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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => AC Power and Grounding => Topic started by: Dave Guilford on June 26, 2018, 11:14:13 AM
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Been renting small MQ15kVA generators for a few years. Got lined up at another rental co and the smallest they offer is a 25kVA. Same price too, and about 30 mins closer to their shop.
Their 25kVA has 3-phase option. When / why would I do that? What benefits do I get from 3 phase versus regular ass 1 phase.
And what about 240 vs 120. I think virtually all my gear is “universal power supply” type where it’ll take 100-250v or whatever.
Teach me.
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Been renting small MQ15kVA generators for a few years. Got lined up at another rental co and the smallest they offer is a 25kVA. Same price too, and about 30 mins closer to their shop.
Their 25kVA has 3-phase option. When / why would I do that? What benefits do I get from 3 phase versus regular ass 1 phase.
And what about 240 vs 120. I think virtually all my gear is “universal power supply” type where it’ll take 100-250v or whatever.
Teach me.
What did Guitar Center say?
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the 25kw will give you more amperage in single phase than you have now. 3 phase gives you 1/3 more amperage to use.
Basically if a generator is 3 phase the KW power is rated for 3 phase. When you set it for single phase you loose one leg of power or 1/3 of your available amps.
For example a generator rated for 25kw at 3 phase is a basically 70 amps per phase giving you 210 total amps. when you change the generator to single phase you have around 140 amps available for use. ALL of this is depends on how the generator monitors the legs for over current and voltage.
If you change your equipment to 208v I think you will be changing them back and forth for smaller shows. Leave them at 120v and get a AC distro. If you get a 3 phase distro, mark which outlets are on each phase. This helps when you can only get single phase.
I have I did not confuse you....
jd
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Great reply and thank you. The last thing you mentioned was building distro for 3phase.
But when I use it for single phase, as you mention, what happens? “When you can only get single phase power”. Does that mean 1/3 if my outlets won’t work?
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But basically the answer to “when to 3-phase” is “whenever you can”.
I’ve been renting from UR and Sunbelt and the like. They provide those ugly yellow spider boxes. Those probably don’t denote which circuits are on which legs, do you suspect?
Usually it’s california type 50a feeder
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But basically the answer to “when to 3-phase” is “whenever you can”.
I’ve been renting from UR and Sunbelt and the like. They provide those ugly yellow spider boxes. Those probably don’t denote which circuits are on which legs, do you suspect?
Usually it’s california type 50a feeder
Don't use three phase unless you have a three phase distro.
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Don't use three phase unless you have a three phase distro.
Yep, this. Unless you have the distro for it 3p is useless to you.
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the 25kw will give you more amperage in single phase than you have now. 3 phase gives you 1/3 more amperage to use.
Basically if a generator is 3 phase the KW power is rated for 3 phase. When you set it for single phase you loose one leg of power or 1/3 of your available amps.
You don't normally loose power that way on a truly switchable generator. Typically they have some multiple of 6 poles and maybe some center taps to switch around depending on the voltage and phase settings.
The important thing to do is meter your outputs to make sure you're getting what you expect based on the connected distribution. I have seen over 170V on a 120V connection to a generator. That is not counting the times a tech set the generator for 480 3 phase when we expected 120/240V single phase.
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Let's take a minute to step back and address something critical that's possibly being overlooked. My apologies if everyone knows this and is assuming as such, but I want to make certain the OP is aware of this when deciding whether to run single or three phase on the generator.
If you are renting diesel generators, ONLY in 1Ø mode are those 50A twist locks connections available. If you set the unit to 3Ø, those twist locks will NOT be functioning. So, 3Ø will not get you "more power" to the twist-locks, and "some outlets (on the spider boxes) will not be functioning" will not be the case.
The lugs (for attaching cams to) will work in either 1Ø or 3Ø. There's silk-screen graphics indicating as to which two lugs to connect to when only running 1Ø; you hit all three for 3Ø. If your rented unit has cam lugs bolted to the body (for ease of connections; often these are fed with internal cabling to the aforementioned lugs, and are usually after-market installs... not sure if Cat, MQ, etc, offer that as an option from the factory) then those cams are going to always be hot whether the generator is running 1Ø or 3Ø.
