VSD and Star/Delta together 1

[Mark.H]

Hi All,
I'm new into this forum so apologies if this topic was already discussed in the past.
I'm supposed to draw a control panel which would include both VSD and Star/Delta motor starter. Baaically, the operator is acting on a selector switch with SD/OFF/VSD positions. Do you happen to have a schematic or wiring diagram? I'm unsure of how to implement it given the fact the VSD only needs 3 terminals from the motor but the Star/Delta requires connectiom to 6 terminals of the same motor.
Thank you very much
Mark

 

[itsmoked]

I feel for you Mark as that is just Stupid Deluxe.

For starters (pun intended), you need the motor wired in delta to the VSD.
Next, you cannot have the VSD live sourcing the motor and ever interrupt its connection to the delta connected motor or you risk blowing the output stages of the VSD.

With a hand switch someone could cycle rapidly between it all.

This means you need to include some sort of delay timers to retard actions from happening. Think about the VSD running at full speed and someone switches to OFF then instantly to SD mode. You need a delay that will allow the VSD to come to a stop and cease driving the motor then a contactor needs to disconnect the VSD. Then the system can switch to SD mode.

Management needs to go all in on the VSD or stick with the crappy SD method alone.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Mark.H]

Thanks Keith. Well, now I see why there is a request for a digital timer in the bill of materials. I suppose the client wants to make sure (as you pointed) that no harmful switching is applied when the motor is still running).
By the look of it, it seems there is no automated equipment that does this and I need to come out with a DYI solution?

 

[LionelHutz]

Instead of a timer, I tend to wire controls so the selection is locked until the motor is stopped. So when the selector is in VFD mode, switching the selector does nothing until the VFD and motor are stopped.

To wire connect the delta contactor after the main contactor. It should be obvious, but the star contactor is mechanically interlocked with the delta contactor and connected after the delta contactor.

Put a VFD output contactor beside the main and mechanically interlocked with it, which is fed from the VFD and wired to the output of the main. That way, you can only use either line power or VFD power for the motor.

The controls have to continuously energize the delta contactor when in VFD mode.

 

[Mark.H]

Hi Lionel

Instead of a timer, I tend to wire controls so the selection is locked until the motor is stopped. So when the selector is in VFD mode, switching the selector does nothing until the VFD and motor are stopped.
Very happy not to use the timer. How can I implement that? Not sure how to "block" either VFD mode or Star Delta mode until the motor has stopped.

To wire connect the delta contactor after the main contactor. It should be obvious, but the star contactor is mechanically interlocked with the delta contactor and connected after the delta contactor.
Yes, that should be ok. I will connect a supplementary contactor to the VFD accordingly, which will ensure to maintain the delta configuration for the whole time the selector is on VFD mode.

Put a VFD output contactor beside the main and mechanically interlocked with it, which is fed from the VFD and wired to the output of the main. That way, you can only use either line power or VFD power for the motor.
So VFD and Star Delta mechanically interlocked in a way that either VFD or Star Delta are engaged. I suppose this condition is not mandatory in the event I use a supplementary contactor for the VFD Delta, correct?

The controls have to continuously energize the delta contactor when in VFD mode.
Clear that

 

[waross]

Google zero speed switches.
These often are used on conveyors and belt drive applications to detect belt slip and blockages and jam ups.
This is your best proof that the motor has stopped before being re-started.
I would consider a check circuit as well. When the motor starts, use the change of state of the zero speed switch to prove operation of the zero speed switch and latch a permissive relay for the next start.
(If this is a homework problem, you may get extra marks for showing this as an alternate solution. That depends on your instructor. Use your best judgement.)

But we are all wondering:

VSD and Star/Delta together

WHY?

