This video is helpful but I felt two things it said are somewhat misleading and I thought it missed an opportunity to point out the efficacy benefits of 3-phase power.
First, while the “speed” of electrons in a conductor is proportional to the applied electric field and the electron mobility in that specific conductor, the actual electron velocity is extremely slow (microns per second) because it is limited by electron-atom collisions (at the atomic scale) while the speed of an electric signal approaches the speed of light. These two aspects are confusing and are not necessary to explain 3-phase power in a basic video like this. It may be more helpful to think of current flow in an electric circuit being proportional to applied voltage rather than thinking in terms of the electron velocity which is different in the highly conductive portions (the wires)and the resistive portion (the load) of the circuit where most all of the power is dissipated.
Second, while lights do “flicker” with the applied voltage, the temporal response of the eye limits our ability to perceive it. Light is generated in each half cycle in old style incandescent and fluorescent lights at twice the line frequency or 100/120 Hz for 50/60 Hz power systems which is near the edge of human perception. Incandescent lamps have built/in thermal inertia that reduces flicker. Fluorescent lights have more perceivable flicker than incandescent lights. However, modern LED lights operate on DC and don’t flicker.
I agree with video’s point that 3-phase power is capable of delivering more average and instantaneous power than split phase but I believe there are better ways to say it. They could have said that power delivery in a 3-phase circuit never drops to zero in each cycle as it does with split phase and that 3-phase systems deliver 1.73 times more power with the same amount wire compared to a split phase system making it more efficient in both industrial and commercial settings.
Of course, it also makes sense to use 3-phase in campgrounds for the same reasons. However, the price to be paid is that the complexity is higher (e.g., there are multiple 3-phase wiring configurations as Mike has explained in other articles).
So if I understand you, L1&L2 or L2&L3 or L1&L3 will read 208vac and that's acceptable at the pedestal for your RV.
Does that mean that a commercial building supplied with 3 phase only will see 208vac at the water heater, HVAC system, dryer, etc?? If so, are what happens to all the HVAC systems not rated at 208, or the roof top AC on an RV...
Are we connecting these appliances to known low voltage??
You are correct for a 208/120-volt Wye service. And many single-phase or 3-phase commercial products can be designed for 208 or 240 volts.
Or you can add a buck/boost transformer to each phase that will boost 208-volts up to 240-volts.
Note that a High-Leg Delta service creates 240-240-240 volts between the 3 phases with two of the legs measuring 120-volts to neutral. But the third “High” leg measures 208-volts to neutral.
This video is helpful but I felt two things it said are somewhat misleading and I thought it missed an opportunity to point out the efficacy benefits of 3-phase power.
First, while the “speed” of electrons in a conductor is proportional to the applied electric field and the electron mobility in that specific conductor, the actual electron velocity is extremely slow (microns per second) because it is limited by electron-atom collisions (at the atomic scale) while the speed of an electric signal approaches the speed of light. These two aspects are confusing and are not necessary to explain 3-phase power in a basic video like this. It may be more helpful to think of current flow in an electric circuit being proportional to applied voltage rather than thinking in terms of the electron velocity which is different in the highly conductive portions (the wires)and the resistive portion (the load) of the circuit where most all of the power is dissipated.
Second, while lights do “flicker” with the applied voltage, the temporal response of the eye limits our ability to perceive it. Light is generated in each half cycle in old style incandescent and fluorescent lights at twice the line frequency or 100/120 Hz for 50/60 Hz power systems which is near the edge of human perception. Incandescent lamps have built/in thermal inertia that reduces flicker. Fluorescent lights have more perceivable flicker than incandescent lights. However, modern LED lights operate on DC and don’t flicker.
I agree with video’s point that 3-phase power is capable of delivering more average and instantaneous power than split phase but I believe there are better ways to say it. They could have said that power delivery in a 3-phase circuit never drops to zero in each cycle as it does with split phase and that 3-phase systems deliver 1.73 times more power with the same amount wire compared to a split phase system making it more efficient in both industrial and commercial settings.
Of course, it also makes sense to use 3-phase in campgrounds for the same reasons. However, the price to be paid is that the complexity is higher (e.g., there are multiple 3-phase wiring configurations as Mike has explained in other articles).
So if I understand you, L1&L2 or L2&L3 or L1&L3 will read 208vac and that's acceptable at the pedestal for your RV.
Does that mean that a commercial building supplied with 3 phase only will see 208vac at the water heater, HVAC system, dryer, etc?? If so, are what happens to all the HVAC systems not rated at 208, or the roof top AC on an RV...
Are we connecting these appliances to known low voltage??
Did I say this so it's understandable
Thanks
You are correct for a 208/120-volt Wye service. And many single-phase or 3-phase commercial products can be designed for 208 or 240 volts.
Or you can add a buck/boost transformer to each phase that will boost 208-volts up to 240-volts.
Note that a High-Leg Delta service creates 240-240-240 volts between the 3 phases with two of the legs measuring 120-volts to neutral. But the third “High” leg measures 208-volts to neutral.
So your thoughts on connecting a home hvac unit to a know 208vac circuit... in my book this is low voltage by the way I was taught....
Your thoughts please.. or is 208vac now considered acceptable?
Is this a mini-split or a conventional central air conditioner? And very few residences have 3-phase power.