I'm starting to do a number of outdoor events which require a lot of generator power and sometimes clients have a lot of questions about generators that I can't answer. Like can all equipment be run on 3 phase power? how many subsequent transformers are needed, if any? I'm very new to running strictly of generator power.
Experience running off diesel generators
- Thread starter Kevin Spencer
- Start date
Re: Experience running off diesel generators
What is your normal Power Distro set-up? The smaller Gen Sets are switchable from single to three phase power; not sure on the larger units.
I don't need much power and I request a 15kW to 25kW gen set and use my 120/240v 50a Distro uses the Cali plug. Most of the time when the Generator is provided for me, the Rental company also includes the spider/break out box with appropriate power cable.
Also make sure the request indicates that a "whisper" or "quiet" models is required, the gen rental house has "construction" gens as well and they are LOUD!
What is your normal Power Distro set-up? The smaller Gen Sets are switchable from single to three phase power; not sure on the larger units.
I don't need much power and I request a 15kW to 25kW gen set and use my 120/240v 50a Distro uses the Cali plug. Most of the time when the Generator is provided for me, the Rental company also includes the spider/break out box with appropriate power cable.
Also make sure the request indicates that a "whisper" or "quiet" models is required, the gen rental house has "construction" gens as well and they are LOUD!
Re: Experience running off diesel generators
Actually, the best solution is to sit down with your local rental house, tell them what you need to do, and let them tell you what you will need. If you are clear up front about it being for entertainment use, and the number and amperage of the circuits you need, you should get a good answer.
Actually, the best solution is to sit down with your local rental house, tell them what you need to do, and let them tell you what you will need. If you are clear up front about it being for entertainment use, and the number and amperage of the circuits you need, you should get a good answer.
Re: Experience running off diesel generators
We routinely use large generators in the 100kW up to 200kW range, and once, a 350kW unit (the latter being installed in a 45ft semi trailer) with no issues, but I know what I'm looking for and what to watch out for and have regular discussions about the topic with the genset guys (like the time a 125kW genset showed up with a totally digital control center. They sent it out with no instructions on how to set and store the necessary voltage requirements in the memory of the digital control center. Monday morning, we had a roundtable on that rascal!). Sometimes, we use 2 100kW generators and there are things to do under these circumstances. Not being a certified electrician, I'm not comfortable discussing this on a forum such as this. For the safety and well-being of all personel and gear involved, you are better off having and paying an electrician to help and advise you along the way.
Good luck,
Geri O
You definitely want to consult with a local electrician that can help the discussion between you and the generator company. He can help decipher the language that goes on with those discussions.
We routinely use large generators in the 100kW up to 200kW range, and once, a 350kW unit (the latter being installed in a 45ft semi trailer) with no issues, but I know what I'm looking for and what to watch out for and have regular discussions about the topic with the genset guys (like the time a 125kW genset showed up with a totally digital control center. They sent it out with no instructions on how to set and store the necessary voltage requirements in the memory of the digital control center. Monday morning, we had a roundtable on that rascal!). Sometimes, we use 2 100kW generators and there are things to do under these circumstances. Not being a certified electrician, I'm not comfortable discussing this on a forum such as this. For the safety and well-being of all personel and gear involved, you are better off having and paying an electrician to help and advise you along the way.
Good luck,
Geri O
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Re: Experience running off diesel generators
Sizing a generator is not hard. They are equivalent to what you would need from house power. If you have a 3 phase distro, or split phase distro, you will simply set the generator to whatever you need. Please note that you cannot simultaneously run 120/240 and 120/208 on the same genset. You have to pick one and stick with it.
I own my own generator since I kept getting promoters who would save money by getting the smallest, weakest unit possible for shows. Now, they either rent my generator or I won't do the show. It is also advisable to get a generator sized 140% of your system load or you will get "surging", where the generators engine can't keep up with the dynamic load and starts to rock back and forth to the music...which is very bad.
So, I have a distro that has a 3phase 100A main breaker. Coincidentally, that matches a 75KVA generator (which also has a 100A main breaker) and that works perfectly.
At one time in the past, I tried to connect a huge amount of amps and equipment to a tiny 35kva generator, and I stalled it. It is always better to oversize your unit.
Sizing a generator is not hard. They are equivalent to what you would need from house power. If you have a 3 phase distro, or split phase distro, you will simply set the generator to whatever you need. Please note that you cannot simultaneously run 120/240 and 120/208 on the same genset. You have to pick one and stick with it.
I own my own generator since I kept getting promoters who would save money by getting the smallest, weakest unit possible for shows. Now, they either rent my generator or I won't do the show. It is also advisable to get a generator sized 140% of your system load or you will get "surging", where the generators engine can't keep up with the dynamic load and starts to rock back and forth to the music...which is very bad.
