Fact or fiction: shutter motor with higher Nm then required wears down faster? - Page 1
Forum section: electronics / projects

author: Kjelt
author_rank: Super Contributor
timestamp: August 16, 2016, 09:42:58 am
content: Hi,the motor of my rolling shutter has about died on me (can not lift the shutter anymore after 30cm).So I requested the company that installed it 12 years ago to replace the motor with a new one, preferably higher power (more Nm) so it will last longer.The Nm's of the motor are matched with the weight of the shutters (as I understand it), so for instance a 10Nm motor can pull 40kg and a 20Nm can pull 80kg.So my gutfeeling tells me the heavier the motor, the easier it will have it pulling the weight, thus the longer the lifetime.To my suprise the guy told me that this was not correct. The contrary if the motor was too heavy for the shutter it would wear out faster and the lifetime would shorten.He would (if I insisted) gladly supply the more expensive motor but told me he would ask me to sign a disclaimerform so the warranty period would not be valid.So since I am not a motor expert and this guy has the practical experience and knowledge I rely on his advice.But I do not understand the principle, and am eager to learn why would a higer powered electromotor run out faster when the load is lower ?

author: Pjotr
author_rank: Frequent Contributor
timestamp: August 16, 2016, 10:21:53 am
content: Although all depends on the total design:More Nm --> operates faster --> higher friction --> more wear

author: wraper
author_rank: Unknown
timestamp: August 16, 2016, 10:33:35 am
content: If something will wear out faster, that's not a motor itself but what is driven by it.

author: DTJ
author_rank: Super Contributor
timestamp: August 16, 2016, 11:06:43 am
content: What is the drive mechanism. The increased torque could cause failure of gears / belts / levers or whatever.

author: mikerj
author_rank: Super Contributor
timestamp: August 16, 2016, 11:17:10 am
content: Quote from: Pjotr on August 16, 2016, 10:21:53 amMakes no sense,1) Why would the friction increase at higher speeds? Frictional loss may increase during the shorter period that the motor operates (assuming it turns faster) but the friction itself isn't likely to.2) You are assuming the motor capable of delivering a higher torque will turn faster, this may or may not be the case.Sounds to me like the original statement made to the OP was a load of rubbish, likely stemming from a lack of knowledge on behalf of the supplier. A higher torque rated motor/gearbox used under it's maximum rated load should not suffer a shorter life.

author: Kjelt
author_rank: Super Contributor
timestamp: August 16, 2016, 11:35:12 am
content: These are tubemotors and have a fixed rpm independent on the load.No belts, but they are restricted in time to operate due to (over)heating. AFAIK the overheating will be the main cause of wear although it has a resettable temperature protection.Example spec. see attachment.I am just as puzzled

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2016, 11:38:38 am
content: Quote from: DTJ on August 16, 2016, 11:06:43 amYep. After 12 years there's bound to be some joints in the door that are full of dirt, a bit bent, etc. Increased torque could start to break those.Not sure why the motor itself would be at extra risk though (assuming it turns at the same speed).

author: metrologist
author_rank: Super Contributor
timestamp: August 16, 2016, 11:44:52 am
content: Perhaps the higher powered motor that supplier has are just not as good. There is no direct correlation between motor power and motor life as far as I can tell, so there must be other factors.

author: Pjotr
author_rank: Frequent Contributor
timestamp: August 16, 2016, 12:01:30 pm
content: As suggested not necessary the motor wears out faster but the system or parts thereof. In general, driving a system harder than it is designed for can increase wear. Without knowing the details you can only guess why or conclude fact or fiction in this case. As OP noted, the supplier of the system had some experience.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 16, 2016, 12:09:09 pm
content: Too little information about the case, and too many generalizations and failures at trying to abstract the issue down to simple numbers like "motor torque" (what does that even mean in this context?). It's very hard to give any insight with this only this information; we would need to evaluate the complete system.Most probably (but just guessing), the "motor torque" number you are looking at is totally irrelevant, and the distributor is correlating something else that matters with it.

author: Fungus
author_rank: Super Contributor
timestamp: August 16, 2016, 12:43:05 pm
content: Quote from: Siwastaja on August 16, 2016, 12:09:09 pmIt may be down to personal experience. The dealer has seen a lot of higher torque motors fail.He doesn't really know why, they just do. It might be the brand, it might be the installation...who knows?ie. He's bullshitting you with the "why?", but not the "what?"

