VFD surge protection?

[jmjr55]

We have an Atlas Copco ZT 55VSD air compressor. About a month ago we had a utility power surge. Which caused quite a bit of havoc in our facility. But the most costly event was the VFD in our Atlas Copco compressor, the VFD was destroyed. Atlas came out and they replace the VFD. Their recommendation to protect the VFD in the future is the addition of a fused dissconect with very fast acting Bussmann type T fuses, JJS Series. I had our electrical sales rep. come out to price this up and he explained that it would be worth looking into a constant voltage transformer (CVS Hardwired Series) made by SOLA HD.
Has anyone had experience with VFD protection and what did you find worked the best? Cost is a factor the, constant voltage transformer is about 50% more but I am looking for the most reliable and best protection. Since saving $500 now and a new VFD was $10K I'd rather spend the extra $500 not to mention the down time.
Thanks, for your feed back.

 

[kwired]

We have an Atlas Copco ZT 55VSD air compressor. About a month ago we had a utility power surge. Which caused quite a bit of havoc in our facility. But the most costly event was the VFD in our Atlas Copco compressor, the VFD was destroyed. Atlas came out and they replace the VFD. Their recommendation to protect the VFD in the future is the addition of a fused dissconect with very fast acting Bussmann type T fuses, JJS Series. I had our electrical sales rep. come out to price this up and he explained that it would be worth looking into a constant voltage transformer (CVS Hardwired Series) made by SOLA HD.
Has anyone had experience with VFD protection and what did you find worked the best? Cost is a factor the, constant voltage transformer is about 50% more but I am looking for the most reliable and best protection. Since saving $500 now and a new VFD was $10K I'd rather spend the extra $500 not to mention the down time.
Thanks, for your feed back.

I have to ask if you had a transient voltage condition or a sustained condition. Surge protection will bleed transients off but if you have an overvoltage condition for any significant amount of time you likely will still suffer damage. Transients would be something fairly normal that happens when large loads are switched on or off either on site or on the POCO system or when lightning strikes - even if a few miles away. The sustained condition is more rare and will happen when something on the system is damaged or malfunctions, like an event that causes an open neutral. Protection from this may be better accomplished with voltage monitoring relays, along with surge protection for the transients. Just a thought.

 

[GBShade684]

I completely agree with kwire. But if it is a transient, since you are using Bussmann fuses, you may want to consider their SPDs also. It's a product I am fairly familiar with and I have seen it used with good results. PM me is you would like more info.

 

[jmjr55]

This was an electrical storm with a very short power surge. Short enough it was not evident to all that it even happened.
Thanks

 

[Jraef]

Wow.

Do NOT put a Sola CVS ahead of a VFD! Your supplier is a nincompoop, stop asking him questions, he is just trying to waste your money by selling you something that is not just over kill, but may actually do harm! A Sola CVS is a Ferroresonant Transformer. When put in front of a highly non-linear load like a VFD diode front-end rectifier, it will clip the tops off of the sine waves. But the VFD draws it's power from the tops of the sine waves, so the result is you will LOWER the capacity of the VFD, or you must increase the size of the CVS by a factor of at least 2X. When you do that, the efficiency of the CVS can go down to as low as 60%, so you will convert that lost energy into heat in the CVS, which, in some cases, ALSO will increase your Air Conditioning costs. Bad bad bad all around, plus it will NOT protect you from the kind of thing you experienced anyway.

What you want is a very good surge protective device (SPD), preferably one that is Type I or at least Type II (the numbers are better if lower) and provides indication when it has worked and when it has failed or is about to. A surge counter is an even better idea as well because they will give you guidelines on roughly when to expect to replace it. All SPDs are inherently sacrificial devices, but the cheaper you go, the sooner they blow (so to speak). I've been using the XBS Series from Advanced Protection Technologies lately, they have been good. But any Class I is going to be good and like I said, at least Class II. Class I means it can take an almost direct lightning strike, Class II means "remote" and class III is only good for "far away", which I define as being in another state (but I'm on the west coast, so if you are in Rhode Island, that doesn't mean much). Don't waste money on a Class III or one that fails to mention the protection class, because that means they didn't even pass Class III and are worthless.

In addition, add a Line Reactor to the VFD. A Line Reactor adds what is called an "inductive time constant" to the input of the VFD. This means that the voltage and current can only increase at a certain rate, which allows other protection features to have time to react rather than blow up. Line reactors are what I call "cheap insurance" for VFDs. They are MUCH simpler and cheaper than a CVS but don't have the other problems. 3% reactors minimum, 5% if you can afford them and fit them. If you were considering a CVS, expect to pay 1/4th that amount for even a 5% reactor. Spend the extra on as good an SPD as you can find.

 

[jmjr55]

Thanks for the info!

Thanks for the info!

Thanks for the info, Jraef; I will be taking your info for a good direction to go with alleviating this potential problem on our VFD drives.

 

[robbietan]

In addition, add a Line Reactor to the VFD. A Line Reactor adds what is called an "inductive time constant" to the input of the VFD. This means that the voltage and current can only increase at a certain rate, which allows other protection features to have time to react rather than blow up. Line reactors are what I call "cheap insurance" for VFDs. They are MUCH simpler and cheaper than a CVS but don't have the other problems. 3% reactors minimum, 5% if you can afford them and fit them.

I agree here. voltage sags in a facility often mean a current surge that affects VFD operation. a line reactor can protect a VFD against this. and adding reactors will also reduce harmonics coming from the VFD