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Old February 11th, 2020, 10:48 AM   #1
Karsten
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Soft starter with forward/reverse?

Hello,

I am looking for a Soft starter with forward/reverse?

Frequency inverters of course have this function but I am looking for a soft starter.
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Old February 11th, 2020, 10:56 AM   #2
GaryS
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The only ones I have seen, use a Forward - Reverse contactor with the soft start
the problem would be with the leakage with the solid state components
it would be phase to phase short.
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Old February 11th, 2020, 07:12 PM   #3
thingstodo
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Quote:
Originally Posted by Karsten View Post
Hello,

I am looking for a Soft starter with forward/reverse?

Frequency inverters of course have this function but I am looking for a soft starter.
I`ve never heard of a reversing soft start.

I`d be interested if it takes less space than the starter and the soft start
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Old February 11th, 2020, 09:29 PM   #4
Gene Bond
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There are a few out there that can Jog reverse. They pulse the 1/2 waves in the reverse sequence

Emotron is one that comes to mind: https://www.emotron.com/products/softstarters/

Quote:
Slow speed and jog operations
Apart from ramping up and down the speed between zero and rated motor speed, Emotron TSA softstarters offer low speed operation in both forward and reverse without additional hardware. Slow speed or jogging forward or backward can be useful for aligning a load or having the motor running at low speeds for test or service purposes. Examples of applications where such low speed or jog operation is valuable are loading/unloading of centrifuges or mixers, or positioning feeding conveyors.
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Old February 12th, 2020, 02:08 AM   #5
JesperMP
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Never heard about the reverse jogging feature before.
But if you need reverse at full power, it is by nature impossible with a soft-starter.
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Old February 12th, 2020, 02:44 AM   #6
JesperMP
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Out of curiosity, I checked the higher end Siemens softstarters that we some times use 3RW44 and 3RW55. And they actually do have this function. They call it "creep speed in both directions of rotation". The lower end soft starters do not have the function.

Well, learned something today. Maybe I can use it in some application.
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Old February 12th, 2020, 05:26 AM   #7
Jasondelane
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SMC flex and SMC-50 have reverse
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Old February 12th, 2020, 07:21 AM   #8
chopin
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Is it not as easy as to use a relays to revers your phases depending on the requested motor direction
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Old February 12th, 2020, 09:29 AM   #9
Ken Roach
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ABB's high-end PSTX soft starters have a "reverse jog" feature; it's advertised as a way to do clog removal on pumps. Allen-Bradley SMC Flex offers 10% and 20% reverse "Slow Speed" as well.

But to actually run full speed in reverse, every soft starter I have seen uses external reversing contactors. Simple, functional, reliable.
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Old February 12th, 2020, 02:26 PM   #10
BITS N BYTES
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Quote:
Originally Posted by Karsten View Post
Hello,

I am looking for a Soft starter with forward/reverse?

Frequency inverters of course have this function but I am looking for a soft starter.

IMHO VFD's [Frequency Inverters]are a much better solution that "old style" soft starters. AND in most cases less cost and MANY suppliers. I wouldn't waste my time on soft starters anymore.
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Old February 12th, 2020, 02:44 PM   #11
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Reversing Starter Without Contactors

There are some reversing solid state starters which do not use contactors. They have 4 additional SCRs which, when turned on, reverse 2 of the phases. Of the total of 10 SCRs, only 6 are turned on at a given time. The extra SCRs and the firing circuits for them add significantly to the cost and reversing contactors are generally cheaper, especially for smaller horsepower units.
Here is a diagram of an Eaton Tru-Start 10 SCR reversing starter.
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Old February 12th, 2020, 05:40 PM   #12
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Quote:
Originally Posted by Vic View Post
There are some reversing solid state starters which do not use contactors. They have 4 additional SCRs which, when turned on, reverse 2 of the phases. Of the total of 10 SCRs, only 6 are turned on at a given time. The extra SCRs and the firing circuits for them add significantly to the cost and reversing contactors are generally cheaper, especially for smaller horsepower units.
Here is a diagram of an Eaton Tru-Start 10 SCR reversing starter.
Yes, I didn't know there were still some of the offered, or I would have mentioned it. Back a couple decades ago, they were cheaper than VFD's. Not so much anymore I imagine.


Quote:
Originally Posted by chopin
Is it not as easy as to use a relays to revers your phases depending on the requested motor direction
This would efinately cost more than a VFD

Quote:
Originally Posted by BITS N BYTES
IMHO VFD's [Frequency Inverters]are a much better solution that "old style" soft starters. AND in most cases less cost and MANY suppliers. I wouldn't waste my time on soft starters anymore.
Very true up to about 100hp. BUT, VFD's are not as robust when you have generated power and other issues.
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Old February 12th, 2020, 06:51 PM   #13
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Several soft starter mfrs have, or used to have, 5 pole reversing soft starters. But it has fallen out of favor because it will end up costing more than just adding a reversing contactor, and they tended to be less reliable because people tended to try to abuse them, then short the SCRs. I'm not aware of anyone that still makes a fully solid state reversing soft starter. Benshaw and Motortronics both had them and ceased production. That "Eaton" one mentioned above was actually a brand-labeled product from a Canadian company called SAF Drives called the "SS6", which was an offshoot of the old Saftronics. That product is long obsolete. I believe SAF still makes Soft starters, but they no longer make the SS6 with the Reversing option.
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Old February 12th, 2020, 07:06 PM   #14
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Quote:
Originally Posted by Gene Bond View Post
Yes, I didn't know there were still some of the offered, or I would have mentioned it. Back a couple decades ago, they were cheaper than VFD's. Not so much anymore I imagine.




This would efinately cost more than a VFD



Very true up to about 100hp. BUT, VFD's are not as robust when you have generated power and other issues.

A VFD is a far more complex device. Fewer components and functions should equal superior long-term reliability for a soft start vs. a VFD.
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Old February 12th, 2020, 09:18 PM   #15
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OK - I learned something!

I don't expect that the new soft starts fixed the OTHER big issue ... 30% - 50% of rated torque on start?
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