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 16, 2016, 04:48:02 pm
content: why the old motor failed? is it brushed? or not? if the brush wear out, you may not benefit longer lifetime with larger motor. since you mentioned more dirt hence more Nm requirement, that will put more electrical energy to the bigger motor, and hence of course shorter lifetime, regardless of motor rate. the last probable thing is that you asking for non mainstream setup hence there is no guarantee it will meet original design. whatever excuse you give, nobody is bloody care to pull 12 years old design drawing back for you.

author: vodka
author_rank: Frequent Contributor
timestamp: August 16, 2016, 05:43:34 pm
content: QuoteOne question , when the shutter halted to lift ,Does the motor stop or continue to move ?If the motor stop it , it might be that the limit switch had to get on bad posistion by blaming the axial movement from link shutter when it goes down or goes up.These movement cause us very breakdowns, since reset the limits switch(that the shutter stopped a determinate heigh or that it didn't stop) until cut the electrical wires.QuoteUsually, these motors are induction of the type squirrel cage

author: C
author_rank: Super Contributor
timestamp: August 16, 2016, 06:10:01 pm
content: See a lot of assuming that motor rotates at constant speed.Smaller motor will have less rotating mass and this allows faster speed changes. The less force slows the back to speed.The lower Nm leads to softer load pickup.

author: SeanB
author_rank: Super Contributor
timestamp: August 16, 2016, 06:49:57 pm
content: Seeing there is no mention of any battery backup ability, I would guess you have a system that uses either an induction motor, or more likely a high voltage universal or permanent magnet motor as drive source. Induction motor will only be very old systems, as the motor is large, so for an in roller system you will have a permanent magnet motor as drive.Most common failures on these drive systems ( used a lot on garage doors, gates, and sliding doors) come down to either the motors blowing up from overtemperature destroying the insulation ( they can be surprisingly well sealed as well, I had one which totally crisped the motor internally, and there was absolutely no smell of cremated insulation till the motor screws themselves were removed), the brushes wearing out, or more commonly the gearbox destroying itself, mostly from overload.They work best with a well balanced door to begin with, you first need to have the roler shutter balanced on the springs so the door itself can be opened and closed using only a single pinkie finger on the bottom edge. Then you need to keep the door slats dirt free, and the edges with the felting layer lubricated with a dry lubricant, and dust free. the door jamb must run true as well, and must not bind at any point.But then, I am not a fan of in door actuators, I did my one with a linear actuator running along the side, using a link to get drive to the door itself and stiff enough that there is no flexing of this link. had to invalidate the warranty as well, i had to turn the drive motor 90 degrees to get clearance, and I really should get a new track to get the last 20cm of travel, but it still is clearance for the car. Also added extra limit switches as the built in ones are not too accurate on the threaded copy track, so there are external limits with the on board ones as backup. just keep it lubricated and it gives no problems.Not going to get into the issues with the other door, which was a half ton of wood and steel, and with support springs that needed a clamping plate through the lintel to keep them from tearing out, and the difficulty of lifting this door after one grenaded. That used an induction motor, around a half horsepower, and a reduction box that drove a half inch chain running a carrier along a guide track. If the power was out, and the door was balanced properly, you could open it one handed after using the release.

author: vodka
author_rank: Frequent Contributor
timestamp: August 16, 2016, 07:40:47 pm
content: QuoteIf the voltage is constant,the load too is constant ,at consequence the velocity will be constant. A less that you refer at the moment to start until that the motor arrived to permanent regimem where the motor velocity changes. But this is to be few peevish.

author: C
author_rank: Super Contributor
timestamp: August 16, 2016, 08:30:48 pm
content: The load is not constant. You have load stopping and starting.What does the extra torque do at the limits?What does the extra torque do when something fails?Lower torque slows or stops, Higher torque rips it apart or adds extra stress.Stress over time does break things.The extra torque can change "repair the unit" to "replace the unit".

