# Can I trust household appliances with integral VFD?



## Electric_Light (Apr 6, 2010)

When everything was electro-mechanical, there wasn't much to go wrong beyond visible wear and tear and I despised extended warranties. When electronics first came into play, they were only for driving user alerts and relays (for example, logic level board on microwave that drives the buzzer and relay). 

I just got a front loader "he" washer and to my surprise, the drum is operated with a delta-wound shaft tach three phase motor. The motor itself is piggybacked on sprung system. It is driven with a three phase output VFD with tach input and all aspects of operation is controlled by PLC built into washer main board and the two talks to each other by serial bus. 

Extended warranty is like $200. VFD is like $250. 

I suppose household 120v AC is cleaner than 480v with a bunch of inductive loads cycling on and off, but can I trust it to be reliable as old school core and iron technology? 

It's a washer, so if the motor can't fire up, then its a trip to laundromat and the worst that can happen is a dead short tripping the washer branch circuit, but if this was a freezer with $1,000 of food inside, I would feel really uncomfortable if VFD failure would render the motor inoperable.


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## Introyble (Jul 10, 2010)

I sold my front loader. Luckily I had purchased the extended warranty ~ which was a major help when reselling.

What your calling the PLC is more like a micro logix controller. Mine was all proprietary OEM type crap that you couldn't repair yourself.

I had a service man out 3 times, each time it was like a mother board (or plc cpu) failure.

I finally sold it with 4 of the 5 years remaining on the extended warranty.


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## Electric_Light (Apr 6, 2010)

Introyble said:


> I sold my front loader. Luckily I had purchased the extended warranty ~ which was a major help when reselling.
> 
> What your calling the PLC is more like a micro logix controller. Mine was all proprietary OEM type crap that you couldn't repair yourself.
> 
> ...


The VFD unit, which they call "MCU" is replaceable separately, but the controller is built into the motherboard and the program is on the onboard EEPROM. 

It's not just "he" washers that are using VSDs though. Many HVAC air handlers for residential furnaces are using BLDC motors with integral or external proprietary motor drive while 3-phase input multi-hp commercial air handlers use external VSD unit.


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## Jlarson (Jun 28, 2009)

In my experience a lot of the board level stuff like that is crap.


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## Vintage Sounds (Oct 23, 2009)

Many higher end mini-split air conditioners sold in hot 240v countries now use VFDs to drive their compressors. They're marketed as "DC Inverter" but the inverter is obviously only a part of the picture. It makes sense where the electricity cost is high enough that the savings could offset the initial investment.


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## MDShunk (Jan 7, 2007)

I think the technology has matured sufficiently that this shouldn't be a huge concern. Many of the better garage door openers have had DC drives in them for some time, and the it's a natural progression to go to VFD's in water saving clothes washing machines.


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## etb (Sep 8, 2010)

Jlarson said:


> In my experience a lot of the board level stuff like that is crap.





MDShunk said:


> I think the technology has matured sufficiently that this shouldn't be a huge concern. ...


In dabbling in appliance repair over the years I find both views to be correct. It _shouldn't_ be a problem: some boards are crap, others are top notch;hard to tell what you're buying when in the store. As VS mentioned, it's becoming common in the near eastern A/C market, but they're also hot in Japan where energy costs are high.


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## guest (Feb 21, 2009)

Is it more reliable? Depends heavily on the brands you buy. Samsung and LG are essentially the same, high quality and both made in Korea. The lower-end front loaders tend to not be as well made and I wouldn't trust them at all. 

And since there is a lot going on with the direct drive drum (weight sensing as current vs. speed, reversing, variable ramp times, etc.) you could not simply replace the controller with a VFD. 

Biggest problems with HE machines so far seem to have been with the drain pumps, door locks and control buttons sticking/failing. 

I would put any of these machines on a quality brand surge protector to be on the safe side.


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## Electric_Light (Apr 6, 2010)

How does the tachometer signal on a three phase motor like this one? It has two leads. Does it make contact x times a turn, does it create frequency output or what does it generate that the VSD use to monitor it? 




mxslick said:


> And since there is a lot going on with the direct drive drum (weight sensing as current vs. speed, reversing, variable ramp times, etc.) you could not simply replace the controller with a VFD.


