Mep 002a output in amps / %rated current meter

[RWG421]

I am trying to understand the 002a capabilities, and the relationship between the %rated current meter, powerfactor and output in amps.
I understand that the unit produces; 52 amp 120 v .8 pf = 5 kw / with the %rated current meter at 80%.
Can I assume that at: 100% I get 6.24 kw.
133% = 8.29 kw

And a surge rating of 300% = 18.72 kw

If so does this mean it should carry a 69 amp single phase load running at 133% ?

Thanks for any insight on this matter,

 

[SCSG-G4]

What elevation are you running it at, and what is the nominal air temperature? They are rated by the mil specs at 8000 feet elevation and 120 degrees F. Lower elevations and temps will produce more power (amps) at the same power factor. At sea level and 80 degrees they are the equivalent of a civilian 8kw generator.

 

[ETN550]

What elevation are you running it at, and what is the nominal air temperature? They are rated by the mil specs at 8000 feet elevation and 120 degrees F. Lower elevations and temps will produce more power (amps) at the same power factor. At sea level and 80 degrees they are the equivalent of a civilian 8kw generator.

I have seen this discussion before and acknowledge that oru MEP are very conservativly rated. But does the military actually rate them more for lower elevation and temp?

The engine will produce more at lower elevation due to air density if the fuel is adjusted up.

However, the generator sections ability to overload is dependent on temperature not elevation. The civilian rating at sea level is probably the best guideline for the overall rating of the set.

If the engine is overloaded but not dangerously over fueled no harm will come, it will just drop rpm and quit. If the gen side is overloaded it can overheat and burn up.

I would focus on the generator side to determine the overload capacity and base it on the civilian spec. JMHO.

 

[RWG421]

For the sake of this discussion lets assume the best operational environment. ( sea level , 75 degrees, sunny, ect....)

 

[RWG421]

so does this mean it should carry a 69 amp single phase load running at 133% ?

Based on the assumptions I made above, is the quote correct at a .8 power or a 1.0 PF . From what I understand about power factor the limitations are the engines HP... I think?

Having the Tm state the the genset should run with the %rated current meter at 80% and the power factory being .8 are these two related? IE. If the %rated current meter is at 100% is the PF 1.0 ?

My main quest is to understand what KW i will get at 133% and at a 300% surge

Thanks All for your input

 

[ETN550]

so does this mean it should carry a 69 amp single phase load running at 133% ?

Based on the assumptions I made above, is the quote correct at a .8 power or a 1.0 PF . From what I understand about power factor the limitations are the engines HP... I think?

Having the Tm state the the genset should run with the %rated current meter at 80% and the power factory being .8 are these two related? IE. If the %rated current meter is at 100% is the PF 1.0 ?

My main quest is to understand what KW i will get at 133% and at a 300% surge

Thanks All for your input

One of the experts needs to clarify this but I'll try hoping I don't mis speak.

My 3kw 016B has the similar specs. I think what they are saying is that if you have an inductive load, such as a motor, and if that motor has a power factor of .8 then you will be at full load on the generator when the meter is at 80%.

Likewise, if you have a pure resistive load like an electric heater then your power factor is 1.0 and you are at full load when the meter is at 100%

If you have a mixture of loads, in reality, the actual PF is somewhere in the middle.

The reason for why the full load is made at 80% on the meter when using motors is because of what the motor does to the generator. AC current is like a wave as it is transmitted in the wire. It has peaks and valleys. As a resistive load (like a heater) travels the voltage peak and the current peak are coincident or ride together which gives a PF of 1.0 Inductive loads such as motors or transformers create a situation where the peak current does not occur at the peak voltage. (If I remember right the current lags the voltage) The Power, (Kw) = the voltage X the current. Therefore, the 80% max meter reading at full power and 0.8 PF is pushing the generator windings as much as 100% meter at 1.0 PF. If the gen was run at 100% meter with a motor load with .8 PF then the gen would be overloaded.

