Defective Drive???

hurk27

Senior Member
Actually the IEEE defintion is ASD Adjustable Speed Drive.
wasn't that used for the old variable speed belt drives?, they used to have that on their case.

over the years there have been many variable speed drive but they were mechanical except DC and eddy current drives.

I can remember when soft starts hit the market then VFD (variable frequency drives)
 

Besoeker

Senior Member
Location
UK
wasn't that used for the old variable speed belt drives?, they used to have that on their case.

over the years there have been many variable speed drive but they were mechanical except DC and eddy current drives.

I can remember when soft starts hit the market then VFD (variable frequency drives)
I'm sure Laszlo is correct with his I triple E definition - it's come up here in previous threads.

And you are right. There have been a good many iterations and types of variable speed drive.
I'm old and have had the fortune/misfortune to have been exposed to a fair number of the technologies that have been implemented, some from before I was born far less from since I qualified and got thrown into the deep end. Sink or swim.
Cone pulleys with belt shifters, Ward Leonard, carbon pile differential systems, faceplate regulators, thyratrons mercury archaic rectifiers, SCRs, GTOs, IGBT...stuff.
All of it technology used in adjustable speed drives. From my perspective, the term ASD excludes none of those technologies. A DC drive using a Ward Leonard set up is every bit as mush an ASD as a variable frequency inverter using IGBTs.

We, across the pond, tend to use VSD rather than ASD which I know, from experience, that you have used for decades.
 

Besoeker

Senior Member
Location
UK
20 year old drive: I am surprised the capacitors are still alive. Perhaps time to replace those, although the drives are sooo cheap that it may not be the cost effective solution.
I'm inclined to agree. The suggested fixes may cost more in terms of labour and parts than a replacement. And may just be a short term solution.
High ambient temperatures have been put forward by others as a possible cause of failure but, if the drive trips on start up it wouldn't have got to operating temperature so maybe that suggestion doesn't hold water.

Check the namaplate currents of the motor AND the drive and see if the drive manufacturer constant torque recommended ratios are met.
Distance between motor and drive, motors suitability for inverter use, cable type used, are all potential issues.
Given that the problem has surfaced in the past two weeks, might it be reasonable that those points had been successfully addressed initially rather than becoming a problem after 19 years and 50 weeks?
:p

It maybe time for a new drive.
No argument with that.
 

kwired

Electron manager
Location
NE Nebraska
Hi,

Is it possible that the problem is mechanical and not motor / drive related ?
I am unfamiliar with a " pit drag " so I am guessing but could you have a worn bearing that binds under load or a sprocket / chain issue ?
Stinks to change the drive before your sure.
My thoughts also. If drive is tripping because of overload it is because of output current not because of ambient temperature of the drive, that is typically a different fault code. The dust that was blown out would likely also have triggered a different code instead of "overload" if it was causing a heating issue within the drive. You do not look as dumb when you find the mechanical problem as you do when you replace the drive and next day they call you back and tell you it is doing same thing. Make sure there is no problem with motor bearings, speed reducer, chain, something hanging up in the drag itself - lots of mechanical parts in one of those and maybe if stuck in right place takes extra effort to make it start, make sure drag chain itself has proper tension and is not trying to jump sprockets. Pit is also in area where a lot of moisture collects at times as well as grain making nice place for nasty mess that can rust something, or even find the pit area full of water - just condensation overnight in the leg usually drains into the pit so not having any recent rain means nothing when it comes to finding water in the pit.

"Pit drag" is just a drag style conveyor that pulls grain from the pit (usually dumped from trucks) over to the elevator "leg".

I'd also recommend a new drive. Now's a good time to get the proper drive as well, like mentioned above, one meant for conveyors.
His drive likely will work just fine - may just need parameters set for constant torque instead of variable torque.
 

Electric-Light

Senior Member
Anyone around here use the abbr. VVVF? I think its the most accurate description of drives we have today as they modulate both the V and F to maintain V/Hz ratio.

VFD is something that only changes Hz.

VSD/ASD could mean variable speed ceiling fan that changes speed by altering the amount of slip by varying the torque delivered.
 

gar

Senior Member
120709-0648 EDT

Maybe failing electrolytic capacitors in the drive. Back in that time frame there were a lot of bad capacitors made in the far east. Furthermore even good quality electrolytic capacitors have a shorter life than most other components.

We had a Magnetek drive in a CNC machine that failed as a result of capacitor failure, was maybe a 10 year time. Exchanged for a rebuilt unit at a much lower cost than a new one. Someplace in Chicago was the source. Search the Internet.

.
 

Besoeker

Senior Member
Location
UK
120709-0648 EDT

Maybe failing electrolytic capacitors in the drive. Back in that time frame there were a lot of bad capacitors made in the far east. Furthermore even good quality electrolytic capacitors have a shorter life than most other components.
Twenty years is a reasonable life for electrolytic capacitors.
We are about to change a total of 720 in two fairly big variable speed drives as a precautionary measure. The capacitor banks been in service for about 12 years since they were last replaced.

