Motor Starter Problems 1

[vosstire]

I have a US Motor model N865 30hp three phase motor, 208/230/460 on 208 service. This motor drives a Webtrol pump which cycles about 100 times per hour and provides rinse water at about 600psi. The motor starter is a Moeller DIL4M115 (24V50/60HZ) part number 209758 and is rated at 40hp.

We have fused three starters through about 100 cycles. I had an independent electrical testing agency inspect and test all components to confirm proper installation. No problems were identified. We have check the incoming power from the power company and the service voltage is closely around 208. The power company has put a recorder on the 150KV transformer which supplies us to check the output. I am awaiting results. Our total requirements for the site are about 750 amps, with the 30hp motor being the largest. We have five 10hp blowers that also cycle about the same and miscellaneous 2-5 hp motors servicing other equipment. Still the starter fails.

I have an identical installation using a Benshaw NEMA rated starter (same motor, same service) and have had no problems for the past year.

Is there such a difference between a Moeller Starter (IEC) than a Benshaw (NEMA) starter???

 

[DickDV]

100 starts per hour even softstarted is severe duty. Benshaw builds heavy duty rated equipment and probably has the heatsink figured for high heat capacity.

Most softstarters generate heat only during start/stop cycles being bypassed during full voltage operation. Therefore, starts per hour translate directly into heat.

At that starting rate, you might want to check the motor rating. Motors also take a beating thermally when starting even when softstarted and the manufacturer should be able to tell you if you are ok at that starting rate.

 

[itsmoked]

Wow that is nasty service!! Could you use VFDs and just idle the motors down and back up instead of off and on. Everything would be happier. Otherwise you should step up the starter sizes.. A lot!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[bigbillnky]

vosstire

Goodafternoon. I would suggest upgrading the starter to a NEMA rated starter. I have had considerable problems with Moeller in the past, so much so I totally avoid them. In all fairness though, comparing IEC rated equipment to NEMA is a night and day difference. This will more than likely solve your problem. Good luck.

Bigbillnky,C.E.F.....(Chief Electrical Flunky)

 

[AFab]

I am surprised you even got 100 starts from any IEC rated contactor used under this condition.
The only way I would do an application of this nature is with a solid state type starter. It would have to be designed to dissipate the heat not only from the device being used but from the enclosure as well. Don't forget the duty cycle of the motor.

 

[dpc]

Applying IEC contactors requires a completely different approach than using traditional NEMA-rated contactors. NEMA-contactors come in one model - extra-heavy duty. IEC contactors are rated for duty cycle, expected operations and have a narrower range of application than NEMA contactors.

I agree with the others that it is not surprising that a NEMA-rated contactor has outlasted an IEC contactor with this duty cycle. If you read the test and performance requirements, you'll see why.

But it is possible to buy good quality IEC-rated contactors. You just have to specify the duty-cycle and level of quality that you want. With 100 starts per hour, the NEMA contactor will not last all that long either, unless you aggressively maintain and replace the contacts. The motor won't last too long either. If it is really starting 100 times per hour, you should probably re-think the control scheme/process arrangement. There must be a better way.

Experience with IEC contactors in the US has not been good because most applications are from package suppliers who buy the cheapest contactor they can find that has an adequate horsepower rating. That buys a very light-duty contactor in the IEC world.

 

[jraef]

vosstire,
You have been "duped" into a thinking that plagues the entire motor control industry, that being the "NEMA vs IEC" debate. Both of those contactors are actually IEC designs. Moeller makes their own, the Benshaw contactor is made by LG in Korea (recently renamed LS Industrial Systems if you are going to Google it) and just private labeled by Benshaw. It was NOT designed per NEMA standards, but the trick that Benshaw did was to use the NEMA duty cycle test standards and oversize the IEC contactors to suit their labeling of it as a NEMA sized contactor. You could have done exactly the same thing with the Moeller contactors, or any other brand name for that matter. Instead, someone selected the Moeller contactor based on lowest price out of the catalog without reading the application details.

The difference is in the duty cycle for the most part. NEMA makes no distinction for what is called "inching and plugging duty", which is essentially as high of a duty cycle as you can expect. IEC on the other hand specifically details the duty cycle that you can use and a process of selecting larger sizes for higher duty cycles. That Moeller contactor is rated AC-3 at that HP for instance, which if you read the catalog says the following:

AC-3 category may be used for occasional inching (jogging) or plugging for limited time periods, e.g. for setting up a machine. During such limited time periods, the number of such operations should not exceed five per minute or ten in any ten minute period.

100 starts per hour is roughly 17 starts in a 10 minute period, exceeding the limits of any AC-3 rating. You needed to go to the next size up at the very least.


The LG contactor with the same HP rating as the Moeller, the GMC-125, is actually rated for 150A instead of 160A for the Moeller. Benshaw however, sold you as their "NEMA" rated contactor, their relabeled LG #GMC-150, which is rated 210A. Had you selected the Benshaw unit without using their "NEMA" size on the chart, you would have also ended up with the lower rating. Had you selected the next size up of Moeller contactor, the DILM185, it would have been rated 225A and likely would survive in your application as well. It's all about reading the details.

