Kenny0
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I have a MEP 802 generator and have five drill presses and five Bench grinders hooked up to it. All drill presses are identical and when checked with a kill a Watt meter they each draw 350 W of power. All the bench grinders are identical and when checked with a kill a Watt meter to each draw 215 W of power. The total wattage of the combined load is 2825 W. These are all 120 V units and hooked up to the generator so that the total load is balanced fairly good. I can't get all the units running at the same time without the generator kicking off. This is supposed to be a 5000 W generator, what the heck is going on?
Is this an extreme case? Yes, but the same thing affects any generator to some degree or other. It will affect a 100 W micro generator all the way up to a multi-megawatt power plant. Some of you already know what's going on here and what the problem is, this post is for those who do not. Could this setup run with this generator successfully? Yes, but I think that should be done in another post. If there enough interest in part 2, let me know and I will make one. Hopefully this post will help you understand why and how to prevent it. Everything in this post might not be technically 100% accurate, but I think it is perfect enough for this post.
There are several things going on with this scenario, but first we'll start off with some electrical terms that are involved here. I will list them and explain them the way it makes sense to me.
Volts – I think of this as pressure, such as pressure in a water line or an air line
Current – I think this as volume, bigger wire or bigger pipe equals larger volume
Amps – this is a measurement of current
Motor Idling – has nothing to do with RPM, it is a motor that is running but not doing any work
Power Factor – I think of this as the efficiency, low power factor low efficiency, high power factor high-efficiency. Best number here is 1.0
Potential Power – this is power that is produced but not used. I like to think of this as an air tank that has a leak. The bigger the leak the bigger the loss, the leak does not power anything but took power to produce it in the first place and continues taking power to keep the pressure in the tank high enough to do its intended work.
Watts – this is a measurement of power used, is not a measurement of power produced. This is what the utility companies use to know how much to charge you each month.
VA or volt amps – this is volts times amps. This can give an indication on power factor if you know the watts of the load. 100 W load at 1000 VA would be a very poor or low power factor 0.1. 800 W load at 1000 VA would be a good power factor 0.8. 1000 W load at 1000 VA would be a perfect power factor I.0. This would only be attainable with a resistive load.
To solve this problem we do not yet have enough information. Let's look at more information. Both motors are induction motors. First let's look at the drill press. The nameplate ratings are115 V - 9.8 full load amps. The actual readings with the motor sitting at idle, 123 V – 9.62 A – 350 W – 1190 VA – 0.3 power factor. This motor sitting at idle is drawing almost the same amount of amps as the nameplate rating at full load but is doing no work, and is only using 350 W of power, which is the power required to keep the motor running at its rated speed. So we are drawing 9.62 A from the generator to power 350 W, not very good. But what is happening to that excess power that the generator is outputting? That power would be what's called potential power, that is power produced but not used. But where does that power go, it has to go somewhere? Potential power gets dissipated as heat. As this motor gets put under more load, the watts will go up the power factor will go up and the amps will stay near the same and the generator will be producing less potential power and thus less heat. This motor is a three-quarter horse motor and should have a power factor rating of about 0.8, when I checked the power factor at maximum load I came up with 0.78, but I cannot say that that would be an accurate reading because I could not hold the full load steady enough and long enough to get an accurate reading. Same thing with the watts, it should be reading about 952 watts. I was going to list the results of the bench grinder, but the results were similar and would be redundant. In summary, the complete load of this set up is 2825 W which it seems the generator can handle without a problem, but the total load from the generator in amps is 75.35 at 120 V and that is beyond the capacity of this generator.
I was going to stop here but I wanted to talk about the load meter or power meter on the MEP generators, I think that would apply here. Some on this forum have talked about having readings that are inaccurate or erratic. First off, this is not a true load meter nor a power meter. It measures current not watts coming from the generator in amps and displaying it on a scale with percent of load where most amp meters have a display showing the amps in numbers. With scale showing percent of load I can see where the misconception comes from, but remembering that this is the maximum load or maximum amps coming from the generator, it does not measure the actual power consumption or watts of the load. The MEP 802 at 240 V single phase has a rating of 26 A, that is the maximum 24/7 output of current. Now let's put a resistive load on it. If you had an exact 6240 W load at 240 V you will be pulling 26A from the generator and your power meter should be reading 100%, this would be a 100% 24/7 load at 6240 watts. Now if we put a load with a 0.8 power factor and load gauge reads 100% the generator would be outputting 26 A, 26 A with a 0.8 power factor would be a consumption of 5000 W, this would be be the maximum 24/7 load, remember that gauge is reading output from the generator and not the reading of the actual load, the actual load is 5000 W. Now if we put on another load at a 0.6 power factor and the generator was outputting 26 A, the load gauge should read 100% and that would be a load of 3744 W. In this case 3744 W would be the maximum load that can be run 24/7, it seems like there's a loss of power somewhere, that power is called potential power and it is dissipated as heat. Just remember any time there's a 26 amps coming from the generator at 240 V your power meter should read 100%.Also if you are measuring the actual wattage of the load with a wattmeter and try to compare it to the load meter it will be all over the place and not make sense because one is reading watts and the load meter is reading amps, you can't compare the two. If you use a wattmeter to determine the maximum load of the generator or to balance loads, you will overload the generator. If your load meter does not read 100% with 26 A coming from the generator I have a meter calibration post that will be posted within a day or two. I hope I made this a lot clearer than mud.
