Contactors for 200HP Wye-Delta Motor Configuration

[Cammando_Cool]

I am currently working on a project that involves a wye-delta motor configuration. The contactors that have been provided are rated for 150HP on the delta side and 125HP on the wye side, but the motor that I am using is a 200HP motor with an FLA of 233A. I am wondering if this is an acceptable configuration or if there are any potential issues that I should be aware of.

I understand that horsepower and amperage ratings are important factors when selecting contactors, but I am not sure if one is more critical than the other in this specific configuration. Additionally, I am not familiar with wye-delta starters and my question may not make complete sense, but I would appreciate any help or guidance on this matter.

Thank you in advance for your expertise and insights!

 

[Jraef]

My opinion: If you do not understand a Wye Delta starter, forget using it and get yourself a Soft Starter.

 

[infinity]

This is a Wye start-Delta run starter?

 

[petersonra]

Wye Delta starting systems are designed to have lower inrush and lower starting currents then across the line starting. It is kind of the point of that type of starting system.

I see this arrangement on European designed and manufactured air compressors. For some reason they like this arrangement, and it works pretty good.

 

[Cammando_Cool]

My opinion: If you do not understand a Wye Delta starter, forget using it and get yourself a Soft Starter.

I would love to do that. Unfortunately, this is a vendor provided system and I can't change it.

 

[ptonsparky]

I would love to do that. Unfortunately, this is a vendor provided system and I can't change it.

Ask the vendor to provide pertinent details and answer questions. Startup should be part of his contract at that size.

 

[petersonra]

Ask the vendor to provide pertinent details and answer questions. Startup should be part of his contract at that size.

Someone is probably trying to save money by starting it up themselves.

 

[retirede]

Someone is probably trying to save money by starting it up themselves.

Not just starting it up, but rolling their own Y-D starter using some random contactors. What could go wrong?

 

[ptonsparky]

I did a Y-D starter once. One of the local metal working shops lost all info to a machine they moved from one building to another. Some one had just cut the wires. Fortunately a CH catalog had the exact wiring diagram I needed. Didn't even know such a think existed prior to it, and never saw another.

 

[don_resqcapt19]

I would want to see the contactors with a rating of at least 72% of the motor horsepower based on the conductor sizing rule for wye/delta starters in 430.122(C)

 

[Cammando_Cool]

Ask the vendor to provide pertinent details and answer questions. Startup should be part of his contract at that size.

Yeah, we had asked them but their response was that this has worked for other equipment in the past with no issue. Part of the issue is that they had an option to upgrade to a 200HP motor but it doesn't seem that the contactors upgraded with it.

Just to give a quick update, they're getting the contactor and motor from ABB so I reached out to ABB tech support and they mentioned that the contactor is not rated for the motor. What's interesting is that the amp rating for the contactors is 300A, so the amp rating is sufficient for this contactor and motor combination but the horsepower is not. So the horsepower is just as important to consider for a contractor. I'm still trying to think that through since amps can be derived with horsepower given a few other variables.

 

[infinity]

I would want to see the contactors with a rating of at least 72% of the motor horsepower based on the conductor sizing rule for wye/delta starters in 430.122(C)

Since you're connecting two contactors to the motor the current on each set of conductors will carry 58% of the FLC. {58*125%=72%} Could each contactor be rated for only 58% of the FLC or would a 25% increase in contactor rating be required?

 

[zbang]

How's that? The main contactor ("1M") will carry the full load when in delta, at least in my understanding of the connections.

 

[jim dungar]

So the horsepower is just as important to consider for a contractor. I'm still trying to think that through since amps can be derived with horsepower given a few other variables.

The horsepower rating includes the ability to make or break 6x the FLA of the motor for starting currents.

 

[Cammando_Cool]

How's that? The main contactor ("1M") will carry the full load when in delta, at least in my understanding of the connections.

This was my understanding too. So I'm confused by that comment. The 1M contact should be fully rated for the motor.

 

[Cammando_Cool]

The horsepower rating includes the ability to make or break 6x the FLA of the motor for starting currents.

Could you expand on that? I don't think I understand contactors well enough. Is it basically the power required to make the connection and break the connection? So if you undersize it, it may have issues starting and stopping?

 

[Jraef]

Since you're connecting two contactors to the motor the current on each set of conductors will carry 58% of the FLC. {58*125%=72%} Could each contactor be rated for only 58% of the FLC or would a 25% increase in contactor rating be required?

In a Y-D starter, the two main contactors are sized fir a minimum of 58% of the motor FLC, the Shorting contactor is sized at 33%. The OL relay is likewise set for 58% (unless it is ahead of the entire starter).

The HP ratings on the labels of the individual contactors become meaningless in this case. Whomever the OP spoke to at ABB and the vendor is clueless. This is why I hate dealing with Y-D starters. I used to build them from scratch, but 90% of the people who use them in the field do not fully understand them. I’ve seen more catastrophic mistakes made with Y-D starters than any other technology, right up to the point of motor destruction.

 

[don_resqcapt19]

Since you're connecting two contactors to the motor the current on each set of conductors will carry 58% of the FLC. {58*125%=72%} Could each contactor be rated for only 58% of the FLC or would a 25% increase in contactor rating be required?

The code requires the conductors to have the 25% adder, so without documentation, I would want the same for the contactors.

 

[don_resqcapt19]

How's that? The main contactor ("1M") will carry the full load when in delta, at least in my understanding of the connections.

Every one I have worked on had 3 contactors and in run, the load is split across two of the 3. The third one is used for the start and shorts out 3 conductors to put the windings into a wye connection.

 

[Jraef]

The code requires the conductors to have the 25% adder, so without documentation, I would want the same for the contactors.

Nah, it only applies to the conductors. Motor conductors ALWAYS need to be sized to 125%, so even if used Across-the-Line, the contactor size rating takes that into account.