The direct drive probably uses electronically commutated DC motor and its not driven the same way. The newer direct drive like the LG is most likely an outrunner permanent magnet BLDC. While they both have three leads, they're not driven the same.


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## miller_elex (Jan 25, 2008)

The problem with drives is fluting on the motor shaft bearing race from unwanted currents.

This problem increases with an increase in carrier frequency.

So more than likely, if there is problems, mechanically it will be a bearing problem, and electrically, it will be a problem of power quality due to the large linear load caused by the rectifier assembly.

I think they've got solutions for the bearing issue, but when it comes to power supplies, every manufacturer is going to cut corners when it comes to power quality going back out the line side.


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## Bob Badger (Apr 19, 2009)

I was involved with repairing fluted bearings on four 500 HP motors. When some testing was done we had about 17 amps of unwanted current. 

The bearing solution was to install ceramic coated bearings, the GE techs that did this said that was only going to fix the issue in the motor bearings and move the problem into the bearings on the driven load.

The main cause was the fact we installed the load side of the VFDs exactly like the engineers had specified which was exactly opposite what the drive manufacturer recommended. (THHN Line and load of four 500 HP VFDs in a common cable tray)


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## Bob Badger (Apr 19, 2009)

These may not qualify as household appliances. :jester:


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## Jlarson (Jun 28, 2009)

Bob Badger said:


> These may not qualify as household appliances.


I don't know, it kinda looks like what I have running my dryer.


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## jza (Oct 31, 2009)

Bob Badger said:


> These may not qualify as household appliances. :jester:


How many horse?


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## etb (Sep 8, 2010)

Bob Badger said:


> The bearing solution was to install ceramic coated bearings, the GE techs that did this said that was only going to fix the issue in the motor bearings and move the problem into the bearings on the driven load.


Where shaft grounding brushes/rings not an option?



Bob Badger said:


> The main cause was the fact we installed the load side of the VFDs exactly like the engineers had specified which was exactly opposite what the drive manufacturer recommended. (THHN Line and load of four 500 HP VFDs in a common cable tray)


May I ask why they concluded that this was the problem? Certainly mfrs advise against it and it is plain ole dumb for an engineer to spec that. But I've never heard of and can't understand how that would cause shaft currents. Usually the problem is noise fed back to the line side; sometimes going upstream, sometimes affecting the drive itself.


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## frenchelectrican (Mar 15, 2007)

jza said:


> How many horse?


 
According to the common fans and I kinda figure out with conductor size and I am leaning toward between 350- 400 HP.

Merci.
Marc


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## Bob Badger (Apr 19, 2009)

etb said:


> Where shaft grounding brushes/rings not an option?


There where added, but as we all know electrons do not just take the path we want them to, they go all paths so while grounding brushes may divert some of the current it will not stop the current from taking other paths. At the job I was at the remaining path would be through the bearings supporting the large fan. 




> May I ask why they concluded that this was the problem?


About a week of testing with me and my crew making different types of changes while groups of engineers with a ton of testing equipment noted what the changes did to the currents.

They provided us a metal mesh 'sock' that we had to slide over the input and output conductors essentially making a 3-conductor 600 Kcmil VFD cable

After the testing and finger pointing they replaced all the cable tray with RMC.

I have not been back to the sight since the testing so I can't tell you if this change to RMC fixed the problem.


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## Bob Badger (Apr 19, 2009)

frenchelectrican said:


> According to the common fans and I kinda figure out with conductor size and I am leaning toward between 350- 400 HP.


Close, 500HP.


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## miller_elex (Jan 25, 2008)

Bob Badger said:


> There where added, but as we all know electrons do not just take the path we want them to, they go all paths so while grounding brushes may divert some of the current it will not stop the current from taking other paths. At the job I was at the remaining path would be through the bearings supporting the large fan.
> 
> After the testing and finger pointing they replaced all the cable tray with RMC.


Yeah, I worked for an outfit that reps the ABB's in their service dept. They were a really great shop that ran out of work.. 