This sums it up well:

I feel for you Mark as that is just Stupid Deluxe.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[che12345]

Dear Mr. Mark.H
Q1. "....I'm new into this forum ....I'm supposed to draw a control panel which would include both VSD and Star/Delta motor starter. Baaically, the operator is acting on a selector switch with SD/OFF/VSD positions. Do you happen to have a schematic or wiring diagram?...."
A1. Please tell us a little more the reasons WHY/WHAT are you after; stating that "...the operator is acting on a selector switch with SD/OFF/VSD positions " If you are a technical school or a test lab to illustrate/study the difference between SD and VSD, then we can understand. It is "unusual?" in the industry to have this configuration.
A2. It can be done, though rather complex. If it is for [redundancy] purposes, it would be much cost effective to have two separate individual SD starters with output connected in parallel?, but the incoming MCCBs shall be mechanically and electrically inter-locked. Caution: the idle unit is LIVE !.
A3. In marine application, the steering-gear system requires two separate starters and motors supplied from two separate sources; from different boards.
Che Kuan Yau (Singapore)

 

[Mark.H]

Hi Bill

Google zero speed switches.
These often are used on conveyors and belt drive applications to detect belt slip and blockages and jam ups.
This is your best proof that the motor has stopped before being re-started.
I will. That sounds good.

I would consider a check circuit as well. When the motor starts, use the change of state of the zero speed switch to prove operation of the zero speed switch and latch a permissive relay for the next start.
I will have to process this info and check how to implement. I'm a newbie in electrical design.

(If this is a homework problem, you may get extra marks for showing this as an alternate solution. That depends on your instructor. Use your best judgement.)
I would love this to be school bit it's actual work. So I hace to come out with a solition in order to get the job done

But we are all wondering:
Quote (OP)
VSD and Star/Delta together
WHY?
Very good question. No idea. Never seen such a system myself

This sums it up well:
Quote (itsmoked)
I feel for you Mark as that is just Stupid Deluxe.

Agree with you all

 

[jraef]

As to the "why" question:

Very often, especially on larger motors, the power system is more than capable of handling the relatively gentle acceleration current profile of a VFD, but may not have enough behind it to be able to start the motor Across-the-Line (DOL) if the VFD must be bypassed for maintenance or repairs. So they need some form of Reduced Voltage starting to accomplish that. Star-Delta is a common and well known form of RV starting, it is just (IMHO) the worst choice.; But it may be the only thing they know or trust.

I have done dozens and dozens of packages like this using Solid State Soft Starters as the bypass for the VFD, it is very cost effective, simple and the motor wiring does not need to change. The added complexity of trying to do this with S-D would make it untenable in my opinion. I would be suggesting that they use an RVSS Soft Starter instead. It will likely cost less as well.

Either way, you need to have MECHANICALLY INTERLOCKED contactors on the outputs of BOTH systems to prevent either from energizing the other backward. Doing that with S-D would require a PLC to keep all of those contactors straight and even then, I'm not sure you can mechanically interlock enough of them to absolutel;y endure safety. Again, way WAY too complicated.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[itsmoked]

One thought for all this is to make the S/D verses VSD switch a locking switch that only maintenance has or electrical or someone who has the ability to "switch" like the shift supervisor. This would prevent an accidental or 'entertaining' or 'for the hell-of-it' or 'hold my beer' selection event.

The VFD dies. Everything comes to a stop. The user hunts down the guy with the key and certainly nothing will be getting switched quickly while the VSD is still powering things.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

Parallel the selector switch with aux contacts from the VFD and FV starter along with some other wiring so the selector only works until either is started. There is one case this doesn't help, switching from FV to VFD mode with the motor still coasting. But, you can set the VFD to catch on the fly so it hopefully re-starts OK.

I'm not sure you understood my post. A main full-voltage starting contactor from line power and a VFD output contactor from the VFD output interlocked together. Connect the outputs of both together. Hook the wye and delta contacts up to this output. Ensure the delta contactor is closed in VFD mode. Operate the wye-delta starter as they typically work via the timer in full-voltage mode.

Having the contactors mechanically interlocked is not mandatory, but VERY, VERY, VERY highly recommended.

 

[itsmoked]

Yep very recommended.
And Mark the SD is the specified need for that parts-list timer.

