Full Voltage non Reverse 2300v induction Motor Starter

[BearB]

Where I am working they want to rebuild a Full Voltage non Reverse 2300v induction Motor Starter. I have not worked much with medium voltage starters and I am asking for assistance. We have several older 2300v Induction motor starters that have had the motors and equipment removed. I am going to use the control circuit and size components to the motor being installed. The control circuit is: 2 overloads controlled by 2 CT's and a GCT controlling a relay. Along with a start and stop switch that controls a 230vac relay and a contact from that entergises the main contactor. The current components are too old or undersized so they need sized to the motor being installed. The induction motor being installed is 450 hp, 2300v, 111 amps.
I was considering using 2 150/5 CT's, a Cutler-Hammer Vac. 400amp Contactor (because this device is available in our company store room. The 2300/230 transformer is in good shape and will be used. I need assistance sizing components. Are the CT's proper size?, What type of overload relays ? What type of ground fault CT and relay? contactor ok? Any assistance is appreciated.

 

[Laplacian]

First, what is the original starter cubicle? Is the C-H contactor compatible with this cubicle? Does your C-H contactor have a 230VAC coil? Are your feeder cables sized correctly?

The CT ratio is fine. For ground fault protection, we have good success with the GE (ITI) ground fault detector or the A-B detector. Both are sold as a set with the relay module and the sensor (looks like a CT). Note that the GF relay can only be used to trip the contactor if you have a resistance grounded system that will limit ground fault current below the contactor's interrupting rating.

Do you need a new overload relay, or just the heaters? You need to size the heaters for 3.7 to 4.3A depending on the motor's service factor, condition and availability requirements. You also need to install adequate R rated fuses (9R for example) for short circuit protection.

This is not meant to be a substitute for real professional guidance.

 

[BearB]

Westinghouse was the original starter cubicle.
1 0 cable is the size it will be in a cable tray about 100' run.
The C-H contactor coil is 230vac.
Thge C-H contactor will fit in this cubicle. It had an Ampgard contacor in it which was much larger than the C-H Vac. contactor.
I need 2 new overload relays to work with the CT's.
Any more suggestions with this information. What type of overloads?
Thanks for you sugggestion. It is appreciated.

 

[oldfieldguy]

One point to consider:

Did the original starter have a mechanical connection to the door latching mechanism to prevent the cubicle door from being opened when the contactor was connected to the 2300 volt source? This is the case with newer equipment, but is not necessarily so in much older equipment.

I think it was the case with Ampgard.

If so, you will ahve a bit of a task getting the C-H contactor to interface with the mechanism, and failure to do so properly will disable some important safety interlocks. The circuit will work, but you will have defeated some important safety devices. This is a BIG problem form a safety standpoint and is one of the bigger hurdles to jump in trying to retrofit older air-break equipment with new vacuum contactors.

old field guy

 

[jraef]

Having only 2 overload devices was made illegal (from a Code standpoint in the US) some 30 years ago. I would suggest that this is a good time to update your overload to a full motor protection relay, preferably one that also accepts a GFCT so that it can integrate the ground fault protection into the same device. My favorites are the Siemens SIPROTEC, GE SR469, Eaton MP3000 or Schweitzer SEL Series. Clean it up, make it safe and reliable.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[BearB]

Thanks guys for all your input this is a great web site for assistance.
Does anyone have information on a Ground Fault CT with associated ground fault relay for this application.
I agree Jraef a programmable Protection Relay would be best but in another area of the plant there is a Multilin installed on a starter and the repair person blame that unit whenever the device faults and this package has been installed for years. I cannot fight that at my level. I just want to update a circuit with new components that the repair persons understand.

 

[jraef]

This is the simplest system out there.

http://www.geindustrial.com/products/specs/GFM.pdf

But it's still not a good idea to remain with only 2 OL sensors. If your budget is tight, at least put something like one of these on as your OL relay. Since it also does GF protection (residual current method only), maybe you can call it the GFR and indirectly end up with a better OL as a side benefit. If you have a resistance grounded system however, you will still need the Zero Sequence GRF as shown above.

http://www.symcominc.com/catalog/motor_protection/777-MV.html

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[oldfieldguy]

BearB-

The Multilin 236, 269 and 369 are what I termed "technician's relays. They are simple enough that a knowledgeable technician can install one and do a very capable job of upgrading his motor protection without a lot of engineering support.

I do recommend the third CT for phase protection, and they also sell a ground fault CT suitable for use with their product. Installation and setup are simple for somebody with a normal amount of knowledge of motor protection and control. And if you're replacing a set of thermal overload blocks, the Multilin curve 3 or 4 will give you generally the same time-overcurrent characteristics.

old field guy

 

[BearB]

Thanks

 

[swn1]

The selection of the GFCT depends on how your system is grounded. You need to know minimum and maximum GF currents.

I second the recommendation for a Multilin 239.

 

[Laplacian]

I'm going against the popular recommendation of the Multilin even though "technically" it's the superior choice.

His site has a single Multilin with bad experience. I can echo the poor reliability issue, especially units installed in outdoor motor starters. Displays, power supplies and capacitors have been constant sources of failure at our site.

Even though Multilins are user friendly, his maintenance people don't understand them. If they had a high population in plant to support, this would not be an issue. Training is not the easiest thing to get across to unmotivated, "short time" attitude maintenace technicians.

The OP did not state application, but if it's process critical, you want the minimum protection required on the motor to minimize nuissance shutdowns. Multilins installed outdoors have false tripped our facility so many times that thier trip contacts are jumped out on all critical units.

The OP still needs to provide maximum ground fault current, application, reliability requirements, and availability targets to make the best recommendations. The best protection for the motor does not provide the best availability for the process.

Condition monitoring is important also, but that is a different maintenance issue.