So, I have a distro that has a 3phase 100A main breaker. Coincidentally, that matches a 75KVA generator (which also has a 100A main breaker) and that works perfectly.
At one time in the past, I tried to connect a huge amount of amps and equipment to a tiny 35kva generator, and I stalled it. It is always better to oversize your unit.
Craig Hauber
Sophomore
Re: Experience running off diesel generators
Are you sure you have your numbers right? A 250kW is a tow-behind weighing around 10,000lbs and the tractor-trailer sized ones I've been hooked to are in the 1.5 to 1.8 MW range. (yes, most of the time way-overkill but some clients just get taken)
http://www.cat.com/cda/files/3732062/7/Cat XQ200 Rental Power Module LEHX0011-00.pdf
http://www.cat.com/cda/files/4411176/7/XQ2000.pdf
Are you sure you have your numbers right? A 250kW is a tow-behind weighing around 10,000lbs and the tractor-trailer sized ones I've been hooked to are in the 1.5 to 1.8 MW range. (yes, most of the time way-overkill but some clients just get taken)
http://www.cat.com/cda/files/3732062/7/Cat XQ200 Rental Power Module LEHX0011-00.pdf
http://www.cat.com/cda/files/4411176/7/XQ2000.pdf
Re: Experience running off diesel generators
Always oversize as Tim said. Also meter the power before you plug in.
Always oversize as Tim said. Also meter the power before you plug in.
Re: Experience running off diesel generators
Most DEF!
I was plugging into the Genset one time that was being provided by the Tent/Lighting Co for a wedding event. They called me and told me to fire up the genset once I arrived (they did set-up the day before) and everything is good to go. I went and started the Gen set and within 20-30 second later all the lights went "poof". I grabbed the meter and tested it, their PDU was pushing 250+ volts on an Edison outlet and the same on the Lugs. I shut it down and called them, they came out and couldn’t get the voltage selector switch to move out of the 480; they ended up swapping gen set and replacing 30 Par38 bulbs.
Most DEF!
I was plugging into the Genset one time that was being provided by the Tent/Lighting Co for a wedding event. They called me and told me to fire up the genset once I arrived (they did set-up the day before) and everything is good to go. I went and started the Gen set and within 20-30 second later all the lights went "poof". I grabbed the meter and tested it, their PDU was pushing 250+ volts on an Edison outlet and the same on the Lugs. I shut it down and called them, they came out and couldn’t get the voltage selector switch to move out of the 480; they ended up swapping gen set and replacing 30 Par38 bulbs.
Re: Experience running off diesel generators
Remember that when you plug into a regular wall outlet, you CAN get more power than the breaker is rated for peak demands. Power amps do not draw a linear load, and will occasionally draw far more than their rated power. It's not a big deal, as the burst draws are fairly short, so total average current won't blow a breaker. However, on a generator, if you match the size of the generator to the size of breaker you usually use, there isn't going to be any overhead left available when needed. Bigger is ALWAYS better.
And be cautious about trusting any electrician working on the generator. I'm not a certified electrician, but I've seen 'certified' electricians do some pretty dumb stuff. Verify and measure EVERYTHING before connecting your gear. A good electrician should not be offended if you look in the panel to confirm their connections.
Remember that when you plug into a regular wall outlet, you CAN get more power than the breaker is rated for peak demands. Power amps do not draw a linear load, and will occasionally draw far more than their rated power. It's not a big deal, as the burst draws are fairly short, so total average current won't blow a breaker. However, on a generator, if you match the size of the generator to the size of breaker you usually use, there isn't going to be any overhead left available when needed. Bigger is ALWAYS better.
And be cautious about trusting any electrician working on the generator. I'm not a certified electrician, but I've seen 'certified' electricians do some pretty dumb stuff. Verify and measure EVERYTHING before connecting your gear. A good electrician should not be offended if you look in the panel to confirm their connections.
Re: Experience running off diesel generators
Definitely check if it is someone elses work. I have actually had an "expert" DISASSEMBLE part of my generator on a dry power rental because he thought that bypassing all of the safeties gave you "more power." If someone mixes up the hots and the neutral, best case is that all your equipment catches fire, worst case is that you die.
Definitely check if it is someone elses work. I have actually had an "expert" DISASSEMBLE part of my generator on a dry power rental because he thought that bypassing all of the safeties gave you "more power." If someone mixes up the hots and the neutral, best case is that all your equipment catches fire, worst case is that you die.
Re: Experience running off diesel generators
It is also important to understand that the generators only delivers up to its rated maximum/peak power at any time.
This means, for arguments sake, that a generator that delivers a maximum of 1kW can only start a motor rated up to 100W if the starting power is 10 times the running power for that motor!