Breakers: Everything is still covered by the main breaker in the control panel. On a 25kW unit, its typically 60A. On a 45kW usually 110A. It's a three-pole breaker, but covers the system regardless of whether it's in 1Ø or 3Ø mode. So, JD was on the right track when he said that 3Ø would give you more amperage than you have now (technically a 50% increase from 120A to 180A; 120A IS a 1/3 hit from 180A but blah blah math and being pedantic ;) ) -- but again, when you are in 1Ø mode, that extra "power" for being in 3Ø mode just isn't available. This is why I mentioned the use of spider boxes- changing to 3Ø mode isn't going to free up that extra power for use with spider boxes. 1Ø is only pulling from the U & W legs (they're marked "U," "V" and "W.").
What's also important to keep in mind is that in 1Ø mode, when you're breakered at 60A (on that 25kW unit), that's covering BOTH 50A twist locks. So, even though in your mind you have 100A/220V (2-50A circuits) you are still going to be restricted by the 60A MAIN breaker. (60A per leg/220V.)
Finally, spider boxes normally come with an L6-30 30A/250V (H-H-G) as one of the circuits. Some rental shops converted those to L14-30, which can be useful for you. It's never a bad idea to ask if your rental shop has some of those converted boxes, and if they don't (and you know you'll be using them regularly) to make you one or two.
-Ray
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The important thing to do is meter your outputs to make sure you're getting what you expect based on the connected distribution. I have seen over 170V on a 120V connection to a generator. That is not counting the times a tech set the generator for 480 3 phase when we expected 120/240V single phase.
"Gosh, Tom, how does the voltage get changed?"
PICTURE TIME! (I wish I had already gotten my generator wrapped with my company logo and such, so it'd look way cooler than it does.... alas.)
1) (45kW.jpg) Here's a typical 45kW WhisperWatt.
2) (LookHere.jpg) This is the side panel you'll probably need to open.
3) (Inside.jpg) Here's what it looks like inside.
4) (ModeSelect.jpg) This is the voltage selection switch. THE ENGINE MUST BE OFF WHEN CHANGING THIS SWITCH.
5) (lugs.jpg) The graphics on the lugs, showing you which lugs to connect to based on the output you want. We have cam tails attached to the generator permanently, so I don't have to futz with these anymore. When someone has 1Ø cams/distro (a distro with 1Ø cams) I attach to my black and blue cam tails, that are wired to "U" and "W" respectively.
-Ray
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"Gosh, Tom, how does the voltage get changed?"
PICTURE TIME! (I wish I had already gotten my generator wrapped with my company logo and such, so it'd look way cooler than it does.... alas.)
1) (45kW.jpg) Here's a typical 45kW WhisperWatt.
2) (LookHere.jpg) This is the side panel you'll probably need to open.
3) (Inside.jpg) Here's what it looks like inside.
4) (ModeSelect.jpg) This is the voltage selection switch. THE ENGINE MUST BE OFF WHEN CHANGING THIS SWITCH.
5) (lugs.jpg) The graphics on the lugs, showing you which lugs to connect to based on the output you want. We have cam tails attached to the generator permanently, so I don't have to futz with these anymore. When someone has 1Ø cams/distro (a distro with 1Ø cams) I attach to my black and blue cam tails, that are wired to "U" and "W" respectively.
-Ray
The voltage fine adjustment is not pictured and that's where I find changes have been made by the previous user.
Voltage drop over 300ft of #16 orange extension cords? Turn up the voltage rather than use larger wire or moving the genset. I had one rental unit show up with the correct selection switch setting but putting out 156v on the Edison convenience outlet. A screwdriver fixed that in 15 seconds.
Next item- NEVER trust the volt meters on the genset. No horror story of my own but have heard enough about guys/gals mis-reading or blindly trusting them and not noticing 140v instead of ~120v.
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Been renting small MQ15kVA generators for a few years. Got lined up at another rental co and the smallest they offer is a 25kVA. Same price too, and about 30 mins closer to their shop.
Their 25kVA has 3-phase option. When / why would I do that? What benefits do I get from 3 phase versus regular ass 1 phase.
