Voltage Spike Suppressors for 480Vac Control Board

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dquinch

New member
Location
sacramento, ca
Hi! I'm quite new to this forum and i appreciate having this kind of tool to help each and everyone out there in troubleshooting equipments may it be household or inductrial.

I have one issue i would like to bring up to everyone. We have an SCR Pack (Firing Pack) we use to control the Temperature for our Ovens. The Firing Pack is a Phasetronics EZ2 Series. Recently, we encounter a major breakdwon with the Control Boards Failing. This happened when the Utility company tried to switch us to a backup substation. As a result, we had three Control boards failing.

Is there any filter or voltage suppressor we can place in line to avoid this from happening again?

Thanks in advance for your help.
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
Is the 480 source 3 phase or single phase? If it's 3 phase, is it grounded Wye or Delta. If Delta, is it corner grounded or ungrounded? The reason I ask is that during switching, the POCO can single phase the primary. If that happens on an ungrounded Delta, the phase to phase voltages of the Delta secondary can spike very high. A surge suppressor could fail if the condition existed for very long (ours did). Grounding the Delta stops this. There are other issues with corner grounded 480, but that may be an option. 480/277 grounded Wye is the best solution. I can't see why switching substations would cause you a problem unless they single phased. A phase monitor relay is another option, but it won't work on ungrounded Delta. We fried several when single phase switching the primary of ungrounded Delta banks. That solution was to use a temporary corner grounding jumper (called a "firecracker") during switching.

We chose not to permanently ground the bank. Lots of controversy over whether or not you should.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
That unit is not particularly ruggedly built. Their primary market is power controllers for the semiconductor industry, who are required to have the cleanest and most stable power available. That unit is built based on expecting that sort of power, the glitches and hick ups that come along in every day industry are more than it can take. The firing board has a voltage sensing circuit on it so that it knows when to fire the SCRs. That sensing circuit has a "snubber circuit" on it that tries to protect it from damaging spikes, but they basically only work once in a really bad one, then they are gone. Invest in a really good surge protective device, one that comes with indicators that tell you that it is no longer there after a surge. Some have simple LED indicators, but you must remember to look. As you go up in cost, you get ones that can close a contact so that you can send a signal telling someone it has failed. Most likely though, the SPD will cost as much or more than that EZ 2.
 

templdl

Senior Member
Location
Wisconsin
Hi! I'm quite new to this forum and i appreciate having this kind of tool to help each and everyone out there in troubleshooting equipments may it be household or inductrial.

I have one issue i would like to bring up to everyone. We have an SCR Pack (Firing Pack) we use to control the Temperature for our Ovens. The Firing Pack is a Phasetronics EZ2 Series. Recently, we encounter a major breakdwon with the Control Boards Failing. This happened when the Utility company tried to switch us to a backup substation. As a result, we had three Control boards failing.

Is there any filter or voltage suppressor we can place in line to avoid this from happening again?

Thanks in advance for your help.
Sounds to me that you are on the receiving end of a slightly out of phase transfer. When there is a transfer from one source to another the must be synchronized in phase and if not you will get a voltage spike. The transfer either must be synchronized or there should be anough time delay neutral to allow the system to settle down where any inductive loads can die down as and counter EMF that they generate will be minimum enough as to not affect a transfer back to the alternate source.
Do you have any idea as to what the magnitude of the voltage spike is? Also, there are instances where switching a PFFCs also can cause spike.
 

ATSman

ATSman
Location
San Francisco Bay Area
Occupation
Electrical Engineer/ Electrical Testing & Controls
SPD Theory

SPD Theory

Interesting discussion. I have attached a file, although not directly addressing the OP,
I feel is valuable info on the subject of SPD's.
The file was taken from an email string that was edited so read from the bottom up.

Tony
 

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