# Delta Three Phase Motor Problem



## rekelly1989 (Jan 27, 2013)

I have a delta three phase 480 motor problem. The motor that I install keeps shorting out form phase to phase. Ratings on motor: .9 amp, 480, 1800 rpm, delta three phase. It is protected with a 1.1 amp overload. All three phases have correct voltage. Amp draw on each leg is: .823, .798, .803 average. start up spike is 1.9 amps on each leg. relay that pulls the motor in is good. What could be the possible problem?


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## ponyboy (Nov 18, 2012)

A phase to phase short? Are you sure that's what you got? Is the overload tripping or the circuit breaker or fuse? Did you Meg the motor and its feeders?


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## micromind (Aug 11, 2007)

What HP? Is it a NEMA frame or IEC?

A 0.9 amp motor should be drawing 4 or 5 amps while starting. A peak of 1.9 amps suggests a problem somewhere. 

As noted, the first thing I do with any motor that's causing trouble is megger it and its feeder.


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## l0sts0ul (May 7, 2011)

My guess is a 1 hp motor. If its drawing that current on each phase I don't see a problem. Do you have 480v phase to phase oneach leg?? What's the exct problem?


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## ponyboy (Nov 18, 2012)

micromind said:


> What HP? Is it a NEMA frame or IEC?
> 
> A 0.9 amp motor should be drawing 4 or 5 amps while starting. A peak of 1.9 amps suggests a problem somewhere.
> 
> As noted, the first thing I do with any motor that's causing trouble is megger it and its feeder.


My guess is his meter isn't catching the actual starting current.


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## l0sts0ul (May 7, 2011)

Also if he service factor is 1.25 or higher, based on the info you gave us, if the overload is tripping u could turn t up to 1.13-1.15. 


But with the current draw you have, it should be fine.


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## Big John (May 23, 2010)

ponyboy said:


> My guess is his meter isn't catching the actual starting current.


 Ditto.

OP, what are you seeing that makes you believe there's a problem?


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## ponyboy (Nov 18, 2012)

Big John said:


> Ditto.
> 
> OP, what are you seeing that makes you believe there's a problem?


I think he said hes got a phase to phase fault...wtf, that's like the wires slapping you in the face and telling you what the problem is


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## rekelly1989 (Jan 27, 2013)

*delta motor*

The motor runs a brush motor on a print unit so the load is low. I have replaced wire running from motor to overload (new) and relay (new) to the 8 amp breaker. I don’t know what’s wrong but they have been going through a lot of motors over the year, recently about one every two weeks.


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## rekelly1989 (Jan 27, 2013)

brush roller


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## Peewee0413 (Oct 18, 2012)

What all is in the circuit.


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## micromind (Aug 11, 2007)

Is it possible that something in the paint is attacking the insulation in the motors windings?


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## l0sts0ul (May 7, 2011)

I don't want to sound cynical, but I Think you're missing something here. All the stats you have given us indicate nothing is wrong with the motor. How do you measure the pase to phase short on the motor?

What is the impedance on each winding to each... ie a-b, b-c, c-a... and is the motor running in the right direction?


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## vileislepore (Jan 25, 2013)

rekelly1989 said:


> I have a delta three phase 480 motor problem. The motor that I install keeps shorting out form phase to phase.


its shorting out phase to phase? It seems like theres some info youre leaving out. What readings/symptoms make you think its shorting?


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## John Valdes (May 17, 2007)

The currents listed are way to low. This motor could very well be connected wrong.
Wrong like maybe its connected in a wye and should be connected for delta? This mistake will produce 1/2 the HP and little current.
Is the motor a 6 lead motor?


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## l0sts0ul (May 7, 2011)

^^^^ I would agree this is a logical point as well... but there has been no response from this gentleman


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## JRaef (Mar 23, 2009)

John Valdes said:


> The currents listed are way to low. ...


He said the motor is rated 0.9A, it is drawing ".823, .798, .803 average." I don't consider that way too low and only about a 3% current imbalance, most likely the result of a very slight voltage imbalance. If there numbers are accurate, I don't see a problem in them. The OP never said what the HP rating is, that was l0sts0ul's speculation. I think it more likely to be about 1/2HP, but maybe not really even that, see my response to him below.


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## l0sts0ul (May 7, 2011)

sorry, but with the little info I have, I had to make a calc and some assumptions.


