ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 2 [3] 4 5   Go Down

Author Topic: Testing Generator Voltage  (Read 19784 times)

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2244
Re: Testing Generator Voltage
« Reply #20 on: May 30, 2014, 10:13:41 pm »

The OP mentioned having trouble testing voltage in a twistlock receptacle-14-50Rs and 14-30Rs can be just as bad-don't rely on a meter test to check for live before disassembly.

That said, a method I have used is a spare male plug that is not connected to a cord.  The Hubbel ones are more or less finger safe-though I would wrap tape around the screws for insurance.  I would also only plug/unplug with the genny off or main disconnect thrown. You can then use the holes intended for wire as test points. Keep in mind this is still "live work" and proper safety precautions observed, but if I were setting up/testing gennies on a regular basis, I think I would keep a "test" plug handy.  IMO safer and more reliable than probing a TL or high capacity receptacle. 
Logged
Steve Swaffer

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Offline Offline
  • Posts: 3417
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: Testing Generator Voltage
« Reply #21 on: June 08, 2014, 02:52:31 pm »

So I discovered something new with the "newer" control panels on WhisperWatts- at the Relay for Life I did Friday, they had a locally provided 45kW from a reputable local supplier (that never grounds their gennies, but that's a different story!). On the control panel, there was an Engine Speed switch, high speed and low speed. The tech who delivered it (I wasn't there for the drop) had switched it to low speed. When I metered the genset before use, I found 70v/150v instead of 110/220v! By switching the Engine Speed back to normal (high speed) the voltages increased to normal as well.

When the rental tech was picking it up yesterday morning, I told him about this, and he was surprised that this lowering of speed also lowered the voltage. He said he'll speak to their engineers... but first--

Has anyone encountered that same switch on a diesel generator?
Is it supposed to reduce the voltage along with the engine speed (I feel like it's supposed to be like the "Eco-throttle" on Honda EU generators?), or was that control malfunctioning on this unit?

Does it just seem like a stupid thing to have? Haha.

-Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

John Moore

  • Full Member
  • ***
  • Offline Offline
  • Posts: 223
  • "learning the hard way sucks donkey kong"
    • Trinity Productions
Re: Testing Generator Voltage
« Reply #22 on: June 08, 2014, 03:08:46 pm »

Had the same issue on one in Feb this year...freaked me out... !   flipped the switch and all was good.. we could only dial in so much voltage gain on the unit, once flipped, we had MORE than enough power...and yes, we ground all our generators, it is Code here on the left coast.
Logged
http://www.trinityprosound.com 209-832-8023
DEALER:Dealer for Yorkville, EV, QSC, RCF, Danley Sound Labs, VTC, Allen & Heath, Ashly, Denon,  Audix, One Systems, Beyerdynamic, Presonus, K&M, Ultimate,  Trusst, Road Ready, Gator, Radial Engineering, Turbosound, dB Technologies, RCF, American Audio,  Rapco, CBI Cables, ADJ, Chauvet, Blizzard, Furman, Shure, Tascam, Elite Screens,  BenQ, Midas, Digico,  and many many more...

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Offline Offline
  • Posts: 3417
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: Testing Generator Voltage
« Reply #23 on: June 08, 2014, 03:12:08 pm »

Had the same issue on one in Feb this year...freaked me out... !   flipped the switch and all was good.. we could only dial in so much voltage gain on the unit, once flipped, we had MORE than enough power...and yes, we ground all our generators, it is Code here on the left coast.

Code is, of course, state by state, and dependent on your AHJ -- in Seattle, permits are required to be pulled on anything over 5k, with an inspection, but that's anywhere from $90.50 to $271.50 (business hours or not) - and some of my clients don't bother. I'm not in power full time, so I will provide the gennie and ground it as needed, but I let the clients know they are responsible for obtaining the needed permit and scheduling the inspection. Since the inspector(s) will leave the signed off electrical permit after they've been there... I know damn well who has and who has not done this. :) I ensure, though, that everything I do is by the book and up to code.

But yeah, I had the same thing-- cranked up the voltage gain, little change, but then hit that switch and life was good!

-Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Offline Offline
  • Posts: 3417
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: Testing Generator Voltage
« Reply #24 on: June 08, 2014, 03:22:24 pm »

Something else I just wondered... so rental co brings out diesel, doesn't ground it. Would you insist they come back and do so? In my case, they were long gone when I arrived, and I was just using the 50A twistlocks to spider boxes. Would you carry a rod and sledge and just drive one in? (I am certain what would have pissed off the high school that would now have a copper pole jammed in their field. Haha.)

-Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2244
Re: Testing Generator Voltage
« Reply #25 on: June 08, 2014, 06:16:07 pm »

Who hired the rental company?  If you are just plugging into power hired/provided by the venue, I would think your liability would be minimal.

Is there a local inspection requirement?  Frankly, I view inspectors as my friend-they come in handy as the "bad guy" that insists things are done by the book.

As has been discussed on other threads, ground rods are mainly lightning protection.  I would be more concerned about bonding-equipment/stages/etc myself.  Also, if GFCI protection s used there is a measure of safety should a path accidentally be created back to the genny.

That said, grounding is required by the NEC, so if power is my responsibility and I am going to use this vendor in the future, it wouldn't hurt to establish that "If we are setting up for Ray, make sure you ground the genny, we don't want to make an extra trip." 

