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Author Topic: Protect equipment from excess voltage  (Read 9431 times)

Don Davis

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Protect equipment from excess voltage
« on: April 06, 2015, 05:09:17 pm »

Forgive this nube question but is there any way to build an alarm that will sound if the voltage to an amp rack or distro is too high? Or shut down to protect the system kind of like over current protection but for voltage level instead.

I ask because I had a bad experience this past weekend. The DWP of a military base provided 150KW genny for the Easter production I was providing for. They provided the generator and Cal50 cabling up to my 50A single phase distro and a stand by operator. My assistant who is a registered electrician, assisted the DWP tech with the hook up. He watched the tech take a meter out and check the genny output then give a thumbs up to energize the system.

Part way into sound check one of the monitor amps goes down. Assuming a normal failure I brought out the spare amp and rewired. About 15 minutes to curtain Iím at FOH and someone runs back and says smoke is coming out of one of the amps. I immediately got that sick feeling in my stomach and knew what was happening. I started powering down then ran and got the tech out of his truck and told him heís frying my equipment. He got his meter out and it reads almost 200V per leg.

He simple didnít set it up correctly. Iím not sure what he checked with the meter since I was out front managing the set up at the time.

I know this is my fault for not verifying what this tech metered and the words Iíve heard on this forum many times about metering before you power up were blasting in my head but in the heat of battle with a tight set up schedule stuff happens so please donít beat the crude out of me for my mistake.

Besides never taking ANYONEís word on power ever again, what else would you guys suggest. I do have voltmeters installed in the backs of my main amp racks but when theyíre tucked away they canít be seen. How about a strobe, bell etc. something to get my attention possibly for over or under proper voltage. I lost 2 - XTI4000s and possibly an iTech4000 so far that I know of. Iím grateful it didnít take out any FOH gear or all the bandís backline. All my amps are set up to run on 120V/15-20A.
Thanks
Don
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TJ (Tom) Cornish

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Re: Protect equipment from excess voltage
« Reply #1 on: April 06, 2015, 05:25:28 pm »

Forgive this nube question but is there any way to build an alarm that will sound if the voltage to an amp rack or distro is too high? Or shut down to protect the system kind of like over current protection but for voltage level instead.

I ask because I had a bad experience this past weekend. The DWP of a military base provided 150KW genny for the Easter production I was providing for. They provided the generator and Cal50 cabling up to my 50A single phase distro and a stand by operator. My assistant who is a registered electrician, assisted the DWP tech with the hook up. He watched the tech take a meter out and check the genny output then give a thumbs up to energize the system.

Part way into sound check one of the monitor amps goes down. Assuming a normal failure I brought out the spare amp and rewired. About 15 minutes to curtain Iím at FOH and someone runs back and says smoke is coming out of one of the amps. I immediately got that sick feeling in my stomach and knew what was happening. I started powering down then ran and got the tech out of his truck and told him heís frying my equipment. He got his meter out and it reads almost 200V per leg.

He simple didnít set it up correctly. Iím not sure what he checked with the meter since I was out front managing the set up at the time.

I know this is my fault for not verifying what this tech metered and the words Iíve heard on this forum many times about metering before you power up were blasting in my head but in the heat of battle with a tight set up schedule stuff happens so please donít beat the crude out of me for my mistake.

Besides never taking ANYONEís word on power ever again, what else would you guys suggest. I do have voltmeters installed in the backs of my main amp racks but when theyíre tucked away they canít be seen. How about a strobe, bell etc. something to get my attention possibly for over or under proper voltage. I lost 2 - XTI4000s and possibly an iTech4000 so far that I know of. Iím grateful it didnít take out any FOH gear or all the bandís backline. All my amps are set up to run on 120V/15-20A.
Thanks
Don
Your ITech should be OK - it's universal voltage.

The big lesson here is you need to test under load.  Presumably the neutral conductor was either disconnected or poorly connected, which causes the voltages to change based on the relative loads on the phases.  A load test will reveal that.  Get a couple 1000W PAR cans or heaters and plug them in to the same phase of your distro.  If you can vary the voltage more than a couple volts, you have a problem.

Not that this is a huge consolation, but you should work to powering as much of your gear at 240/208v as possible.  In addition to balancing the load which helps generators out a lot and preventing harmonics on the neutral wire, you will never lose gear to a lost neutral wire in the future, as your gear isn't using the neutral.
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Frank DeWitt

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Re: Protect equipment from excess voltage
« Reply #2 on: April 06, 2015, 05:27:31 pm »

You can buy voltage sensor relays and set them to close a contact at what ever voltage you chose.  The contact could ring a bell or light a light or disconnect the power to your gear. 

You can also get equipment from SurgeX and others that includes under and over voltage shutdown

Under-Voltage Auto Shutdown  Adjustable from 90V to 110V   
Over-Voltage Auto Shutdown  Adjustable from 130V to 150V

http://surgex.com/products/rackmount-sequencers-product-line.html
   
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Mike Sokol

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Re: Protect equipment from excess voltage
« Reply #3 on: April 06, 2015, 05:34:22 pm »

Forgive this nube question but is there any way to build an alarm that will sound if the voltage to an amp rack or distro is too high? Or shut down to protect the system kind of like over current protection but for voltage level instead.