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## JRaef (Mar 23, 2009)

rekelly1989 said:


> I have a delta three phase 480 motor problem. The motor that I install keeps shorting out form phase to phase. Ratings on motor: .9 amp, 480, 1800 rpm, delta three phase. It is protected with a 1.1 amp overload. All three phases have correct voltage. Amp draw on each leg is: .823, .798, .803 average. start up spike is 1.9 amps on each leg. relay that pulls the motor in is good. What could be the possible problem?


rekelly,
As others have said, it's difficult to do more than guess when we are not there, but here is mine.

Most printing machinery comes from Germany or Italy now, so the chances are high that this is an IEC motor, not a NEMA design normally used in this country. That motor will be rated in kW on the nameplate instead of HP, most likely a .37kW motor. In reality, that would actually be a motor rated for 400V 50Hz but will work at 460V at 60Hz just fine as long as the machine can live with the higher speed because of the frequency difference.

The problem with IEC motors is that they have *NO SERVICE FACTOR AT ALL.* In the IEC world, they do not believe in that concept, the motors are made as close to the bone as possible. What that means then is that when they say that the motor FLA is 0.9A, *YOU MUST SET THE OVERLOAD AT 0.9A.* I know when people read the NEC they see that part about protecting the motor at 125% of the nameplate rating, but that is a mistake in 99.9% of the cases. One reason is, that applies to NEMA motor designs. The other reason it is usually a mistake is because in many cases *THE OVERLOAD RELAY ALREADY HAS THAT 125% FACTORED IN*! So when you set the OL for the FLA, the point at which is begins to trip is going to START at 125% of that value. If you already set it for 125%, then the pickup point is 125% of 125%! That's now 156% and the motor suffers for it. This information is always described in the OL relay instructions, but for some reason most people don't read them.

Right now you say your Overload Relay is set for 1.1A. and although .2A doesn't sound like much, for this motor that is a 20% overload and on a motor NOT designed for ANY overload capability. That will mean premature insulation failure (if the motor runs into overload).

Most likely when you are observing the current everything is fine, but a some points in the operating cycle something puts that motor into an overload condition. It could be something as simple as the viscosity of the ink being different from what it was designed for, it could be a failing bearing somewhere, extra friction on the brush travel, any number of things.


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## vileislepore (Jan 25, 2013)

I don't understand why european engineers have to engineer their equipment so close to perfect conditions. we do not live in a perfect world.


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## John Valdes (May 17, 2007)

Sorry. I thought he said 9 amps.


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## Peewee0413 (Oct 18, 2012)

I don't even know why this is still being talked about. The guy hardly knows what the problem is. He can't answer any questions.


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## l0sts0ul (May 7, 2011)

I'm talking about it because I'm trying to up my post count by trolling a little


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## Wirenuting (Sep 12, 2010)

l0sts0ul said:


> I'm talking about it because I'm trying to up my post count by trolling a little


Now that's not nice to do.


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## Wirenuting (Sep 12, 2010)

l0sts0ul said:


> I'm talking about it because I'm trying to up my post count by trolling a little


Using another's thread just to up your count.


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## Wirenuting (Sep 12, 2010)

l0sts0ul said:


> I'm talking about it because I'm trying to up my post count by trolling a little


Seems kinda sneaky.


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## l0sts0ul (May 7, 2011)

I apologize .


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## chicken steve (Mar 22, 2011)

<oops>
~CS~


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## l0sts0ul (May 7, 2011)

Oops?? Is that even enough characters to count as a post?


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## JRaef (Mar 23, 2009)

vileislepore said:


> I don't understand why european engineers have to engineer their equipment so close to perfect conditions. we do not live in a perfect world.


Having worked for several IEC companies (Klockner Moeller, ABB, Siemens) over the years, I have put together a working theory based on my experiences with them;

After WWII in Germany, France and England to a certain extent, most "regular guys" were dead or crippled, but a lot of engineers survived because they had been needed in the war factories instead of the front lines. Guys with engineering degrees were a dime a dozen after the war then and had to work cheap, but tradesmen like electricians were rare and were needed for the harder work, or the engineers had to actually do the work. So that created what I call a "culture of engineers", where they had to constantly struggle to justify their existence. Being the fart smellers that they were, they quickly learned to spend as much time as they could engineering things to death so that they did NOT have to work on them. But materials were in short supply, so rather than over design with materials (because the companies told them they couldn't afford it), they made everything just barely adequate, but also so complicated that it was virtually impossible to repair anyway. The end result was that everything became throw-away because it was cheaper to replace it than repair it. The Germans I worked for were always referring to it as "rationalizing" a design. Whenever I had to design something, I had to be prepared to explain in excruciating detail exactly why I chose each and every component, as well as DOCUMENT it for posterity! It was a royal PITA and every project took 3 times longer than necessary.

