at the main switchboard with a power factor correction unit ( static var converter or switched capacitor bank). Or maybe it's not corrected at all, in which case it is worth considering dealing with as part of the replacement.

Converting to VSD may have benefits but comes with downsides too which a lot of people overlook, because VSDs are "easy"..

Increased harmonics
True Power factor reduced (even though displacement power factor may appear improved)
Increased risk of RFI and EMI if motor cabling not carefully considered
Motor failures if not suitably rated for inverter use or if long leads used without dV/dt filter
Additional losses due to the VSD in terms of heat and conversion efficiency. Only a few % but that can add up on a motor that runs 24/7, especially when there's no need to reduce speed.

The benefits of course are speed control if that's relevant, and for Pump and fan applications drives are often good ideas but run the numbers and work out payback period.

Sometimes even just the reduced starting current can result in savings on the utility bill, depending on how it's metered.
 
Thanks.

The application is hydraulic pump motors, so there is no requirement for speed control as such.

This is used at a shipyard. Once started, the pumps time out after 5 minutes of no activity on the hydraulics. An educated guess would be about 15-20 starts per day. Currently, there is SWA between the star-delta cabinet and the pumps, and the cable length is circa 5 meters.
 
I would switch to VDF and not think about softstarter.

The soft starter does not give an equal start if the load varies or if there is a different pressure on the system when the pump starts.
With VDF, you can control start-up (and stop) and get a smoother start-up.

Remember to change cables from drive to motor to shielded cable regardless of whether you choose softstarter or VDF due to electrical noise.

I normally use Danfoss VDF.
 
You don’t need to add the extra complexity and sensitivity of a VFD for a hydraulic pump.

Stick to a Soft Starter, but buy a good one from a major manufacturer and make sure it is rated as heavy duty. There are lots of cheap versions on the market that cut a lot of corners, then are OK for light duty pumps and fans, but not PD pumps like those used for hydraulics.

Yaskawa doesn’t make Soft Starters by the way, so your rep will try to talk you into a VFD…
 
Make sure to check that the Soft Starter switches all three Phases and not just 2. Some soft starters have one leg that is always live at full voltage at the output of the soft starter. I am not a fan of those.
 
From personal experience, I advice you to not use Schneider Altistart. Models that are in production now are very bad. As Saffa mentioned ATS48 was very solid, but I'm not sure it can be ordered now or maybe it can be ordered but not for reasonable price. Softstarter needs to be much cheaper than VFD.
 
From personal experience, I advice you to not use Schneider Altistart. Models that are in production now are very bad. As Saffa mentioned ATS48 was very solid, but I'm not sure it can be ordered now or maybe it can be ordered but not for reasonable price. Softstarter needs to be much cheaper than VFD.

You're right, it looks like the ATS48 is soon to be discontinued. ATS480 is the replacement model. Same footprint, same functionality, new look. Probably the same inside just with some obsolete chips replaced.

Danfoss and ABB both do soft starts, have used both for centrifugal pump operation and they were fine. As mentioned by jraef, go heavy duty rating for your application.
 

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