author: vodka
author_rank: Frequent Contributor
timestamp: August 17, 2016, 05:49:05 am
content: QuoteBut the load is the same because the shutter weight the same if it goes up as goes down.i think that you are confusing with the load(not vary) with torque (if vary) As you said when the motor starts to work the torque varies (not the load) until that it arrived to permanent regimem.During the temporal response from motor ,the constants parameters are voltage(always that electrical grid is clear) and the load while it varies are the current and the motor velocity.QuoteBesides, that the motor is sucking a huge current then the winds motor will die soonQuoteToday the great majority goods can't fix, you always have to replace.

author: Kjelt
author_rank: Super Contributor
timestamp: August 17, 2016, 07:13:32 am
content: Quote from: vodka on August 16, 2016, 05:43:34 pmThe motor tries to lift the shutter further, makes a noise that sounds like it is not able to and then stops.If I help the motor by manually lifting the shutter a bit it comes further but halfway still stops (without noise), extra help does not work anymore.The last months that was how I could open the shutter totally by helping it manually.So yeah you might be right that the last stop is now a moved limit switch, still not a good sign.But what I read on the net , 10 years is already a long lifetime, I think this one is over 12 years old so I am going to replace it just in case, these Somfy motors are pretty expensive over €280 a piece.Maybe I will take the thing apart and see if I can find the culprit.PS: this reminds me the Altus and Oximo motors do not have manually adjustable limit switches, they are all remotely controlled and configurable. Hmmmm the more I think about it the more I am thinking about taking it down myself and see what is going on.

author: vodka
author_rank: Frequent Contributor
timestamp: August 17, 2016, 04:50:23 pm
content: QuoteIt seems that the shutter roller gearbox have a broken teeth or worn teeth and when you help to lift for casuality move the transmission , it engages with a good teeth and begining to move ,but after of the one turn ,the motor returns to stop.Solution for the great public buy a new shuttler roller , for freaks,rats and bunglers remake the broken tooth or a make new gear with a lathe .

author: Kjelt
author_rank: Super Contributor
timestamp: August 17, 2016, 05:41:29 pm
content: That gearbox is the green white turning parts that are visible inside the motor ?If it was broken I would expect it to stop at the start when the load is maximum ?

author: Kjelt
author_rank: Super Contributor
timestamp: August 17, 2016, 05:49:03 pm
content: What would happen if the MKP motor capacitor is broken? I see a lot of repair videos for the somfy motors (not rts but still) where they exchange the capacitor like here (in german and french):

author: vodka
author_rank: Frequent Contributor
timestamp: August 17, 2016, 07:17:04 pm
content: QuoteThe capacitor is used for starting the motor , and when the capacitor is bad or fail , the motor usually doesn't work or it cost to begin to move, but it would be strange case that after travelling 30 cm ,it stopped.You could test the shutter on empty(without charge) for seeing that behavoir has the motor.QuoteYes, these are (three groups planetaries ).QuoteYes, it could pass

author: Kjelt
author_rank: Super Contributor
timestamp: August 17, 2016, 08:29:52 pm
content: I just tried to remove the shutterbox but there is a big problem, after the shutters were installed the patio was tiled with nature stones in cement.You guess it the styles of the shutters are in at least 5cm concrete/cement and the box is under the roof so no way to lift it verticallyThis weekend will start to figure out how to saw the styles off at the floorlevel or break the cement.On a positive note, I took off the mains from the shutter and after i put it back on I could again lift the shutter to the upperend.So it is now fully open and I will leave it at that for now till I figure out how to remove the darn thing. Now I am still unsure what is wrong with the motor but I guess it needs to be replaced anyway.Thanks for all the help and advice , appreciate it

author: Kleinstein
author_rank: Super Contributor
timestamp: August 18, 2016, 07:26:59 pm
content: If the motor stopped at 30 cm, chances are that it was just a mechnical problem with the shutter (e.g. drit in the rails). So the motor might be still Ok. I would first try to clean the rails and check for something bend.