And what about 240 vs 120. I think virtually all my gear is “universal power supply” type where it’ll take 100-250v or whatever.
Teach me.
If you don't have a 3 phase distro and 3 phase rackpacks and 5 conductor wiring, you use single (split) phase. That's it.
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First of all, a "LIKE" to Ray.
More fuzziness in my head, re: the mode select image, it says "3 phase, 240/139V" Somebody please explain.
Thanks
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The voltage fine adjustment is not pictured and that's where I find changes have been made by the previous user.
Here's the back panel of a typical WhisperWatt. (Controls.jpg) (Why yes, the same one from before. haha.) As Tim mentioned, you can see "Voltage Regulator" at the top of the controls. The meter next to it is Hertz (frequency), so you need to look down for the "V" meter.
Here's a closer look at that Voltage Meter (VoltageMeter.jpg). Note the black knob to the left. That allows you to chose which legs you are measuring between. It's set for W-U right now, since it's in 1Ø mode. This selection knob will let you measure between the other leg if you change to 3Ø mode. To be candid, it's always in W-U since whether we're in 1Ø or 3Ø, that setting is always measuring.
Next item- NEVER trust the volt meters on the genset. No horror story of my own but have heard enough about guys/gals mis-reading or blindly trusting them and not noticing 140v instead of ~120v.
Yep.
As you adjust the Voltage Regulator at the top, you will see this "V" meter change. Best Practice would be to have someone at your spider box/distro with a meter, and they call the change, "up," "down," "bump a bit," and "perfect." This way you are allowing for any voltage drop over the cable (as opposed to metering the generator courtesy outlets) and getting the optimal voltage at your gear.
Side note: Newer generators have a "Reduced power" setting. I guess it's beneficial to the engine to start it in "low power," and then wait for it to warm up before going to "full power?" That reduced power will affect the voltage though! I had a rental unit at a show once where I was measuring about 70V leg-to-neutral. I was wondering what-the-eff was wrong with it, when I saw the "low power" setting engaged. Disengaged it, and it throttled right up to full power and voltage!
Take away: ALWAYS inspect all settings before starting the generator. :)
Bonus points: I've not touched anything on my WhisperWatt since it was used on Sunday, other than opening the panel. Can you see what is "not a best practice" that's shown in these pictures?
-Ray
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First of all, a "LIKE" to Ray.
Thanks. :)
More fuzziness in my head, re: the mode select image, it says "3 phase, 240/139V" Somebody please explain.
I know 139V is a factor somewhere (I think because it's part of the 3Ø equation?), I just can't state exactly what. That top position, though, is what we use for 3Ø operation, where it measures 120V leg to G/N and 208V leg-to-leg. (139V is 2/3 of 208V...)
I've never used it in 3Ø 480/277 mode.
-Ray
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Thanks. :)
I know 139V is a factor somewhere (I think because it's part of the 3Ø equation?), I just can't state exactly what. That top position, though, is what we use for 3Ø operation, where it measures 120V leg to G/N and 208V leg-to-leg. (139V is 2/3 of 208V...)
I've never used it in 3Ø 480/277 mode.
-Ray
If you regulate your voltage so you get 240v leg to leg, then your leg to neutral voltage will rise to 139v. This is not desirable if you are using line to neutral loads, as 139v is way above spec, but is apparently provided for motor loads that require 240v instead of 208v.
This is a good example of why metering is essential.
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ray I like your post
A little note on setting voltage. There may be a high voltage shutdown on the generator....I try and not exceed 120v at generator. If you have low voltage at distro you may need to get larger feeder cable.
When using a single phase distro on 3 phase, monitor the neutral current (amps) you will see significant amperage, do not exceed the current capability of the wire used for the neutral.
inside the generator there is usually a hidden reset button. If you do not have ac out look at the instructions on the control door/panel to know where it is.
learn how to balance power on the various legs.
My suggestion for you is to talk to your generator provider. Get some hands on instruction on the generator(s) you are using. Discuss with them what you are trying to do and they will help you plan for your power growth.