This is important to remember for anything that have a high inrush current when cold starting (lamp, motors, amps, etc...)
It is also important to understand that the generators only delivers up to its rated maximum/peak power at any time.
This means, for arguments sake, that a generator that delivers a maximum of 1kW can only start a motor rated up to 100W if the starting power is 10 times the running power for that motor!
This is important to remember for anything that have a high inrush current when cold starting (lamp, motors, amps, etc...)
Re: Experience running off diesel generators
Generators are not sized in watts, they are sized in volt-amps. This means that you need to take the power factor of your equipment into account when sizing the generator. One rule of thumb is to use a power factor of between 0.6 and 0.8 if the actual power factor is unknown.
All the diesel generators I've ever run across are 3-phase machines, although many can also be configured for single-phase operation. You want to balance your loads as evenly as possible across the 3 phases (this is good practice in any system).
The generator has a nonzero ramp time, which means that quickly adding or subtracting large loads may stall the generator or result in overvoltage events. Better generators have better voltage regulation, but it still isn't typically as good as you'd get from shore power.
Generators are not sized in watts, they are sized in volt-amps. This means that you need to take the power factor of your equipment into account when sizing the generator. One rule of thumb is to use a power factor of between 0.6 and 0.8 if the actual power factor is unknown.
All the diesel generators I've ever run across are 3-phase machines, although many can also be configured for single-phase operation. You want to balance your loads as evenly as possible across the 3 phases (this is good practice in any system).
The generator has a nonzero ramp time, which means that quickly adding or subtracting large loads may stall the generator or result in overvoltage events. Better generators have better voltage regulation, but it still isn't typically as good as you'd get from shore power.
Re: Experience running off diesel generators
Yes, Craig, I did mis-type there. It should have been 350kW, but it was inside a 45ft trailer. And yes, it did look like overkill. There was a lot of sound-deadening material and there was still a lot of space inside. Unfortunately, you had to climb inside the trailer to crank the generator and BOY, was it loud. After the first time, I used ear plugs when I had to crank it (we had it several times, including a 5-day festival). But it was very quiet.
We had spec'ed a 250kW, but this is what was available. The particular promoter, for some reason, was infatuated with this machine (hanging banners on the side of the trailer was probably a motivating factor) and kept getting it for his outdoor events.
We saw this machine for a couple of summers, then who knows, it found another home.
Geri O
Yes, Craig, I did mis-type there. It should have been 350kW, but it was inside a 45ft trailer. And yes, it did look like overkill. There was a lot of sound-deadening material and there was still a lot of space inside. Unfortunately, you had to climb inside the trailer to crank the generator and BOY, was it loud. After the first time, I used ear plugs when I had to crank it (we had it several times, including a 5-day festival). But it was very quiet.
We had spec'ed a 250kW, but this is what was available. The particular promoter, for some reason, was infatuated with this machine (hanging banners on the side of the trailer was probably a motivating factor) and kept getting it for his outdoor events.
We saw this machine for a couple of summers, then who knows, it found another home.
Geri O
Re: Experience running off diesel generators
So before I say anything, I just want to start off by saying that I work for an industrial generator company designing generator and motor control systems. Generators are in fact rated in watts and the power factor is one of two definite values. When you wire a 12 lead generator end in what they call a zigzag connection, you get single phase low voltage which of course is the usual 120/240 and the generator will always have a power factor of one when wired this way, but when you change from that to a low Y connection, which is 120/208 volts, your power factor drops to 0.8. And for those who don't quite understand power factor, think about it like this. When you use a purely resistive load on a three phase generator, say 100kw, then you can only really use 80kw of power where as if you have a power factor of 1.0, then you can use all the power that the machine is rated for, but now its time to throw a curve ball. When you wire a 12 lead generator end in a zigzag formation, creating single phase, you have to de-rate the power of the machine by one third, where as if you have a four lead generator end that is strictly single phase, then you can use all the power that the end is rated for. But if you just so happen to own an old gen-set that has four leads coming out of the generator end, don't always be so sure that it is single phase. Usually the four leads are the two leads from the inductive coils in the stater so that when you connect the two inductors in a series fashion, each end is a hot leg, and you center tap them for your neutral, but some machines can be found to be four lead and wired strictly three phase low voltage. This is mostly seen in older generator sets such as those made by Onan. Also, I must argue about how generators can be loaded. Any professional generator is rated for 80% block load, and that is usually being generous. When I load bank generators, I always do a 100% block load test because you need to imagine what a commercial building could do to it. Though any building with a large load has many automatic transfer switches to slowly add load to a generator, some older buildings do not and I often find generators that are undersized for the application. So in short, any real generator (15 ish Kw) and above should take 100% block load without dropping below 58 cycles. For anybody that has a question about a generator, feel free to email me. Generators are seriously some of the most basic machines, there theory of operation has not changed since the 50's. Its a motor driving an alternator that produces power by means of creating a rotating electromagnet.