Also, ground rods are often surprisingly easy to pull.  (I have hit more than one old foundation 7 to 7 1/2 feet down!)  And in soils around here at least, a little water can be used an you can work the ground rod in easier than using a sledge.  Though this reminds me of another experiment Mike was working on for a temporary grounding electrode-but that is another thread.
Logged
Steve Swaffer

jason misterka

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 282
Re: Testing Generator Voltage
« Reply #26 on: June 08, 2014, 09:11:00 pm »

So I discovered something new with the "newer" control panels on WhisperWatts- at the Relay for Life I did Friday, they had a locally provided 45kW from a reputable local supplier (that never grounds their gennies, but that's a different story!). On the control panel, there was an Engine Speed switch, high speed and low speed. The tech who delivered it (I wasn't there for the drop) had switched it to low speed. When I metered the genset before use, I found 70v/150v instead of 110/220v! By switching the Engine Speed back to normal (high speed) the voltages increased to normal as well.

When the rental tech was picking it up yesterday morning, I told him about this, and he was surprised that this lowering of speed also lowered the voltage. He said he'll speak to their engineers... but first--

Has anyone encountered that same switch on a diesel generator?
Is it supposed to reduce the voltage along with the engine speed (I feel like it's supposed to be like the "Eco-throttle" on Honda EU generators?), or was that control malfunctioning on this unit?

Does it just seem like a stupid thing to have? Haha.

-Ray

Many many generators have that switch, especially the larger generators.

My understanding is that you start it off in lower speed to warm it up and after a few minutes turn it on to full speed. 

You keep the main breaker off until it is at full speed, you check the voltage at the generator panel. Then you check the voltage at your PD while the main breaker if off of course.

You do the reverse when turning the generator off for the night.

A few years ago I was at a festival where the generator was powered off due to a storm.  The stage manager was a bit over-eager and turned the generator back on, left it in low speed mode and switched on the main breaker.

We (audio) were fine because my monitor tech is smart and left our PD main breaker off until he could check the power again.

Lighting , unfortunately, had no main breaker and blew every fuse in every dimmer rack of a 120k rig.  They had a few spares and limped through the night until some one could make it to radio shack the next day.  It could of been way way worse...

Jason
« Last Edit: June 08, 2014, 09:14:44 pm by jason misterka »
Logged

Mike Sokol

  • Moderator
  • Hero Member
  • *****
  • Offline Offline
  • Posts: 3356
  • Lead instructor for the No~Shock~Zone
    • No~Shock~Zone Electrical Safety
Re: Testing Generator Voltage
« Reply #27 on: June 08, 2014, 09:23:24 pm »

So I discovered something new with the "newer" control panels on WhisperWatts- at the Relay for Life I did Friday, they had a locally provided 45kW from a reputable local supplier (that never grounds their gennies, but that's a different story!). On the control panel, there was an Engine Speed switch, high speed and low speed. The tech who delivered it (I wasn't there for the drop) had switched it to low speed. When I metered the genset before use, I found 70v/150v instead of 110/220v! By switching the Engine Speed back to normal (high speed) the voltages increased to normal as well.

Remember that a standard copper/iron AC generator needs to have a specific RPM from the motor to maintain both frequency and voltage. I'm guessing that the low speed is for warmup (as noted earlier), but not for power production. The Honda and Yamaha Inverter generators actually have an electronic inverter on the output which locks the AC frequency to 60 Hz (or 50 Hz) no matter what engine RPM. That's great for economical fuel usage since during times of low power draw the motor can be running much slower and use much less fuel. But alas, for a standard spinning-rotor generator there no such thing as eco-mode, so it has to spin at full speed to maintain 60 Hz even if it's only powering the smallest appliance or guitar amp. Since a number of digital voltmeters also read frequency, try to measure the Hz next time you find a big genny in "slo-mode" and I'm sure it will be a lot less than 60 Hz, maybe 40 or even 30 Hz. 
Logged
Mike Sokol
mike@noshockzone.org
www.NoShockZone.org

Tim Padrick

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 909
  • Indianapolis
    • T.P. Audio
Re: Testing Generator Voltage
« Reply #28 on: June 09, 2014, 12:08:30 am »

... But my viewpoint is that as soon as you distribute generator power to multiple locations (Amp racks, FOH console, Backline, etc..) there's way too much possibility that a single hot-to-ground failure on one power feed could bias every chassis on the backline to 120-volts above earth potential. And that's how musicians and singers get shocked and possibly killed.

Would that not pop the breaker?
Logged

Jonathan Johnson

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2998
  • Southwest Washington (state, not DC)
Re: Testing Generator Voltage
« Reply #29 on: June 09, 2014, 01:27:43 am »

...But my viewpoint is that as soon as you distribute generator power to multiple locations (Amp racks, FOH console, Backline, etc..) there's way too much possibility that a single hot-to-ground failure on one power feed could bias every chassis on the backline to 120-volts above earth potential. And that's how musicians and singers get shocked and possibly killed.   

Would that not pop the breaker?

Not necessarily. The scenario is a hot to earth ground fault (earth ground being the metal frame of the stage), but the generator is not grounded (but the EGC in the distro is bonded to neutral at the genny). Because there is no connection between the earth ground and generator ground, there is not a complete circuit, so the breaker doesn't trip. But once Joe Vocalist grabs the wired microphone with a shield connected to chassis ground (assuming all the gear is somehow insulated from the stage, such as with rubber casters or feet), he completes the circuit. The current flow through the human body will not be sufficient to trip the breaker, but it will be sufficient to stop the heart.
Logged
Stop confusing the issue with facts and logic!

ProSoundWeb Community

Re: Testing Generator Voltage
« Reply #29 on: June 09, 2014, 01:27:43 am »


Pages: 1 2 [3] 4 5   Go Up
 



Page created in 0.066 seconds with 24 queries.