There are many safety issues with distros, commercial ac, generators, grounding, etc.
off topic but the schools for our industry do not teach enough about working with ac.
jd
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Take away: ALWAYS inspect all settings before starting the generator. :)
Bonus points: I've not touched anything on my WhisperWatt since it was used on Sunday, other than opening the panel. Can you see what is "not a best practice" that's shown in these pictures?
-Ray
Yes. The main circuit breaker is in the "on" position which means it was likely disconnected with the breaker in the same operational state.
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Yes. The main circuit breaker is in the "on" position which means it was likely disconnected with the breaker in the same operational state.
Thar be it. My team shut it down without killing the main breaker first. Best Practices is to shut off main breaker, and then let the generator run for a few additional minutes at no load for a "cool down" period.
(Don't worry, I'll fire everyone involved.)
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I have only used 35kw and 45kw units.
I remember that the 35 had 2 California connectors but I think the 45 had 3. Would the 45kw still be limited to 60a across all three?
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Any generator is limited by the mains breaker. My 45kW has a 110A/3Ø mains breaker.
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480/1.73=277
240/1.73=139
208/1.73=120
Just math and simple physics
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I love picture time, hehe. Thanks Ray, and everyone else!
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The voltage fine adjustment is not pictured and that's where I find changes have been made by the previous user.
Voltage drop over 300ft of #16 orange extension cords? Turn up the voltage rather than use larger wire or moving the genset. I had one rental unit show up with the correct selection switch setting but putting out 156v on the Edison convenience outlet. A screwdriver fixed that in 15 seconds.
Next item- NEVER trust the volt meters on the genset. No horror story of my own but have heard enough about guys/gals mis-reading or blindly trusting them and not noticing 140v instead of ~120v.
The most memorable time was 150V to the food service trucks. The cooks commented how FAST everything was cooking!
I was told by the generator company that many of the construction crews turn it up to get more zip out of their power tools.
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I have been told that if your genny frequency is not precisely 60.0 Hz, tone-wheel organs will be out of tune. True?
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I've heard it happen, digital keyboard and harmonicas were in tune, B3 not so much. Generator had no tweak available, so we ran 100' 12/3 to the neighbors, problem solved.
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I have been told that if your genny frequency is not precisely 60.0 Hz, tone-wheel organs will be out of tune. True?
Yes. They use synchronous motors.
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Yes. They use synchronous motors.
I wonder if the classic studio trick for vari-speed for a tape deck would work, a Crown DC300 and a sine wave generator.
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I wonder if the classic studio trick for vari-speed for a tape deck would work, a Crown DC300 and a sine wave generator.
Without a step-up transformer, a DC300 wouldn't come close to 120 Volt output- there must be more to "the classic studio trick".
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Tried to run a Hammond on a "construction grade 3500 Watt gen set and this is a real problem. The new "inverter type" generators probably won't have this problem. One additional problem with 3-phase, but not with any generator I know of is what is called (in my older down town area) "wild leg 3-phase". I think there is a correct technical name for this that I don't remember. When measuring between each leg and ground or neutral, two of the legs measure 120V and the remaining leg measures 240V! Three phase motors run fine on this, but if a guitar amp or some other 120V only gear gets plugged into the "wild leg", you'll have magic blue smoke!
Another caution speaking of guitar amps. I have seen the "fine" voltage adjust on generators set to almost 140V as was mentioned above. This can also destroy some 120V gear, especially vintage amps. I had this happen before we have even connected our distro and measured voltages. An anxious guitar player that wanted to hear his "find of a lifetime" vintage amp hooked himself up to the gen set's 120V outlets only to have his new prize melt-down in the first few minutes.
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Tried to run a Hammond on a "construction grade 3500 Watt gen set and this is a real problem. The new "inverter type" generators probably won't have this problem. One additional problem with 3-phase, but not with any generator I know of is what is called (in my older down town area) "wild leg 3-phase". I think there is a correct technical name for this that I don't remember. When measuring between each leg and ground or neutral, two of the legs measure 120V and the remaining leg measures 240V! Three phase motors run fine on this, but if a guitar amp or some other 120V only gear gets plugged into the "wild leg", you'll have magic blue smoke!
