looking for star delta motor starter diagram

[avz]

Hi
I'm looking for a wiring diagram of a star delta motor starter for my compressor. it's got a 5.5 hp motor and it has to be controled by "dry contact" from the presostat. if you have such an application circuit diagram - I know it's made of contactors and it's not pure electronics - that will be a great help.
Thanks.

 

[Reloadron]

You can have "star" also known as WYE or you can have "Delta" also known as triangle but you can't have both in the same place doing the same thing as far as I know. Both refer to a 3 phase circuit so what is the voltage? I assume 3 phase correct? Preostat? I assume a pressure switch so when the compressor tank drops below a pressure it will turn on the compressor and bring tank pressure up to a set point? Yopu would only need a 3 phase contactor with a coil voltage of your choice. What exactly do you have and what exactly are you trying to do?

Ron

 

[carmusic]

here an example of it, it takes 3 contactors to do it.
**broken link removed**

 

[Reloadron]

here an example of it, it takes 3 contactors to do it.
**broken link removed**

That drawing makes no sense, where did it come from? It's a 3 phase reversing configuration of sorts I think. If you want to run a 3 phase compressor (compressors are not reversing) you use a single 3 phase (3 line) contactor. The OP doesn't give a location so no clue what mains voltage is but you start with contactors similar to these. You also allow for thermal heat risers to shut down if the motor draws excessive current.

Ron

 

[bryan1]

I used to use a star/delta switch to switch on a 100 hp motor for a machine I was using, onday I heard some funny noises so I told the foreman to get the sparkies to check the motor. Due to the company winding back there wasn't any sparkies left and I was told not to worry about it. One cold morning when I pulled the handle down to switch to delta a loud bang and a 10' blue flame shot out of the motor, across the planer bed and into a guys leg giving him 3rd degree burns. The motor apparantly blew a primary winding and had to be totally rewound.

Anyway go look at the secondhand machine sale houses and ask them, I'm sure they will have some tucked away and you'll get on for a bargin.

Cheers Bryan

 

[Reloadron]

Find a motor starter rated for your motor. It would be connected similar to the attached image. Without more information, this is as good as it gets. I really liked Brian's suggestion as to finding a motor starter:

Anyway go look at the secondhand machine sale houses and ask them, I'm sure they will have some tucked away and you'll get on for a bargin.

They can be had cheap. We have a big industrial supply surplus place not far from us and I love that place. It's like a technical junk Disneyland. On WEdnesday's they offer up free hot dogs and hamburgers at lunc time cooked out on grills.

Ron

 

[Boncuk]

That drawing makes no sense, where did it come from? It's a 3 phase reversing configuration of sorts I think. If you want to run a 3 phase compressor (compressors are not reversing) you use a single 3 phase (3 line) contactor. The OP doesn't give a location so no clue what mains voltage is but you start with contactors You also allow for thermal heat risers to shut down if the motor draws excessive current.

Ron

Don't say something doesn't make sense if you don't know about it. It even won't reverse a motor, unless you change phases, which I don't recommend reversing phases from star to delta operation.

The effect would be the same as reversing an engine of a fast patrol boat while moving at full forward speed.

That kind of drawing makes a lot of sense to me, since I saw it at every place where high current 3-phase motors were used, e.g. fans of 2.85m diameter for a wind canal.

Starting those motors directly (delta) a 100KW motor will blow a 1000A fuse right at start. Starting in star-delta sequence will reduce starting current.

The contactors shown in the circuit must not be closed all at the same time. For a star-startup contactors one and two (from bottom to top) must be closed.

As soon as the motor reaches nominal rpm contactors one (main contactor, already closed) and three must be closed and shortly prior to closing contactor three (200 to 500ms) contactor two must be opened. Contactor three will short the motor windings (X,Y,Z) for delta operation, enabling the motor to deliver full torque.

Another way to start a high power 3-phase motor is using a Dalander circuit. It works about the same as star-delta sequence, but a bit more complicated.

Boncuk

 

[Boncuk]

Hi avz,

check out BBC, GEC, General Electric, Kloeckner-Moeller or Siemens for star-delta switches. There are no electronics involved using those.

Just select one for the required power.

The switches are supplied with a connection diagram.

Here is the example of a "Kloeckner" star-delta switch.

Boncuk

 

[avz]

Hi Boncuk
Thanks for the detailed explenation, but due to the fact that the purpose is to start an air comperssor - the option of a star delta switch, is not an option. I know that what I'm looking is not electronics, but I was hopeing that some of the members came across such a device's sechematic diagram. I'll keep on looking.

 

[Reloadron]

The reason I said it made no sense is there is nothing telling me the way the switches are drawn that the top and second switch down can't be closed at the same time. Yes, you can switch between Delta and Star closing the top or second switch down. Sorry.

The original post states: "I'm looking for a wiring diagram of a star delta motor starter for my compressor. it's got a 5.5 hp motor and it has to be controled by "dry contact" from the presostat". Again, sorry but I took it to mean a motor starter since it says motor starter? Damn, crucify me. I am sorry.

You can start a motor in WYE and you can start a motor in Delta but you can't have it both ways to start the motor.