I've never seen anyone do this for pro-sound, but it's a common problem with the RV industry. Progressive Industries makes a EMS (Electrical Management System) with relays that will monitor voltage and ground, and disconnect you from power if something goes out of spec (over 140 volts, I think). They make one rated up to a 50-amps at 120-240 volts with a 50-amp "stove" connector. I might consider something like this for my own sound rig if I was doing a bunch of shows powered from military generators. Even if the neutral opens up in the middle of a show, the EMS Surge Guard will open up the relay contacts to protect your gear.

http://www.progressiveindustries.net/

As a side note, none of these EMS products will detect or disconnect you from a RPBG (Reverse Polarity Bootleg Ground) outlet. But that's nearly impossible to create on a 120-240 split phase feed.   
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John Roberts {JR}

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Re: Protect equipment from excess voltage
« Reply #4 on: April 06, 2015, 05:53:16 pm »

Life is cruel teacher.... she gives the test first and then the lesson... Learn from this grasshopper...

JR
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Don Davis

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Re: Protect equipment from excess voltage
« Reply #5 on: April 06, 2015, 06:48:25 pm »

Life is cruel teacher.... she gives the test first and then the lesson... Learn from this grasshopper...

JR

Yes JR it is. One would think at my age the lessons would be diminishing but they seem to get more expensive.
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Don Davis

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Re: Protect equipment from excess voltage
« Reply #6 on: April 06, 2015, 06:54:47 pm »

Your ITech should be OK - it's universal voltage.

The big lesson here is you need to test under load.  Presumably the neutral conductor was either disconnected or poorly connected, which causes the voltages to change based on the relative loads on the phases.  A load test will reveal that.  Get a couple 1000W PAR cans or heaters and plug them in to the same phase of your distro.  If you can vary the voltage more than a couple volts, you have a problem.

Not that this is a huge consolation, but you should work to powering as much of your gear at 240/208v as possible.  In addition to balancing the load which helps generators out a lot and preventing harmonics on the neutral wire, you will never lose gear to a lost neutral wire in the future, as your gear isn't using the neutral.

The tech did mumble something about a loose wire, probably the neutral as you suspect.

One channel on an iTech was cutting in and out for the balance of the event. To the shop it goes.
I don't believe the XTIs are dual voltage capable. I currently have 6 in my mix racks.
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Don Davis

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Re: Protect equipment from excess voltage
« Reply #7 on: April 06, 2015, 07:03:22 pm »

You can buy voltage sensor relays and set them to close a contact at what ever voltage you chose.  The contact could ring a bell or light a light or disconnect the power to your gear. 

You can also get equipment from SurgeX and others that includes under and over voltage shutdown

Under-Voltage Auto Shutdown  Adjustable from 90V to 110V   
Over-Voltage Auto Shutdown  Adjustable from 130V to 150V

http://surgex.com/products/rackmount-sequencers-product-line.html

Looks like a good solution but might be too pricey for multiple circuits
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Don Davis

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Re: Protect equipment from excess voltage
« Reply #8 on: April 06, 2015, 07:06:35 pm »

I've never seen anyone do this for pro-sound, but it's a common problem with the RV industry. Progressive Industries makes a EMS (Electrical Management System) with relays that will monitor voltage and ground, and disconnect you from power if something goes out of spec (over 140 volts, I think). They make one rated up to a 50-amps at 120-240 volts with a 50-amp "stove" connector. I might consider something like this for my own sound rig if I was doing a bunch of shows powered from military generators. Even if the neutral opens up in the middle of a show, the EMS Surge Guard will open up the relay contacts to protect your gear.

http://www.progressiveindustries.net/

As a side note, none of these EMS products will detect or disconnect you from a RPBG (Reverse Polarity Bootleg Ground) outlet. But that's nearly impossible to create on a 120-240 split phase feed.

The EMS-HW50C looks very interesting and may provide distro level protection. We are almost exclusively on military bases. Sometime on generators sometimes on house power.
I bought my own generator last year to help prevent these problems but it isn't big enough for the rig I used this past weekend.
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Mike Sokol

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Re: Protect equipment from excess voltage
« Reply #9 on: April 06, 2015, 07:26:49 pm »

The EMS-HW50C looks very interesting and may provide distro level protection. We are almost exclusively on military bases. Sometime on generators sometimes on house power.
I bought my own generator last year to help prevent these problems but it isn't big enough for the rig I used this past weekend.

Yeah,  the EMS-HW50C is the hardwired version, so you can put your own connectors on it that would plug right into your distro from genny power. They've tested these units all the way up to plugging them into a 480-volt generator (the first time it was accidentally on an oil-field generator) and it just shuts off the output power and shows over-voltage without damaging itself. I have both the 30-amp/120-volt and 50-amp//120/240-volt versions in my shop which Progressive Industries sent me last year to evaluate, and I've not been able to blow them up yet. ::)

I'm sure the PI-EMS would shut down AC power with a reset time-out if the neutral failed on your generator feed or it went over-voltage on one of the legs for any other reason. Let me know if you want to talk to their engineering department about your application and I'll hook you up. 

FYI: The street price is around $350 including shipping. http://www.amazon.com/Progressive-Industries-HW50C-Electrical-Management/dp/B003AN1UA8
« Last Edit: April 06, 2015, 07:29:24 pm by Mike Sokol »
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Mike Sokol
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Re: Protect equipment from excess voltage
¬ę Reply #9 on: April 06, 2015, 07:26:49 pm ¬Ľ


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