So before I say anything, I just want to start off by saying that I work for an industrial generator company designing generator and motor control systems. Generators are in fact rated in watts and the power factor is one of two definite values. When you wire a 12 lead generator end in what they call a zigzag connection, you get single phase low voltage which of course is the usual 120/240 and the generator will always have a power factor of one when wired this way, but when you change from that to a low Y connection, which is 120/208 volts, your power factor drops to 0.8. And for those who don't quite understand power factor, think about it like this. When you use a purely resistive load on a three phase generator, say 100kw, then you can only really use 80kw of power where as if you have a power factor of 1.0, then you can use all the power that the machine is rated for, but now its time to throw a curve ball. When you wire a 12 lead generator end in a zigzag formation, creating single phase, you have to de-rate the power of the machine by one third, where as if you have a four lead generator end that is strictly single phase, then you can use all the power that the end is rated for. But if you just so happen to own an old gen-set that has four leads coming out of the generator end, don't always be so sure that it is single phase. Usually the four leads are the two leads from the inductive coils in the stater so that when you connect the two inductors in a series fashion, each end is a hot leg, and you center tap them for your neutral, but some machines can be found to be four lead and wired strictly three phase low voltage. This is mostly seen in older generator sets such as those made by Onan. Also, I must argue about how generators can be loaded. Any professional generator is rated for 80% block load, and that is usually being generous. When I load bank generators, I always do a 100% block load test because you need to imagine what a commercial building could do to it. Though any building with a large load has many automatic transfer switches to slowly add load to a generator, some older buildings do not and I often find generators that are undersized for the application. So in short, any real generator (15 ish Kw) and above should take 100% block load without dropping below 58 cycles. For anybody that has a question about a generator, feel free to email me. Generators are seriously some of the most basic machines, there theory of operation has not changed since the 50's. Its a motor driving an alternator that produces power by means of creating a rotating electromagnet.
Silas Pradetto
Graduate Student
Adrian, wanna add some info about how generators regulate voltage?
Sent from my XT907 2
Re: Experience running off diesel generators
kVA x pf = kW. The generator windings do not produce watts, they produce a current at a voltage (VA) at a specific phase angle relative to a reference. Ratings in kW may be provided as a convenience, but they always assume a power factor (typically 0.8) that may or may not reflect the actual load. An example of where the actual pf may be lower is with large banks of cheap SMPS units (this includes certain lighting loads). In such cases, it is more appropriate to use the kVA rating vs. the kW rating (both should be provided). For the entertainment world, this means that large intelligent/LED lighting rigs may require larger generators than you might initially expect.
Derating by 1/3 for single-phase operation makes sense, as you end up only using 2 of the three phases from the generator (with some transformer trickery to shift one of the phases by 30 degrees so that the 2 hot legs are 180 degrees out of phase vs. 120). Note that this is really 2-phase power, not the single-phase center tap that is typically seen in utility feeds.
kVA x pf = kW. The generator windings do not produce watts, they produce a current at a voltage (VA) at a specific phase angle relative to a reference. Ratings in kW may be provided as a convenience, but they always assume a power factor (typically 0.8) that may or may not reflect the actual load. An example of where the actual pf may be lower is with large banks of cheap SMPS units (this includes certain lighting loads). In such cases, it is more appropriate to use the kVA rating vs. the kW rating (both should be provided). For the entertainment world, this means that large intelligent/LED lighting rigs may require larger generators than you might initially expect.
Derating by 1/3 for single-phase operation makes sense, as you end up only using 2 of the three phases from the generator (with some transformer trickery to shift one of the phases by 30 degrees so that the 2 hot legs are 180 degrees out of phase vs. 120). Note that this is really 2-phase power, not the single-phase center tap that is typically seen in utility feeds.
Craig Hauber
Sophomore
Re: Experience running off diesel generators
sounds like fun!
I'm fascinated with industrial engines and getting to climb around on a 18cyl cummins with turbos bigger than my car's entire block was really interesting. (Apparently that particular engine model was also used in locomotives and that's another fascination of mine.)
sounds like fun!
I'm fascinated with industrial engines and getting to climb around on a 18cyl cummins with turbos bigger than my car's entire block was really interesting. (Apparently that particular engine model was also used in locomotives and that's another fascination of mine.)
Re: Experience running off diesel generators
This looks like a great place to drop this link I stumbled into while looking at a DI offered by a fellow forum person.
Light Plants
This looks like a great place to drop this link I stumbled into while looking at a DI offered by a fellow forum person.
Light Plants