But I'm inclined to think that replacing the capacitors on a 7.5HP drive might not be an economical fix.
 

Besoeker

Senior Member
Location
UK
You guys are all GREAT!! Thanks so much for the input...
I suppose there must be at least a thousand man years experience and I've got just nine hundred and ninety-nine.........:p
Slightly more seriously, will you let the form know how the problem gets fixed?
 

mike_kilroy

Senior Member
Location
United States
two more ideas to add to the pot:

1) the high heat recently might have caused one (or more) of the 20r old bus caps to fail thus the beginning of overcurrent issues now. As an aside, Can you replace them? we buy these often from digikey for our similar size drive repairs. 20yr old yaskawa 7.5hp drive prob has around 10pc of 750mfd/400v caps that sell for guesstimate $ 40 each. You can offen find bad ones if you unsolder them and measure them on simple capacitance meter..... or new drive is probably better idea.

2) you may have a motor cable that is rubbing against something and it finally frayed thru - again, the high heat makes the insulation softer. if so, as has been stated, it will look bad for you if you replace the drive and the issue remains. we recently had a frayed thru motor cable that passed megger tests but caused overload faults when it moved just right.
 

kwired

Electron manager
Location
NE Nebraska
two more ideas to add to the pot:

1) the high heat recently might have caused one (or more) of the 20r old bus caps to fail thus the beginning of overcurrent issues now. As an aside, Can you replace them? we buy these often from digikey for our similar size drive repairs. 20yr old yaskawa 7.5hp drive prob has around 10pc of 750mfd/400v caps that sell for guesstimate $ 40 each. You can offen find bad ones if you unsolder them and measure them on simple capacitance meter..... or new drive is probably better idea.

2) you may have a motor cable that is rubbing against something and it finally frayed thru - again, the high heat makes the insulation softer. if so, as has been stated, it will look bad for you if you replace the drive and the issue remains. we recently had a frayed thru motor cable that passed megger tests but caused overload faults when it moved just right.
If bus cap is failed will you get a "motor overload" error code or would you get some other error? I would suspect some other error, first guess may be undervoltage error.

Paying attention to exactly what error code is when the drive trips will help solve the issue. If the code is "motor overload" then motor is drawing too much current (according to set parameters anyway).
 

mike_kilroy

Senior Member
Location
United States
True and depends on the drive design.

If drive only has current detection on output side of DC bus only, then yes, overcurrent/overload would not be a valid fault for low bus capacitance; we typically see undervolts fault on these during heavy current draw like quick acceleration.

But there are drive designs that watch current feeding the dc bus: these have been known to show overcurrent faults.
 

jerjwillelec

Senior Member
Location
Nevada, IA
The error code is "over current"... The manual gives some troubleshooting steps to take...one being, reprogram the acceleration time. It's the inconsistancy of the failing that gets me...some times loaded, sometimes not...sometimes at full speed, sometimes at lowest speed...sometimes at start up, sometimes after several seconds of run time. The voltage readings I get are always in the 490's and the FLC always reads around half of the motor nameplate.

Nameplate:
220/440 VAC
19.2/9.6 FLA
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Engineer
The voltage readings I get are always in the 490's and the FLC always reads around half of the motor nameplate.

Nameplate:
220/440 VAC
19.2/9.6 FLA
Are you using a meter on the output of the drive, or are your reported values from the drive display?

Does the nameplate on your motor really say 220/440V? That is a pretty old motor to be using on a PWM style VFD.
 

kwired

Electron manager
Location
NE Nebraska
Has it been driving same motor and load for some time or is something recently changed? Have you checked mechanical conditions of load - maybe it is early sign of a failure within the driven load.

Just changing the drive because it is older is nothing more than throwing parts at it in hopes the problem will go away. If there is a problem with something else the problem will not go away.
 

jerjwillelec

Senior Member
Location
Nevada, IA

jerjwillelec

Senior Member
Location
Nevada, IA
Has it been driving same motor and load for some time or is something recently changed? Have you checked mechanical conditions of load - maybe it is early sign of a failure within the driven load.
To the best of my knowledge...nothing has changed in 20 years

Just changing the drive because it is older is nothing more than throwing parts at it in hopes the problem will go away. If there is a problem with something else the problem will not go away.
I realize this...that is why I'm here seeking all of your advice
 

Besoeker

Senior Member
Location
UK
To the best of my knowledge...nothing has changed in 20 years



I realize this...that is why I'm here seeking all of your advice
I think most of us here who have had experience in the drives field are suggesting replacing the unit.
It's a relatively low cost item and, having seen your pics, the accumulation of dust probably hasn't done the original unit a whole lot of good.
Don't faff around - just replace it.
And try to make sure that the new unit is better protected against the ingress of all that karp.
 
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