Another caution speaking of guitar amps. I have seen the "fine" voltage adjust on generators set to almost 140V as was mentioned above. This can also destroy some 120V gear, especially vintage amps. I had this happen before we have even connected our distro and measured voltages. An anxious guitar player that wanted to hear his "find of a lifetime" vintage amp hooked himself up to the gen set's 120V outlets only to have his new prize melt-down in the first few minutes.
https://en.wikipedia.org/wiki/High-leg_delta
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Thank you Tim! I knew that term once, but . . . Now I understand the how and why.
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I need to find a 60hz line regulator for my Hammond C3.
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I need to find a 60hz line regulator for my Hammond C3.
I don't know anything that will correct line frequency other than a full time interactive UPS.
The only other way would be a motor hooked to a generator with a VFD to tune the speed.
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I don't know anything that will correct line frequency other than a full time interactive UPS.
The only other way would be a motor hooked to a generator with a VFD to tune the speed.
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The only other way (which is a worse hack than a variable-speed motor driving a generator) is a power amplifier fed a 60Hz input. Neither the generator or the power amp “solutions” are safe or practical. The only real choice, as you have said, is a UPS, however in this case, the correct term is probably “double-conversion” or “online” rather than line interactive.
The principle that is needed is that the load is always powered from the DC to AC inverter, which generates clean, regulated and stable-frequency power. This inverter is powered by a battery, which is continuously charged by a rectifier. Any other kind of UPS where the load is not fully supplied 100% of the time by the inverter - i.e. any UPS that does any kind of load switching - will not help.
Double-conversion UPSes tend to be large and/or expensive. In casual situations (minimal inspector oversight and no great loss of revenue or reputation if the Hammond goes down), it may be possible to roll your own double-conversion UPS with a portable inverter, a deep-cycle lead-acid battery, and a large battery charger capable of sustanied 50A+ @12v current. This isn’t going to make OSHA very happy, but it’s a lot better than a VFD-driven generator or power amp driving a 120v socket.
Hammond’s don’t draw a ton of power - a 1000w inverter should have enough reserve power to drive both the console and the Leslie.
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Sounds like a solution looking for a problem to me-grid line frequency is reliable (at least in North America). Off the grid, get an inverter genny?
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Sounds like a solution looking for a problem to me-grid line frequency is reliable (at least in North America). Off the grid, get an inverter genny?
Drifting maybe further OT
Reading this I realised I had no idea at all how stable the grid frequency is (over here in the UK) but found this interesting Live monitoring site (http://gridwatch.co.uk/frequency). Looks to be about within +/- 0.4%.
The couple of spec sheets I found quickly for small double conversion UPS systems seem to spec +/- 3%. Couldn't find a spec for a Honda inverter generator, but another brand (Clarke in UK) is +/-1%.
I suppose the question is how stable do you need for a Hammond C3?
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I suppose the question is how stable do you need for a Hammond C3?
It has to stay in tune with the guitar. Jon Lord , Don Airey , Rick Wakeman , Keith Emerson and others played out door concerts with hammond B,C and A series. They were powered from jennys. I never thought about the possibility of a jenny not holding a steady 60hz. I am not concerned about the speed of my leslie 122's as there speed is for the doppler effect and not note tuning.
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I suppose the question is how stable do you need for a Hammond C3?
Since the Hammond's tone wheels are dependent on line frequency, any deviation from 60Hz (or 50Hz for those designed for 50Hz) will reduce or increase the pitch.
Reducing from 60 to 56.6 Hz drops a semi tone (half tone/half step). A semi tone has 100 cents, as little as 5-6 cents can be noticed as "out of tune" by those who are pitch sensitive, while 25 cents off sounds off to most anyone.
Assuming a "sloppy" 60 Hz, a variation of +/- 1% would be around a minor third down to a major third up.
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Being a Hammond player myself, I've heard of this gadget for decades, but never saw one in the wild. It allows a B3 to transpose the key by generating something other than 60 Hz for the tone generator motor.
https://www.organguru.com/tone-wheel-organ-transposer-system/
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Being a Hammond player myself, I've heard of this gadget for decades, but never saw one in the wild. It allows a B3 to transpose the key by generating something other than 60 Hz for the tone generator motor.
https://www.organguru.com/tone-wheel-organ-transposer-system/
Thanks for the info. I gotta get one.