vfd blowing up

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Pete Benoit

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I recently finished a office warehouse for a large mech contractor.In the past 3 weeks 2 small honeywell NXL one hp drives have exploded,tripping out the main breaker on the boiler room and thus all the heat in the building{in floor radiant} These drives run one hp prem. eff. pump motors and the other drives in the building are larger and have not had any problems yet.The building has a leibert interceptor tvss.They are asking me why this is happening and I just do not have an explanation.I told them today they may have design issues and it did not go over well .Could faulty programing cause a failure like this ? any help would be greatly appreciated
 
I would check the rating of the drives versus the motor being controlled. Also check if the motor is inverter duty rated. The min/max freq parameters should be checked on drive also to make sure it isnt being worked to hard. Ambeint temp could come into play also.
Question,why isnt the o/l protection at the drive not going instead of the main breaker?
 
Travis, the main and branch are tripping due to the fault that occurs when it blows.Its a one HP drive and a one HP motor, there are two of these in the room and they both self destructed.they told me that prem. eff.motors are inverter rated. its warm in the room but I would think it would trip out on overtemp if this were the problem,it should trip out or shutdown on on any number of faults before it self destructs,I did not provide them or program them. Is it possible they were trying to run them to slow or fast? I have no other problems in this building
 
Pete Benoit said:
Travis, the main and branch are tripping due to the fault that occurs when it blows.Its a one HP drive and a one HP motor, there are two of these in the room and they both self destructed.they told me that prem. eff.motors are inverter rated. its warm in the room but I would think it would trip out on overtemp if this were the problem,it should trip out or shutdown on on any number of faults before it self destructs,I did not provide them or program them. Is it possible they were trying to run them to slow or fast? I have no other problems in this building
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I would not lean towards a programming issue or an overload at the motor being the problem. I have not dealt with this brand of drive specifically but if it is "blowing up" and tripping the main it sounds like the caps on the line side are going. This would occur due an imbalance on the line side of the drive. The drive itself should handle all overloads on the load side although it is possible to have the overload setting to high prematurly causing damage to the drive. Has the load been tested for shorts? I have seen a shorted motor and/or wiring take drives out causing the main supplying the drive to trip before. If the motor and wiring tests ok monitor the bus voltage of the drive if possible with this brand and check for large flucuations 480vac should be around 600vdc bus and 240vac should be around 300vdc bus. You may need to put a line reactor in place if this is the problem.
 
Are these installed on a high resistance ground or ungrounded system? If they are then check the instruction manual. I am not sure about these particular drives but I know AB Powerflex drives have MOV's that need to be removed. If you don't they will fry.
 
eric9822 said:
Are these installed on a high resistance ground or ungrounded system? If they are then check the instruction manual. I am not sure about these particular drives but I know AB Powerflex drives have MOV's that need to be removed. If you don't they will fry.
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Good point totally slipped my mind they have a jumper that needs removed to disconnect the MOV's. In this case it has you disconnect them if line to ground voltages on any phase may exceed 125% of line to line voltage.
 
Pete Benoit said:
I recently finished a office warehouse for a large mech contractor.In the past 3 weeks 2 small honeywell NXL one hp drives have exploded,tripping out the main breaker on the boiler room and thus all the heat in the building{in floor radiant} These drives run one hp prem. eff. pump motors and the other drives in the building are larger and have not had any problems yet.The building has a leibert interceptor tvss.They are asking me why this is happening and I just do not have an explanation.I told them today they may have design issues and it did not go over well .Could faulty programing cause a failure like this ? any help would be greatly appreciated
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I think the Honeywell NXL is a rebadged Vacon product. Assuming that it is, here's a link to the manual:
http://www.vacon.com/Default.aspx?id=450403&FileView=462796
Note pages 1 and 8.
Also, check the voltage rating of the drive. The NXL has two ranges, 208-240V and 380-500V. For European use, the part number for a 0.75kW (1 hp) 208V unit would start with NXL 0003 2. For the higher voltage it would be NXL 0002 5. Maybe Honeywell use the same numbering system.

As system integrators, we have supplied hundreds of Vacon drives with only one problem that I know of - and that was when the customer left it outside in the rain...
That you have had two fail in the same location within such a short period suggests a system problem.
If the fault takes out the main breaker then, as Travis noted, the local fault protection for the drives is probably incorrectly sized.
 
Pete Benoit said:
(cut)In the past 3 weeks 2 small honeywell NXL one hp drives have exploded,tripping out the main breaker (cut)
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The term, "exploded" tells me there likely are broken drive pieces visible. Where did the drive break? Front end? Inverter? control board?

This will certainly give some clues as to what caused the malfunction?

cf
 
eric9822 said:
Are these installed on a high resistance ground or ungrounded system? If they are then check the instruction manual. I am not sure about these particular drives but I know AB Powerflex drives have MOV's that need to be removed. If you don't they will fry.
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Not all drive manufacturers use these MOV's. AB does for sure. I agree this should be checked first. The only time they need to be removed is when you have a center tapped ground wye connected system, (AB's exact words) which is unusual as most manufacturers insist this type of xfmr secondary is what they prefer.

What part of the drive is blowing up? Input bridge? IGBT's? What has the manufacturer said? You need to get them involved and let them do the explaining to the customer. They are the experts on their products, let them prove it.
It could be as simple as a bad run of rectifier bridges. The manufacturer needs to be notified ASAP.
 
John Valdes said:
The only time they need to be removed is when you have a center tapped ground wye connected system, (AB's exact words) which is unusual as most manufacturers insist this type of xfmr secondary is what they prefer.
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Where do you see that? Page 1-13 of the manual I have says "PowerFlex 700 drives contain protective MOV's and common mode capacitors that are referenced to ground. To guard against drive damage, these devices must be disconnected if the drive is installed on a resistive grounded system or an ungrounded distribution system where line-to-ground voltages on any phase could exceed 125% of the nominal line-to-line voltage."
 
eric9822 said:
Where do you see that? Page 1-13 of the manual I have says "PowerFlex 700 drives contain protective MOV's and common mode capacitors that are referenced to ground. To guard against drive damage, these devices must be disconnected if the drive is installed on a resistive grounded system or an ungrounded distribution system where line-to-ground voltages on any phase could exceed 125% of the nominal line-to-line voltage."
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Thats exactly what mine says!
 
I do not have the AB manual. I read it on this forum not long ago. Mountain Man had a similar issue and explained that AB made the statement. This is one reason I do not like AB drives. They are flimsy.
Put in a Yaskawa and be done with it.
In Mountain Mans post he had several AB's fried. While he had several Yaskawas that did not even flinch. AB told him to remove the jumpers and referenced the wye connection as the culprit. Sorry I posted with out first hand knowledge.
 
I don't have any experience with Honeywell drives but did have an issue with some Honeywell burner managment units a number of years ago. The MOV's in the input blew (unknown reason) but rather than remaining open one shorted one leg to equip. cabinet. Cabinet was not properly bonded to ground. This put 208 across the input and realy smoked em.Fairly new install and no one had bothered to make sure it was realy bonded to ground!!
 
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