But, we always seperate the drive inputs and outputs. The output is really like a radio frequency transmission line, it bleeds all kinds of EMI and harmonics onto adjacent objects, which need to be well bonded. 

Another way to reduce the unwanted currents in the rotor is to lower the carrier frequency, but I'm sure you guys had it as low as possible for that 500hp.



A coil charges in five time constants. What the pulse in the PWM waveform does, is charge the the stator winding (a coil,) to the voltage point where it would be on an equivalent sine wave. 

Ahhhhhh, time to consult Carrow's Guide to VFD's, one of the finest books EVAR!!!! Muah ha ha hahaaa


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## wwilson174 (Apr 25, 2008)

I can't help wondering what goes through the minds of the ropers when they read a thread like this!


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## miller_elex (Jan 25, 2008)

wwilson174 said:


> I can't help wondering what goes through the minds of the ropers when they read a thread like this!


'Umm.. G.D. thats garbage disposal there.... D.W. thats the dishwasher homer.... I wonder if there's a drive on that?? Should that be a 12/2 now??'


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## Bob Badger (Apr 19, 2009)

Here is the control for the fans and related scrubers.




















Outside ....


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## HARRY304E (Sep 15, 2010)

Bob Badger said:


> These may not qualify as household appliances. :jester:


 Thats my oil burner motor :laughing::laughing:


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## etb (Sep 8, 2010)

Bob Badger said:


> There where added, but as we all know electrons do not just take the path we want them to, they go all paths so while grounding brushes may divert some of the current it will not stop the current from taking other paths. At the job I was at the remaining path would be through the bearings supporting the large fan.


Ah. On all of the smaller drives we put those on, that happened but the current through the load bearings wasn't enough to worry about. I've never worked on a drive that large. We did have a had 40 hp or so with the problem you described. Luckily for us there was a stock size ring that we were able to use on the load as well. We bonded the frames of the rings on the motor and load together with some 4Cu and that solved the problem; it was a crap shoot really but it worked.



Bob Badger said:


> About a week of testing with me and my crew making different types of changes while groups of engineers with a ton of testing equipment noted what the changes did to the currents.
> 
> They provided us a metal mesh 'sock' that we had to slide over the input and output conductors essentially making a 3-conductor 600 Kcmil VFD cable
> 
> ...


Interesting. Many drives we've put in the line & load were in RMC and in those cases we've still had bearing problems. And when we were forced to run line & load in same RMC (retrofits) we had line PQ trouble & drive trips because of it, but no worse bearing currents. Thanks for the reply.


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## Electric_Light (Apr 6, 2010)

etb said:


> Ah. On all of the smaller drives we put those on, that happened but the current through the load bearings wasn't enough to worry about. I've never worked on a drive that large. We did have a had 40 hp or so with the problem you described. Luckily for us there was a stock size ring that we were able to use on the load as well. We bonded the frames of the rings on the motor and load together with some 4Cu and that solved the problem; it was a crap shoot really but it worked.
> 
> 
> Interesting. Many drives we've put in the line & load were in RMC and in those cases we've still had bearing problems. And when we were forced to run line & load in same RMC (retrofits) we had line PQ trouble & drive trips because of it, but no worse bearing currents. Thanks for the reply.


There's always resin gasket and resin bolt sleeves to provide galvanic isolation at coupler much like mounting TO3 transistors on a heat sink.


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## etb (Sep 8, 2010)

Electric_Light said:


> There's always resin gasket and resin bolt sleeves to provide galvanic isolation at coupler much like mounting TO3 transistors on a heat sink.


Never knew about that particular type but didn't have good luck with the plastic kind nor the rubber spiders on machines where load is supported half by itself and half on motor shaft; rigid coupling is a must and if the coupler causes misalignment you get vibration issues. I'll have to search for those you mention; thanks for the tip!


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## guest (Feb 21, 2009)

Bob Badger said:


> Here is the control for the fans and related scrubers.
> 
> 
> 
> ...


So who's the naughty person who piled stuff on those dry transformers in the first pic? :whistling2:


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