Is this an extreme case? Yes, but the same thing affects any generator to some degree or other. It will affect a 100 W micro generator all the way up to a multi-megawatt power plant. Some of you already know what's going on here and what the problem is, this post is for those who do not. Could this setup run with this generator successfully? Yes, but I think that should be done in another post. If there enough interest in part 2, let me know and I will make one. Hopefully this post will help you understand why and how to prevent it. Everything in this post might not be technically 100% accurate, but I think it is perfect enough for this post.
There are several things going on with this scenario, but first we'll start off with some electrical terms that are involved here. I will list them and explain them the way it makes sense to me.
Volts – I think of this as pressure, such as pressure in a water line or an air line
Current – I think this as volume, bigger wire or bigger pipe equals larger volume
Amps – this is a measurement of current
Motor Idling – has nothing to do with RPM, it is a motor that is running but not doing any work
Power Factor – I think of this as the efficiency, low power factor low efficiency, high power factor high-efficiency. Best number here is 1.0
Potential Power – this is power that is produced but not used. I like to think of this as an air tank that has a leak. The bigger the leak the bigger the loss, the leak does not power anything but took power to produce it in the first place and continues taking power to keep the pressure in the tank high enough to do its intended work.
Watts – this is a measurement of power used, is not a measurement of power produced. This is what the utility companies use to know how much to charge you each month.
VA or volt amps – this is volts times amps. This can give an indication on power factor if you know the watts of the load. 100 W load at 1000 VA would be a very poor or low power factor 0.1. 800 W load at 1000 VA would be a good power factor 0.8. 1000 W load at 1000 VA would be a perfect power factor I.0. This would only be attainable with a resistive load.
To solve this problem we do not yet have enough information. Let's look at more information. Both motors are induction motors. First let's look at the drill press. The nameplate ratings are115 V - 9.8 full load amps. The actual readings with the motor sitting at idle, 123 V – 9.62 A – 350 W – 1190 VA – 0.3 power factor. This motor sitting at idle is drawing almost the same amount of amps as the nameplate rating at full load but is doing no work, and is only using 350 W of power, which is the power required to keep the motor running at its rated speed. So we are drawing 9.62 A from the generator to power 350 W, not very good. But what is happening to that excess power that the generator is outputting? That power would be what's called potential power, that is power produced but not used. But where does that power go, it has to go somewhere? Potential power gets dissipated as heat. As this motor gets put under more load, the watts will go up the power factor will go up and the amps will stay near the same and the generator will be producing less potential power and thus less heat. This motor is a three-quarter horse motor and should have a power factor rating of about 0.8, when I checked the power factor at maximum load I came up with 0.78, but I cannot say that that would be an accurate reading because I could not hold the full load steady enough and long enough to get an accurate reading. Same thing with the watts, it should be reading about 952 watts. I was going to list the results of the bench grinder, but the results were similar and would be redundant. In summary, the complete load of this set up is 2825 W which it seems the generator can handle without a problem, but the total load from the generator in amps is 75.35 at 120 V and that is beyond the capacity of this generator.
I was going to stop here but I wanted to talk about the load meter or power meter on the MEP generators, I think that would apply here. Some on this forum have talked about having readings that are inaccurate or erratic. First off, this is not a true load meter nor a power meter. It measures current not watts coming from the generator in amps and displaying it on a scale with percent of load where most amp meters have a display showing the amps in numbers. With scale showing percent of load I can see where the misconception comes from, but remembering that this is the maximum load or maximum amps coming from the generator, it does not measure the actual power consumption or watts of the load. The MEP 802 at 240 V single phase has a rating of 26 A, that is the maximum 24/7 output of current. Now let's put a resistive load on it. If you had an exact 6240 W load at 240 V you will be pulling 26A from the generator and your power meter should be reading 100%, this would be a 100% 24/7 load at 6240 watts. Now if we put a load with a 0.8 power factor and load gauge reads 100% the generator would be outputting 26 A, 26 A with a 0.8 power factor would be a consumption of 5000 W, this would be be the maximum 24/7 load, remember that gauge is reading output from the generator and not the reading of the actual load, the actual load is 5000 W. Now if we put on another load at a 0.6 power factor and the generator was outputting 26 A, the load gauge should read 100% and that would be a load of 3744 W. In this case 3744 W would be the maximum load that can be run 24/7, it seems like there's a loss of power somewhere, that power is called potential power and it is dissipated as heat. Just remember any time there's a 26 amps coming from the generator at 240 V your power meter should read 100%.Also if you are measuring the actual wattage of the load with a wattmeter and try to compare it to the load meter it will be all over the place and not make sense because one is reading watts and the load meter is reading amps, you can't compare the two. If you use a wattmeter to determine the maximum load of the generator or to balance loads, you will overload the generator. If your load meter does not read 100% with 26 A coming from the generator I have a meter calibration post that will be posted within a day or two. I hope I made this a lot clearer than mud.