Building a 30Kw generator
Registered User
Joined: Nov 2005
Posts: 374
Likes: 2
As an electrician, instructor and inspector, I thought I would offer a couple thoughts.
At 30,000 watts, that's equivalent to approximately a 130 amp, 230 volt, single phase service. Of course, that's assuming that is a viable continuous duty rating. That may be a peak rating, which won't yield that continuously. Either way, that's near a small commercial-sized generator. But, you're paying for the fuel to run it, so that's entirely your prerogative. You may, however, want to consider utilizing nearly half of that. Either way, you'll need overload and short circuit protection for the generator. While overload usually leads to voltage and current drops as the saturated windings will not put out any more power after peak load, excessive heat is the culprit. Short circuiting will imminently destroy the generator windings.
Most importantly- utilize some way to disconnect street power from your service, whether it be an automatic transfer device, a manual feeder transfer switch, or a group of branch circuit transfer switches. Turning off your service is never an acceptable method. Your local lineman will be knocking at your door, and/or may cut your street power should they find it was you that forgot and accidently back-fed the local grid. Yes, you can energize the primary side of the outdoor transformers enough to hurt someone.
Do you know what RPM the input shaft of the generator requires to maintain 60Hz? Most often, generators are set to run about 63Hz at no-load, or 60Hz at 40% load. As engine load increases (due to generator output ampacity), engine RPM will decrease (causing output power frequency degradation) unless you have either automatic idle circuitry to increase/decrease the engine's rpm in response to load conditions, or at minimum a mechanical means. AC power frequency is critical to non-lineal loads, which is the majority of what we use in our homes.
If you already know this stuff, then please pardon my post. Good luck and have fun!
At 30,000 watts, that's equivalent to approximately a 130 amp, 230 volt, single phase service. Of course, that's assuming that is a viable continuous duty rating. That may be a peak rating, which won't yield that continuously. Either way, that's near a small commercial-sized generator. But, you're paying for the fuel to run it, so that's entirely your prerogative. You may, however, want to consider utilizing nearly half of that. Either way, you'll need overload and short circuit protection for the generator. While overload usually leads to voltage and current drops as the saturated windings will not put out any more power after peak load, excessive heat is the culprit. Short circuiting will imminently destroy the generator windings.
Most importantly- utilize some way to disconnect street power from your service, whether it be an automatic transfer device, a manual feeder transfer switch, or a group of branch circuit transfer switches. Turning off your service is never an acceptable method. Your local lineman will be knocking at your door, and/or may cut your street power should they find it was you that forgot and accidently back-fed the local grid. Yes, you can energize the primary side of the outdoor transformers enough to hurt someone.
Do you know what RPM the input shaft of the generator requires to maintain 60Hz? Most often, generators are set to run about 63Hz at no-load, or 60Hz at 40% load. As engine load increases (due to generator output ampacity), engine RPM will decrease (causing output power frequency degradation) unless you have either automatic idle circuitry to increase/decrease the engine's rpm in response to load conditions, or at minimum a mechanical means. AC power frequency is critical to non-lineal loads, which is the majority of what we use in our homes.
If you already know this stuff, then please pardon my post. Good luck and have fun!
Registered User
Joined: Nov 2001
Posts: 4,199
Likes: 1
From: Branchville, Alabama
As an electrician, instructor and inspector, I thought I would offer a couple thoughts.
At 30,000 watts, that's equivalent to approximately a 130 amp, 230 volt, single phase service. Of course, that's assuming that is a viable continuous duty rating. That may be a peak rating, which won't yield that continuously. Either way, that's near a small commercial-sized generator. But, you're paying for the fuel to run it, so that's entirely your prerogative. You may, however, want to consider utilizing nearly half of that. Either way, you'll need overload and short circuit protection for the generator. While overload usually leads to voltage and current drops as the saturated windings will not put out any more power after peak load, excessive heat is the culprit. Short circuiting will imminently destroy the generator windings.
