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Old 12-04-2009, 07:23 PM
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Default Todays Worthless Time Consuming Job - Yet Another VFD Failure

We sell a brand of boilers (that shall remain nameless, to protect the guilty), that lately have had their share of service/parts problems. I was called out to a jr-high school, with a boiler in alarm, from the fault codes and the smell, it became apparent it was another motor/VFD failure. This make about at least 2 dozen of these failures, over the last 6-8 months, in our service area The VFD manufacturer also manufactures the motor, this is an inverter VFD, single phase 230 vac single phase in and 220 vac 3 phase out, the truly bad part is there doesn't seem to be any early warning of disaster, they just go bang. The manufacturer is one of the worlds largest electrical concerns and had been making VFDs for over 40 years, in many forms, and they are completely baffled. This particular VFD is factory programed, and the basic program is locked, with only about 10 variables that are field changeable ( we don't change them, they are left at factory defaults). They are sending a new motor and VFD, its about a 3 hour change out and at this point I can't guaranty it will last until I get to the end of the drive way.

I install VFDs all of the time and failures are not uncommon, usually because of wrongful applications, wrong types of motors or operational issues, but this boiler package was designed from the beginning as a package and to this point nothing concrete has shown up as the cause of the failures. There is nothing harder in the world to tell a customer it has failed, they sending new parts and you hope it cures the problem.
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Old 12-04-2009, 08:13 PM
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I feel for you Jack, having to tell the customer that there is a failure and it is your equipment. That is a bummer for sure.
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Old 12-04-2009, 08:39 PM
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Jack is it a powerflex drive?

I won't name the mfg either. You will know or you won't know.

Scott
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Old 12-04-2009, 08:40 PM
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What size motor ?
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Old 12-04-2009, 08:53 PM
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Quote:
Originally Posted by Scotts View Post
Jack is it a powerflex drive?

I won't name the mfg either. You will know or you won't know.


Scott
No, not a powerflex, its a European unit

Quote:
Originally Posted by GWIZ View Post
What size motor ?
The sizes of the motors have varied, the one today was 1.25 hp


jack
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Old 12-04-2009, 09:23 PM
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I suppose there are several of these units of different hp & configuration in each boiler installation so it'd be impractical for the customer to keep a backup on hand?
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Old 12-04-2009, 09:37 PM
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Quote:
Originally Posted by platypus20 View Post
No, not a powerflex, its a European unit



The sizes of the motors have varied, the one today was 1.25 hp


jack
close enough. Are these units equipped with a cooling fan on the drive? If they are they may have their very own drive to regulate the speed of the cooling fan. A drive within a drive so to speak. The drive is sized very close to size of the application. Actually the drive depends on the cooling fan to cheat a little on the size and cost. Several of these at our home office have melted down due to the drive for the cooling fan going out and thus toasting the drive in quite the short order.

The OEM out there just gave up and supplied a drive from a different manufacturer. Issue resolved.

Scott
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Old 12-04-2009, 10:10 PM
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There may be a way to find out the problem. There is a type of breaker made for 3 phase, we used them on Flygt pumps alot...that trips out on any phase imbalance. (prevents 2 phasing, the death blow to motors.
If this was installed between the VFD and the motor, you could find out fast if the motor was failing and destroying the VFD, or the VFD failed and the motor was okay.
They always tell you to switch the VFD only, but this would only activate on failure of one or the other component.
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  #9  
Old 12-05-2009, 09:43 AM
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Quote:
Originally Posted by Ironman View Post
If this was installed between the VFD and the motor
Gerry, someone correct me if I'm wrong but I was always under the impression that any switching device between the VFD and the motor would kill the VFD in short order.
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Old 12-05-2009, 12:53 PM
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Quote:
Originally Posted by rmack898 View Post
Gerry, someone correct me if I'm wrong but I was always under the impression that any switching device between the VFD and the motor would kill the VFD in short order.
Yes, you are right.
I'm not saying use the switch as a shut off device. I'm saying use it's phase loss protection system. If this thing trips, you are already in trouble. You have lost a motor or a phase from the VFD.
So it's tripped ....measure voltage on the VFD...is it toast? If not....measure the motor windings....is it toast?
At this point you can determin if the motor is failing every time ...or the VFD

Some motors are not rated for VFD service...and this may be killing the motor and the VFD.
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