Need some suggession ..about Star delta with soft start

[Platootod]

There is some circuit using Start Star - Run Delta together with Softstart (Motor 75 Kw) ..(Power circuit below)
May be can explore the idia for some project.
Could anybody give me some suggestion about this Power circuit please
How to calculate or select an appropriate Magnetic Contactor?
(2 type of magnetic contactor)
What is the difference between type 1 and type 2 of magnetic Contactor
How to calculate or select an appropriate overload relay?
K6 in this picture is essential or not?
(someone told me using for good protection.
Some circuit from some book use 3 overload (add more below main cB)
1. Without Softstart K1 + K2 +K3 + K4
K1 + K2 = MAIN CONTACTOR
K3 = STAR CONTACTOR
K4 = DELTA CONTACTOR
2. With Softstart
K2 + K4 + K5 + K6 on at the same time ( K1 & K3 OFF )


Thank you very much

 

[dandrade]

K6 in this picture is essential or not?

Yes K6. Not K5 delete K5, and use digital input run.

 

[elevmike]

We have taken the practice of wireing our soft starters inside the delta. The soft starter we generally use is from Magnatek . This starter is primarilly designed for hydraulic elevators but I've seen them on other applications using pumps etc..It comes with a fault contactor and is easy to set up.

Here's a diagram on how it's wired.

 

[tzbul]

(without softstart)... You can't have K3 & K4 ON at the same time.
YOU are gonna have a BIG NICE short circuit .

 

[stevez]

soft start AND star delta

I thought that the whole point of a soft start was to do away with using a star delta starter.????

 

[JesperMP]

Sawatdee platotood

What is it that you want to achieve ?

 

[ArikBY]

Platootod

What you show here is soft start circuit with star delta circuit.
You can wire it in away that if the soft start would not work the magntic
contactors will start the motor.and the oppsite way.
the contactors there for backup.
Is that what you want?
K1,K2,K3,K4,Can be use as Star Delta Starter,K5&K6 must be off.
When K2,K4,K6 is on K5 will start the soft start and K1 will be the bypass contactor.
The motor overload have to be nominal current/1.73
About contactors current that a different story.
We have in IEC 2 common motor starter curve.AC1 and AC3.

AC3 is the current for start inductive load.AC1 is the current for resistance load or when the contactor use only as conductor.
It just rull of thumb,You better refer to the manufacturer of the contactors.

75KW is about 140A
So when you came to chose contactor you need to know how it work.
K5 and K6 will never carry all the starting current pick.
K6 is on before the starting and K5 just start the soft start
So you need to put K5&K6 AC1-140A



The current through K2 and K4 is 140/1.73=80A so they should be
AC3-80A
K1 sould be AC3-140A
K3 should be one size lower then K4
I hope you understand this process of how to chose magntic contactor


All the best

 

[Platootod]

Thank you very much for all reply
Especially ArikBy , You gave me the answer that I want.
For Star - Delta circuit without Softstart (need for backup or standby if problem occur at softstart)
8 years ago, I met some big grinding (particle wood) machine .
This machine has 2 motor (100 Hp each) .When start by Star Delta circuit ..need to stop and start for 2 or 3 time before run
(accordind to high start current) otherwist main CB of factory will shutdown .(without softstart)
I post this thread for example (my purpose) for everyone who need to know
also, can share some experience from several people here too ..
as ArikBy has answer .( better than my lag English )
From my opinion ,I think we need to use Magnetic contactor type 2 that
fit for continuouse circuit.(may be for European name )For NEC..or America use AC..name(Can someone from Europe give me more detail about Type1 ,Type 2 contactor please)
Thank a lot again .

ArikBy ..you made me confident in this circuit.
(Toda Raba)
Platootod

 

[ArikBY]

Platootod
You always welcome (bebakasha)
BTW
Do you useing there American standard?

 

[Jiri Toman]

it make no sense

I agree with stevez, if you have soft start why do you need star delta
starting on top of it?????
The star delta starting is still used by some Companies for the reasons of economy, but as the cost of soft starters goes down there is no need for star delta starting that I can see!

 

[Platootod]

Dear Jiri Toman ,
Thank you very much for your's comment.
I agreed with you about Softstart.
However, in this circuit from the reason as ArikBy has explain
already,Start Star - Run Delta circuit for back or standby(only)
( If you work as a consultant of some factory and the manager need
some backup circuit for his machine ..you have to take care...not kidding)
Dear ArikBY, Shalom ....I have been training about Cim system in Meyorhof at telaviv University and visit there 2 times.So I know some word
Todaraba (thank you very much)

 

[JesperMP]

An YD-starter adds a lot of complexity. 6 wires to the motor terminals in stead of 3, 3 contactors, etc..

Why not just keep a spare softstarter ?
It will not be more expensive than an YD-starter.