Ron

 

[JimB]

You can start a motor in WYE and you can start a motor in Delta but you can't have it both ways to start the motor.

Yes... but with large motors it is common to start them with the windings in a star configuration, which significantly reduces the starting current compared with a delta configuration.
Then when the motor is up to speed, the configuration is switched to delta which allows the motor to develop more power than in a star configuration.

JimB

 

[Reloadron]

Yes... but with large motors it is common to start them with the windings in a star configuration, which significantly reduces the starting current compared with a delta configuration.
Then when the motor is up to speed, the configuration is switched to delta which allows the motor to develop more power than in a star configuration.

JimB

Absolutely Jim and I agree. I have seen it done with large high HP motors. I saw a 5 HP compressor motor and immediately discounted that. My bad on that note but never saw a 5 HP compressor that had a need to start then switch configuration. I am surrounded by 10 HP compressors at work, all delta and they start and run in delta. All 480 VAC. Anyway, again, my bad and sorry.

Ron

 

[Boncuk]

Hi avz,

to start 5hp motor (3.7KW) it won't require a star-delta start sequence.

All you have to take care of is making the compressor itself pressure-less (bleed valve) and start the motor directly (delta).

Those valves should be three-way valves being controlled by a pressure switch which closes the pipe between reservoir and compressor and bleeds the compressor during shut-down.

Starting a compressor under piston pressure the motor will take excessive current and probably it won't start at all but hum and burn up if not disconnected from power.

Boncuk

 

[Boncuk]

Absolutely Jim and I agree. I have seen it done with large high HP motors. I saw a 5 HP compressor motor and immediately discounted that. My bad on that note but never saw a 5 HP compressor that had a need to start then switch configuration. I am surrounded by 10 HP compressors at work, all delta and they start and run in delta. All 480 VAC. Anyway, again, my bad and sorry.

Ron

Hi Ron,

may be the OP doesn't want a star-delta configuration, but a schematic of how to wire the valves and pressure switches.

If he reads my latest post carefully and studies the sketch - I've made with pain using Eagle he'll know how to wire pressure switch and valve.

Please don't take my post personally. I didn't mean to offend you at all.

It was probably one of my mutual appreciation days when I responded.

Cheers

Boncuk

 

[Reloadron]

Hi Ron,

may be the OP doesn't want a star-delta configuration, but a schematic of how to wire the valves and pressure switches.

If he reads my latest post carefully and studies the sketch - I've made with pain using Eagle he'll know how to wire pressure switch and valve.

Please don't take my post personally. I didn't mean to offend you at all.

It was probably one of my mutual appreciation days when I responded.

Cheers

Boncuk

Hans, don't give it a thought. If I ever get back to Thailand I plan to look you up and enjoy a beer on the lawn on the roof.

Liked the cartoon.

Ron

 

[Boncuk]

Hans, don't give it a thought. If I ever get back to Thailand I plan to look you up and enjoy a beer on the lawn on the roof.

Liked the cartoon.

Ron

Hi Ron,

I bet you won't want to sit in direct sun light - namely in April, when temperatures rise to 46°C.

I'm not planning to plant trees on the roof.

Instead I offer you a shady place in the garden, cooled by waste air of my evaporative air conditioner.

"A" beer is singular meaning just one. "A" leg is also singular meaning just one.

Do you like to stand on one foot?

Which brand of Thai beer do you prefer? Beer Chang (elephant P) contains 6.4% (4 of them chemically produced), all other brands like Beer Leo contain just 5.4%. Beer Chang is preferred by Thais who are unhappy if they're not drunk after two bottles.

Always welcome for a visit.

Did you mean my simplified compressor functional "design" when talking about "cartoon"?

Regards

Hans

 

[avz]

Hi guys
Thanks for all your answers. the electric regulations in my country - Israel- are that motors of 5 HP or more, are to be started with a star delta or a "soft starter", that's why I want to hook up a star delta starter. btw, the compressor is equipped with a pressure relief valve on its pressostat, in order to prevent it to start under heavy load, just as Boncuk described. btw2 - the three phase voltage here is 380v.

 

[Reloadron]

Hi guys
Thanks for all your answers. the electric regulations in my country - Israel- are that motors of 5 HP or more, are to be started with a star delta or a "soft starter", that's why I want to hook up a star delta starter. btw, the compressor is equipped with a pressure relief valve on its pressostat, in order to prevent it to start under heavy load, just as Boncuk described. btw2 - the three phase voltage here is 380v.

Wow, I was in Israel during the early 80s maybe late 70s and never had a clue what mains voltages were but also never had a clue as to the use and starting of 5 HP motors there. Thanks for the enlightenment!

@ Boncuk

My first visit was in 72 for my R&R from Nam. Then later in the 70s. I loved Thailand and if I recall I was drinking Singha? Really not sure. When I was traveling extensively I loved checking out local brews where I was at. There were a few I liked as I recall. The food also. Hey, I love beer and food and when I travel I don't look for McDonalds and American Beer (which sucks)!

Oh yes, "cartoon" is a term my boss (manager) uses when he looks at my drawings which he is clueless about. I sort of picked the term up and sometimes use it. Yes, the compressor simplified design, which I really did like.

Ron