I just got to come incontact to semiems soft starts and seem to like like it. I have no idea how it works but I see a need for them replacing regular starters that start across lthe line. Can they be used to replace starters that serve pumps/ motors 10-40hp ? Are there any draw backs to changing to soft stats?
Soft Starts
- Thread starter jimbo123
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kingpb
Senior Member
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- SE USA as far as you can go
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- Engineer, Registered
Yes, there are drawbacks, and unless you need a reduced voltage starting for the specific application, or to help lessen the impact on the electrical system during starting, there is no need for them. Your maintenance costs will increase, and if they are starting a load which requires high starting torque, you could have problems. The bottom line, they do not work for every situation.
dbeasley488
Member
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- Suwanee, GA
Softstart application
Softstart application
Typically, soft starts are 2x the expense of an across-the-line starter. I usually don't call for soft starts until much higher motor sizes. Depending on what type you use, the soft starter can introduce harmonics into your system.
Softstart application
Typically, soft starts are 2x the expense of an across-the-line starter. I usually don't call for soft starts until much higher motor sizes. Depending on what type you use, the soft starter can introduce harmonics into your system.
kingpb
Senior Member
- Location
- SE USA as far as you can go
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- Engineer, Registered
Sure you arn't thinking of VFD's?
Yes, but during the starting period only.
After that they are either fully phased on or commonly bypassed.
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- San Francisco Bay Area, CA, USA
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- Electrical Engineer
Maintenance costs will increase? That flies in the face of everything published about soft starters and my overall experience with them over 20+ years. True they are not for some applications, but in general, no reason not to use them on pumps. In fact a lot of utilities now require RV starting at HPs as low as 15, although they will often grant variances for 15-40HP somewhat easily. Still there are benefits to using soft starters on pumps that might make it beneficial to not bother asking for the variance anyway IMHO. Soft stopping of pumps can be very beneficial in reducing or eliminating water hammer, which seriously increases reliability.
kingpb
Senior Member
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- SE USA as far as you can go
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- Engineer, Registered
Maintenance I was thinking, was for the SS device itself.
I agree they have there place for certain applications, to reduce water hammer would be a good reason to use them. Just have to be cautious as they are not one size fits all.
I agree they have there place for certain applications, to reduce water hammer would be a good reason to use them. Just have to be cautious as they are not one size fits all.
- Location
- San Francisco Bay Area, CA, USA
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- Electrical Engineer
We don't disagree on applications. Too many people expect miracles.
But maintenance on a solid state device? No moving parts on the soft starter, bypass contactors never make or break FLA, they end up lasting virtually forever. I have taught many classes on soft starters, here is my take on repairs / maintenance.
In an electromechanical contactor, what can go wrong? A bad coil or welded / worn contacts. So if it doesn't work, you have basically two things to troubleshoot and possibly replace. If a soft starter quits working, it can be a shorted SCR (equates to a welded contact) or a bad circuit board (equates to a bad coil); still only two possible things to replace. Better yet if it is a bad SCR, the controller usually tells you as well! Granted, shorted SCRs are not as easy to replace as a set of contacts, but they don't "wear out" either. If they don't get hit by lightning, they can outlast most of us living today.
It's not necessary to troubleshoot a PC board down to the component level, it's rarely worth the labor time any more; just swap it out. Most manufacturers make that very easy now; plug-in terminals, keyed receptacles etc.
kingpb
Senior Member
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- SE USA as far as you can go
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- Engineer, Registered
I will have to default to your expertise. My experience with them is much more limited and possibly segued to earlier generations of devices. I would agree that after determining it is a bad SS device, you simply replace the whole thing.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Just to clear up a very common misconception, Reduced Voltage starting of any sort (Soft Starter, RVAT, Y-Delta etc.) does NOT reduce your electrical bill in 99.99% of installations. People misconstrue that they will "save on peak demand charges" but that is true only in the rarest of utilities. 99.99% of utilities charge for peak demand based on a sliding demand window of 15, 20 or even 30 minutes. Any instantaneous peak within that window has almost no tangible effect on the overall peak reading.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Caveat to the above:
I have seen instances where, by installing soft starters on machines normally left running idle during breaks, operators went ahead and shut them off instead, figuring that they were not going to make the lights dim / re-strike on re-start. So indirectly, people CAN save on overall energy consumption and possibly on demand charges by doing that.
I have seen instances where, by installing soft starters on machines normally left running idle during breaks, operators went ahead and shut them off instead, figuring that they were not going to make the lights dim / re-strike on re-start. So indirectly, people CAN save on overall energy consumption and possibly on demand charges by doing that.
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