I would NOT do that application with a solid state starter by the way, they cannot handle that duty cycle at all without prohibitively expensive derating. Most soft starters can handle 6 - 10 starts per hour.

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[waross]

I would strongly suggest finding a way to leave the motor running. It may even be cheaper energy wise and it will be much easier on both the motor and the starter. Consider a solenoid operated dump valve to return the rinse water to the supply tank when it is not needed.
Re IEC vs NEMA. Some starters have both IEC and NEMA ratings on the side. The same starter has a much lower NEMA rating than IEC rating.
respectfully

 

[ScottyUK]

vosstire,

Ther was some discussion on NEMA v's IEC contactors in thread237-152831. Moeller's equipment isn't so bad: they are just playing the same specmanship game as all their European competitors regarding (to my mind) over-stating the capability of their contactors. Judged among their peers, Moeller's products are on the whole fairly reasonable.

That starting duty will be tough on any contactor, not to mention the motor. This sounds an ideal application for a VFD, or maybe a recirc. valve to dump the pump output back to the reservoir when not required at the spray nozzle. The pump forum, forum407, might have some suggestions if you explain that from an electrical perspective it is better to leave the pump running.

Of course, the most economical solution may just be fit either a NEMA contactor or a much bigger IEC type. The contactor, in IEC pricing, would be about 60GBP for a decent brand. That doesn't buy many man-hours of design.


----------------------------------

I don't suffer from insanity. I enjoy it...

 

[itsmoked]

You may be able to use an accumulator that could allow you to skip motor cycles.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[AFab]

I had a similar application with a brake motor starting as many if not more times/hr as this. I used a 3 pole triac type module from carlo gavazzi. The motor also had to have an independent blower for cooling. The starter lasted for years.

 

[itsmoked]

AFab; 40hp??!?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[vosstire]

Thanks to all who repsonded to my inquiry, we replaced the Moeller starter with a Benshaw RSC 150-U-120 (NEMA rated @ 40hp) and everything seems to be working fine for the past week.

 

[aolalde]

Vosstire, Please keep us updated.

 

[GGOSS]

Haven't read all the above response (time shortage issue) so I appologise if I'm going over old ground here.

Are the Moeller contactors failing electrically or mechanically? Note that mechanical failure, can present itself as electrical failure if left un-noticed for some time.

Possible solutions:

Solid State Contactors - I have used these on applications involving up to 3 thousand (used the words instead of the numbers to save you checking) starts per hour albeit on non-motor driven loads. For many of those I worked with Payne Engineering products type 11C, in case you are not already aware Payne Engineering are US based. Don't know if they still make them and/or if they do them to 40hp but might be worth a call.

Soft Starters - I have soft starters on palletizing machines doing in excess of 300 starts per hour no problem. If you know thermal details for SCR's and heatsinks you can calculate/size a soft starter correctly. If not, at that duty cycle, you might select a soft starter to have an FLC rating approximating the LRC of the motor. Becomes expensive as indicated by jraef.

Variable Speed Drives - Good solution because the motor would not see anywhere near the same level of over-current during each start (compared to solid state contactor or soft starter)and therefore should last a heck of a lot longer.

Beyond those you can look to mechanical solutions like clutch/brake assemblies etc etc.

Hope that helps.

Regards,
GGOSS
PS: Stop bashing the IEC stuff, it works extremely well when selected correctly. BTW, selection based on AC4 duty sounds like it would be the go here, that is, if you want to persist with 'rattle and bang' technology.

 

[LionelHutz]

Jraef is basically correct about the contactors. However, the reason the Benshaw is surviving is not really for the reason he has given. A NEMA size 3 is rated for 25hp @ 208V and a NEMA size 4 is rated for 40hp @ 208V. So, to run a 30hp motor you end up with this NEMA size 4 contactor which is oversized. This is just because of the steps in the NEMA contactor ratings, not because of contactor rating manipulation.

Above the Benshaw RSC-50 or LG/LS GMC-50 contactor the IEC, UL and NEMA ratings are actually very close. IEC contactors are rated in current and NEMA contactors are rated in HP so you never have a direct comparism. But, using FLA x 125% comes out to having AC3 and NEMA matching fairly closely.

GOSS is correct. IEC isn't bad. Improperly picking IEC parts is bad. Picking the cheapest, lowest rated IEC component that still meets the current requirements just to get the lowest price without considering the application requirements is bad.

 

[jraef]

Sorry if it appeared as though I was besmiching IEC ratings, I was not. I was trying to point out that the reason the Benshaw lasted longer is because it was larger than the Moeller, not because it was NEMA vs IEC. As I said in the beginning, both of them are actually IEC design contactors. They just bought a larger one with the Benshaw brand name, as they should have from Moeller. Had they done so originally, it most likely would have lasted as well.

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