Overload Relay Validation 1

[Sparky2003]

Hi all.
Happy New year to everyone.

I am in the process of changing overload relays on 15hp 3phase electric motor - reason is current relay is going end of life.

Electrically the spec on the replacement is identical, however I guess I should be performing some sort of validation/verification.

Can anyone suggest what type of testing I should do. The electric motor works in an application where it drives compressor and fans of refrigeration unit.

Look forward to advice.
Thanks,
Sparky

 

[huntercon]

What is the make/model of the relay(s)?

 

[bklauba]

I agree with huntercon, the make/model of the relays are needed. There has been a great deal of progress in motor protection technology, and often the costs are trivial, especially compared to the costs of motor rebuilds or replacements.

 

[busbar]

There are overload-relay test sets like

http://www.phenixtech.com/products/Circuit_Breaker/brochures/30105-HC1-HC2-PORTABLES.pdf

 

[Sparky2003]

The overload relays are Schneider relays:
P/N's LRD22LS and LRD3357.
There is an online electronic catalogue on website

http://www.schneider-electric.com/

Which gives data sheets.

 

[jbartos]

Suggestion:

http://www.squared.com

http://www.schneider-electric.com/

etc. require login id and password
Are those available to be able to access the online schneider catalog?

 

[jbartos]

Suggestion: Important aspects of the overload relays are their characteristic I-t curves. It may be prudent to revise the model in electrical power analysis software, if you use one.

 

[ScottyUK]

Hi Sparky2003,

We had some bad experiences with the new Telemecanique oveload relays from this range. The relay uses a pushbutton to reset following a trip, and I seem to recall it has a test button too. There is a facility for resetting automatically, which is not the default option. Numerous times, we found that the relay refused to reset following trip. This fault occurred many times on new or refurbished equipment. In the end we gave up with the product and installed a Siemens part which has performed admirably, albeit at slightly higher cost.

Our distributor, and the engineer at Siemens A&D, both said that for small motors, there is not any significant difference in the thermal characteristics of two similar motors of the same rating from 'reputable suppliers' (their words) if built to the standard IEC frame sizes. Therefore the protection relays are largely interchangeable, as their characteristics are designed match the thermal behaviour of a typical motor. When questioned further, we were advised to avoid using O/L relays designed for large motors turned down to the bottom of their range, as the time constant is optimised for the larger motor.

My personal opinion is that the newer (2000 onward) Telemecanique ranges have in general shaved a penny or two off the manufacturing cost, but that the build quality has nosedived. We had practical experience of one of their newly-released ESD pushbuttons failing, after the clip-on contact block fell off the actuator head when the ESD was operated. The drive remained running. Some of the large panel builders had been notified of this design defect, but it had not been communicated to the wider electrical community. As you might guess, their pushbutton range is explicitly excluded from all our future panel designs. We have a large installed base of older Telemecanique equipment, and the older products are pretty good for the price we paid. They aren't the very best, but they certainly aren't the most expensive either. Our problems arise when the old equipment wears out and we have to replace with the modern equivalent.


Hope this helps,

 

[bklauba]

Try looking at Sprecher & Shuh solid state O/L's. These can be separately mounted, come in ranges that are quite wide (not restricted by bimetallic limitations). These are being sold with Allen-Bradley and Cutler-Hammer/Eaton names on them also, which is respectable company. (S&S are the mfr's)

 

[jbartos]

Suggestion: Visit

http://ecatalog.squared.com/catalog/173/html/sections/16/17316019.html

For: LRD22
However, there is no LRD22LS