Most importantly- utilize some way to disconnect street power from your service, whether it be an automatic transfer device, a manual feeder transfer switch, or a group of branch circuit transfer switches. Turning off your service is never an acceptable method. Your local lineman will be knocking at your door, and/or may cut your street power should they find it was you that forgot and accidently back-fed the local grid. Yes, you can energize the primary side of the outdoor transformers enough to hurt someone.
Do you know what RPM the input shaft of the generator requires to maintain 60Hz? Most often, generators are set to run about 63Hz at no-load, or 60Hz at 40% load. As engine load increases (due to generator output ampacity), engine RPM will decrease (causing output power frequency degradation) unless you have either automatic idle circuitry to increase/decrease the engine's rpm in response to load conditions, or at minimum a mechanical means. AC power frequency is critical to non-lineal loads, which is the majority of what we use in our homes.
If you already know this stuff, then please pardon my post. Good luck and have fun!
At 30,000 watts, that's equivalent to approximately a 130 amp, 230 volt, single phase service. Of course, that's assuming that is a viable continuous duty rating. That may be a peak rating, which won't yield that continuously. Either way, that's near a small commercial-sized generator. But, you're paying for the fuel to run it, so that's entirely your prerogative. You may, however, want to consider utilizing nearly half of that. Either way, you'll need overload and short circuit protection for the generator. While overload usually leads to voltage and current drops as the saturated windings will not put out any more power after peak load, excessive heat is the culprit. Short circuiting will imminently destroy the generator windings.
Most importantly- utilize some way to disconnect street power from your service, whether it be an automatic transfer device, a manual feeder transfer switch, or a group of branch circuit transfer switches. Turning off your service is never an acceptable method. Your local lineman will be knocking at your door, and/or may cut your street power should they find it was you that forgot and accidently back-fed the local grid. Yes, you can energize the primary side of the outdoor transformers enough to hurt someone.
Do you know what RPM the input shaft of the generator requires to maintain 60Hz? Most often, generators are set to run about 63Hz at no-load, or 60Hz at 40% load. As engine load increases (due to generator output ampacity), engine RPM will decrease (causing output power frequency degradation) unless you have either automatic idle circuitry to increase/decrease the engine's rpm in response to load conditions, or at minimum a mechanical means. AC power frequency is critical to non-lineal loads, which is the majority of what we use in our homes.
If you already know this stuff, then please pardon my post. Good luck and have fun!
A four pole generator end, dedicated 110/220 will reach 60 cycle at 1800 rpm. Any generator sizing is dependant on what the use is. In my case I will be running my small shop from it, the largest load is the heli-arc with a 60 amp breaker. An efficient diesel running 20 or 30 amps will use near 1/2 gallon per hour in normal use and 1 gallon per hour at max use.
For comparison my Honda 3000is will use 1/3 gallon of gas for 10 amps average use and near 1/2 gallon per hour powering 14,000 btu air all day. The unit produces max 23 amps and is about as efficient as a commercial built generator will get.
There are a number of forums out there for practical knowledge on building these units. A well governed diesel will pick up a couple of cycles at no load but stabilize really well under load with little governor droop. Diesel is really the only way to go with a mid powered generator set.
Thread Starter
Registered User
Joined: Oct 2002
Posts: 476
Likes: 33
Registered User
Joined: Nov 2001
Posts: 4,199
Likes: 1
From: Branchville, Alabama
It is a couple of years since I was digging for info on home built generators so do not currently have links but I can help with google. Try "generator end" "generator head" "build generatoor" "solar generator" along those lines and be prepared to go through hundreds of google pages. Half of the hits will be electronic generators for computers.
Rpm costs fuel and noise. V belts cost fuel. You have single bearing generators, dual bearing generators, brushless, etc. Generally single bearing generators bolt directly to the bell adaptor of the engine in SAE sizes and require an SAE flywheel. This is the direction that I went. Dual bearing generators are usually belt or shaft driven. Some companies produce a two bearing head that also has the sae adaptor and can use a looser drive system such as the thermo king compressor uses. If you have to use belts, use flat belts.
there are governor systems out there, belt driven that can do a pretty good job and you need to figure what kind of governor the engine has now. There are many different types and I have no idea what yours has. An example, an old detroit has low rpm governor and high idle governor and all in the middle is throttle controlled. The cat engines have a governor where you set the throttle and it will govern at that point. On the road with the old cat engines you could pull the throttle cable up to set the speed and it would hold 55 all day long, sort of an early cruise control.