Things to ponder in this mess:
There is typically a bunch of assignable outputs on the VSD. Assign one to indicate no output power. It will be a relay that you can use in the chain of permissives to allow the SD hardware to operate.

Further use one of the scads of assignable inputs (which you will need to relay isolate the VSD's controls voltage {24Vdc} back into it's own input) to tell the VSD "coast off". On newer VSDs they have Safe-Torque-Off which completely guillotines all drive output instantly and safely for the VSD. You can instead use that when the switch is in OFF AND SD mode.

You can sketch up your insanity and post it here and we'll critic it if you'd like to. We could probably all learn from this Stupidity Deluxe.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Mark.H]

Hi Che Kuan Yau

A1. Please tell us a little more the reasons WHY/WHAT are you after; stating that "...the operator is acting on a selector switch with SD/OFF/VSD positions " If you are a technical school or a test lab to illustrate/study the difference between SD and VSD, then we can understand. It is "unusual?" in the industry to have this configuration.
It's an actual project at work but never dealt with both VSD AND star delta.

A2. It can be done, though rather complex. If it is for [redundancy] purposes, it would be much cost effective to have two separate individual SD starters with output connected in parallel?, but the incoming MCCBs shall be mechanically and electrically inter-locked. Caution: the idle unit is LIVE
I will have to try as this is design requirement

A3. In marine application, the steering-gear system requires two separate starters and motors supplied from two separate sources; from different boards.
Noted on this

 

[che12345]

Dear Mr. Mark.H
1. Thank you for enlightening us that it is "...an actual project at work but never dealt with..."
2. No matter how it is being resolved, it is going to be rather complex. Caution: Be aware of " over-looked same blind corners !"
3. I am of the opinion that replacing the SD by soft-starter. The price difference is not very much.
3.1 With [Soft-starter-off-VSD] instead of [SD-off-VSD], the control circuitry would be very much less complicated. Both the outputs from [soft-starter and VSD] are three wires. The motor may be linked in star or delta formation; to suit the system voltage.
Che Kuan Yau (Singapore)

 

[LionelHutz]

If the project "must have" a wye-delta starter as bypass and the nature of the project means its much easier to do as asked vs trying to convert, then do as asked. I don't any reason to expect the controls to be much more complex compared to a soft-starter bypass.

 

[itsmoked]

I've also marveled that every soft starter I've looked at has cost the same or more than the same hp VFD. Maybe something about VFD competition being about 3x soft starter comp.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

In small HP sizes VFDs are really cheap. VFD's have their own special UL and CSA standards which allow crap that no other motor control can get away with, such as really small clearances. I'm sure standards in other locations are similar since VFDs are all built about the same for global use. VFD's are rather fragile, I always say it's not if one blows up, but when it blows up.

There are much cheaper soft-starters as the HP size goes up, but they are rather poorly made too. There are decent cheaper soft-starters as the HP goes up too, and they can operate 20 years without an issue. Sadly, the company I'm with is wanting to transition from decent soft-starters to the low end ones.

 

[itsmoked]

Gesh. Cheaper ones with Jraef's favorite two poled 3 phase units I bet.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Mark.H]

Thank you all, great allure of information. I will put everything together and do this magic.

My only concern about this project is spotting the blind corners. A small mistake and I will send to hell both AHU and Control Panel.

 

[che12345]

Dear Mr. Mark.H (Electrical)(OP)1 Nov 20 02:50
Q1. "...I will put everything together and do this magic. My only concern about this project is spotting the blind corners. A small mistake and I will send to hell both AHU and Control Panel..."
A1. I noticed that you had posted on 3rd Nov a question on " ... motor starter vs thermal overload relay..."
Based on the question asked, I presumed that you are in the early stage of your career.
A2. Now back to the question on " SD/OFF/VSD ...". This set up is very much complicated!. Don't jeopardize yourself being " ... send to hell both AHU and Control Panel..."
A3. You " probably?" would not be able to handle it without guidance from the "very experienced" person. No magic would help.
Che Kuan Yau (Singapore)