Mike, just an FYI on the no EMS units having overloaded neutral protection. In November 2014 I sent this question to Thomas E. Fanelli, President Progressive Industries, Inc. He acknowledged the problem and said he has been working on it. By February 2015 I had a prototype board installed in my EMS-LCHW50 for testing. Almost a year later I had a functioning prototype board in my EMS that would trap the overloaded neutral. Thomas told me that it was planned to be in a new product soon but I never heard another word about it. Too bad he didn't continue with the project.
Mike, as to e.g. L1=10a, L2=25a, N=15a, I agree IF you have linear loads that don’t produce harmonic loads. So in these types of nonlinear loads (like switch mode power supplies), the L1 and L2 currents don’t always cancel, and can be additive. As to how many loads in an RV are nonlinear, that is a variable. 🤔
In a network command center that I once designed (208v 3 phase), we never shared neutrals from phase to phase. Each phase had dedicated neutrals back to the power panel.
I was assuming split-phase loads for my examples. In that case the two legs are 180 degrees out of phase so load currents and harmonics from PWM power supplies should be subtractive on the neutral. But as you mention, 3-phase 208-volt service has the legs at 120 degrees of phase shift. And that's what causes the Triplen harmonics (3rd, 5th, 7th order, etc...) to become additive current on the neutral. I did a lot of concert lightning power in the 80's when SCR/TRIAC dimmers and Halogen bulbs were used in huge quantities for rock stages. And because we connected to 3-phase power many times we ran a double neutral to our dimmer racks. That was needed to prevent the neutral from overheating from the Triplen harmonics you mentioned. Good times!
Mike, just an FYI on the no EMS units having overloaded neutral protection. In November 2014 I sent this question to Thomas E. Fanelli, President Progressive Industries, Inc. He acknowledged the problem and said he has been working on it. By February 2015 I had a prototype board installed in my EMS-LCHW50 for testing. Almost a year later I had a functioning prototype board in my EMS that would trap the overloaded neutral. Thomas told me that it was planned to be in a new product soon but I never heard another word about it. Too bad he didn't continue with the project.
I believe that’s around the time the Fanelli brothers sold their company.
Mike, as to e.g. L1=10a, L2=25a, N=15a, I agree IF you have linear loads that don’t produce harmonic loads. So in these types of nonlinear loads (like switch mode power supplies), the L1 and L2 currents don’t always cancel, and can be additive. As to how many loads in an RV are nonlinear, that is a variable. 🤔
In a network command center that I once designed (208v 3 phase), we never shared neutrals from phase to phase. Each phase had dedicated neutrals back to the power panel.
I was assuming split-phase loads for my examples. In that case the two legs are 180 degrees out of phase so load currents and harmonics from PWM power supplies should be subtractive on the neutral. But as you mention, 3-phase 208-volt service has the legs at 120 degrees of phase shift. And that's what causes the Triplen harmonics (3rd, 5th, 7th order, etc...) to become additive current on the neutral. I did a lot of concert lightning power in the 80's when SCR/TRIAC dimmers and Halogen bulbs were used in huge quantities for rock stages. And because we connected to 3-phase power many times we ran a double neutral to our dimmer racks. That was needed to prevent the neutral from overheating from the Triplen harmonics you mentioned. Good times!