Go through the Marathon generator information and they have a good SAE bell and flywheel dimention chart. Pheonix in Nebraska has some pretty good sae adaptors. They have sae bells that adapt from a chevy pattern.
On my engine it has a #6 bell adaptor which is too small, Europe uses the #6 quite a bit but American companies start with#5. So I am using an adaptor from Pheonix to adapt from #6 to #5 and then machining the flywheel for the sae standard. The deapth is all wrong so am having an adaptor made to extend the drive plate deeper.
If you elect to go with belt drive you can get from ebay china generators that will fit the bill much cheaper, 5 or 6 hundred. I am using a single bearing end that has the regulator and is brushless. Cost $2200 for the unit. It is 21 kw constant run and 30 to 35 surge (peak). I wanted the well regulated clean power for powering electronic systems. I am using solar and batteries and inverter of a full off mains system.
The engine I am using is a thermo king unit which is an Isuzu 2.2 direct injection with a built in #6 bell adaptor. I am setting it up in the original housing on the trailer so that it will look like an old freight box reefer.
Rpm costs fuel and noise. V belts cost fuel. You have single bearing generators, dual bearing generators, brushless, etc. Generally single bearing generators bolt directly to the bell adaptor of the engine in SAE sizes and require an SAE flywheel. This is the direction that I went. Dual bearing generators are usually belt or shaft driven. Some companies produce a two bearing head that also has the sae adaptor and can use a looser drive system such as the thermo king compressor uses. If you have to use belts, use flat belts.
there are governor systems out there, belt driven that can do a pretty good job and you need to figure what kind of governor the engine has now. There are many different types and I have no idea what yours has. An example, an old detroit has low rpm governor and high idle governor and all in the middle is throttle controlled. The cat engines have a governor where you set the throttle and it will govern at that point. On the road with the old cat engines you could pull the throttle cable up to set the speed and it would hold 55 all day long, sort of an early cruise control.
Go through the Marathon generator information and they have a good SAE bell and flywheel dimention chart. Pheonix in Nebraska has some pretty good sae adaptors. They have sae bells that adapt from a chevy pattern.
On my engine it has a #6 bell adaptor which is too small, Europe uses the #6 quite a bit but American companies start with#5. So I am using an adaptor from Pheonix to adapt from #6 to #5 and then machining the flywheel for the sae standard. The deapth is all wrong so am having an adaptor made to extend the drive plate deeper.
If you elect to go with belt drive you can get from ebay china generators that will fit the bill much cheaper, 5 or 6 hundred. I am using a single bearing end that has the regulator and is brushless. Cost $2200 for the unit. It is 21 kw constant run and 30 to 35 surge (peak). I wanted the well regulated clean power for powering electronic systems. I am using solar and batteries and inverter of a full off mains system.
The engine I am using is a thermo king unit which is an Isuzu 2.2 direct injection with a built in #6 bell adaptor. I am setting it up in the original housing on the trailer so that it will look like an old freight box reefer.
Registered User
Joined: Jul 2006
Posts: 338
Likes: 0
You can get a chinese made Gen End on Fleabay for $300 or slightly more. They are called ST gen heads. If I were doing this project I would probably use two automotive serpentine pulleys and a serpentine belt. It's most efficient belt system. These pulleys can also be made by machinists if you have the coin. Probably going to need a bolt on governor and you can find those at surplus shops (google is your friend). There are alot of forums to help assist jsut google diesel generator forum and see which one suits you best.
Administrator
Joined: Nov 2004
Posts: 4,084
Likes: 233
From: Southern California
Thread
Thread Starter
Forum
Replies
Last Post
TWX
1st Gen. Ram - All Topics
22
Jul 1, 2012 10:24 AM