Here in the US, "Engineer" was a capitalized word and usually only the elite got to go to engineering school, so they were in short supply and expensive. But tradesmen like electricians were cheaper and plentiful, plus there was no shortage of materials. So companies here used their expensive Engineers to over design everything but keep it simple by using wide ranging standards with built-in fudge factors so that electricians could pick out the right product without talking to an Engineer. That way if it so happened to be a nasty application you were covered, but if not, well, who cares, it will work forever. That's how we ended up with things like NEMA designs for motor starters and AC motors with 'Service Factors'. So US manufacturers were saying "Who cares if the motor needs 8HP to do the job, throw on a 10HP motor that in reality is a 12HP motor and don't think about it any longer. Then have the electrician use a NEMA size 1 motor starter that is capable of plug-reversing it at full speed and operating at 70% voltage, even though it's never going to be that bad. What the hell, they're cheap at twice the price compared to my ivory tower Engineer spending 3 hours 'rationalizing' the damed thing. Get 'er done!"

When I first worked for Klockner Moeller, the idea of replacement contacts for a contactor was a totally foreign concept to them. When we in the US would complain to HQ in Germany that our customers demanded it, they would respond (in a thick German accent) "Vat for zey need zat? Eet is schtupid to replacen der contactens, yah? You tell zem zey need to buy new contactor yah? Don't be dumpkoff..."

Seriously, I had almost that EXACT conversation once.


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## sparkywannabee (Jan 29, 2013)

Have changed about 30 water brush motors on different presses(Goss/Harris) last few years, nasty, dirty cramped area, ink, oil, paper dust all over, brush motors are 3 ph, no drive or feedback/speed control since brushes turn at constant speed, like oil pump motors, unlike about everything else on a printing press. Important to check amp draw after been running for awhile, sometimes bearings get tight when they get hot, belt should not be too tight, make sure etch isn't running down the liquidtight into the peckerhead from a leaky Jbox, if you are using 480V make sure motor is wired up for it.


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## vileislepore (Jan 25, 2013)

JRaef said:


> Having worked for several IEC companies (Klockner Moeller, ABB, Siemens) over the years, I have put together a working theory based on my experiences with them;
> 
> After WWII in Germany, France and England to a certain extent, most "regular guys" were dead or crippled, but a lot of engineers survived because they had been needed in the war factories instead of the front lines. Guys with engineering degrees were a dime a dozen after the war then and had to work cheap, but tradesmen like electricians were rare and were needed for the harder work, or the engineers had to actually do the work. So that created what I call a "culture of engineers", where they had to constantly struggle to justify their existence. Being the fart smellers that they were, they quickly learned to spend as much time as they could engineering things to death so that they did NOT have to work on them. But materials were in short supply, so rather than over design with materials (because the companies told them they couldn't afford it), they made everything just barely adequate, but also so complicated that it was virtually impossible to repair anyway. The end result was that everything became throw-away because it was cheaper to replace it than repair it. The Germans I worked for were always referring to it as "rationalizing" a design. Whenever I had to design something, I had to be prepared to explain in excruciating detail exactly why I chose each and every component, as well as DOCUMENT it for posterity! It was a royal PITA and every project took 3 times longer than necessary.
> 
> ...


thats the best explanation I've ever heard! in all actuality, it makes a lot of sense. I deal with an Austrian machine manufacturer (EVG) quite often, and basically they've engineered their machines to the point that their technicians probably should buy property here in the States and move here permanently. Also, I'm very jealous of their work schedules/vacation time. Those guys definately have the right idea as far their priorities. But it makes working with them almost impossible. I can only call their tech support from 2am until 8am and most of that time they are in "meetings" or taking ridiculously long lunch breaks. The last time I called them, it was their last day of work before the holidays, in which they were on holiday break from Dec. 21st to Jan. 7th. What is this? elementary school?


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