Stated another way the load meter and the PF are not directly related.
The PF is determined by the type of and combination of equipment connected to the gen. The more inductive the load is the more it is going to shift the voltage peaks from the current peaks and the lower the reading on the power meter will be to make 100% load. When hooking up heaters, light bulbs, small electronics the PF will be 1.0 and the gen will be at 100% rated load at 100% meter indication. Larger motors will usually have a PF number on their nameplate. If one was to run only a large motor as the gen load then the PF of the motor would determine where 100% load is met by the meter. The TM uses .8 PF at 80% as the guideline, but I have seen plenty of motors with .75 PF. Generally, inductive loads that have less than 1.0 PF are any devices with coils or windings in them and operate by induction such as motors or transformers.

Of course these gens can be overloaded beyond 80% at .8 or 100% at 1.0 which is where you are going with your question. I just wanted to clarify what the PF is and how it relates to the load meter and why they give us different meter limits for 1.0 and 0.8 PF.

In order to get to the maximum Amp limits you are looking for or to relate your Amps to the % load or overload you will first have to know if you have any significant motors or transformers on your load and what the PF will be. For backfeeding a house I would say you are close to 1.0 PF unless you are running an A/C unit or heat pump. For running a bunch of motors in a workshop or a 240vac pressure washer or a big air compressor the PF will need to be considered.

If the gen was to only power inductive loads, like a big motor, and these loads were always the same every time, then large capacitors can be added between the generator and the load to make the PF closer to 1.0. Electric Utility companys do this on their poles where their transformers feed customers with a lot of motors or the like.

Back to your main question: (for single phase, three phase is different)

If your loads create a PF of 1.0 and 52A is considered 100% load, then Kw = 52 x 120vac = 6240w or 6.24Kw

133% = 52 x 1.33 = 69A 69A x 120vac = 8280w or 8.3Kw

If your loads create a PF of 0.8 then 100% load is 52A x 0.8 = 41.6A and Kw = 41.6 x 120vac = 4992w or 5Kw (the official rating)

133% = 41.6A x 1.33 = 55.3A 55.3A x 120vac = 6636w or 6.6Kw.

So for 133%, depending on the PF you would be between 6.6Kw and 8.3Kw

Similar calculation for 300%. Edit: Something else I just thought of. In 120vac single phase mode you will probably exceed the breaker capacity before you reach 300%. Check your TM for the breaker rating and multiply it by 3.00. I bet it is less than the amps required to make the 300% which would be 52 x 3 = 156A at 1.0 PF

 

[Isaac-1]

The problem is any answer you get on load capacity is going to be an over simplificaiton as in the real world the only way to know is to push things to the failure point. In this case failure can be caused by overheating of the generator end wiring causing failure of the insulation, the thing is this insulation can be damaged through age and long term abuse, slight over heating, etc. so you not only have the unknown point at which instant failure may occur, but also a point that will slowly degrade the insulation. Of course alternatively failure may come from overloading the driver end with something breaking in the engine.

 

[ETN550]

The problem is any answer you get on load capacity is going to be an over simplificaiton as in the real world the only way to know is to push things to the failure point. In this case failure can be caused by overheating of the generator end wiring causing failure of the insulation, the thing is this insulation can be damaged through age and long term abuse, slight over heating, etc. so you not only have the unknown point at which instant failure may occur, but also a point that will slowly degrade the insulation. Of course alternatively failure may come from overloading the driver end with something breaking in the engine.

Isaac,

You make a good point about the aging of the winding insulation. This makes a good case for load testing at the rated point for several hours in typical conditions to prove out the machine. Then, from there, overloading is at ones own risk.

The driver will not be damaged as long as the max fuel is set to spec and the injection pump timing is to spec and the fuel injectors are in good shape. It does not really matter if the engine is worn out or not. As long as no more than design fuel rate is put to it and the injection is good, and the air temp is less then spec, the air shroud is closed, and fan inlet not blocked, then the worst that will happen is that the driver will bog down, loose speed, and quit.

The generator end, as you mention is a whole nother matter.