## dumb question about quick charging

SageBrush
Posts: 4222
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017

### Re: dumb question about quick charging

lorenfb wrote:Ever attempted to determine which of the two phases powers

No, but as one of the brain dead I'd like to know the answer without the aid of a scope.
Any chance one phase goes to the left side of the panel and the other phase to the right ?
http://www.oempanels.com/208v-single-ph ... 8v-3-phase
Sheesh

And while I am on a roll of ignorance ... I'd like to understand 208 volt from a 120 volt WYE config (two phases connected)
I calculate it as 120 + 120*cos(pi/3) = 180 volts. Why is that wrong ?

Peace
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

lorenfb
Posts: 2221
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

### Re: dumb question about quick charging

SageBrush wrote:
lorenfb wrote:Ever attempted to determine which of the two phases powers

No, but as one of the brain dead I'd like to know the answer without the aid of a scope.
Any chance one phase goes to the left side of the panel and the other phase to the right ?
http://www.oempanels.com/208v-single-ph ... 8v-3-phase
Sheesh

And while I am on a roll of ignorance ... I'd like to understand 208 volt from a 120 volt WYE config (two phases connected)
I calculate it as 120 + 120*cos(pi/3) = 180 volts. Why is that wrong ?

Peace

Calculate Vrms = Vin (peak) x sqrt (1/2) x (1/pi) times the integral of: (sin(X) + sin(X+120) dx) |0 to 2pi

where Vin(peak) = Vrms X sqrt (2 )= 120 X 1.414 = 170 volts

If the phase angle were 180 degrees then the result is 240 versus 208.

Sorry for not being able to have the scientific keyboard characters. You'll get the idea.
Just a little integral calculus is all you need to remember.
Last edited by lorenfb on Wed Jul 03, 2019 10:31 am, edited 1 time in total.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F (35C), min discharge (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 25%, temp < 105F

lorenfb
Posts: 2221
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

### Re: dumb question about quick charging

For those that think that they understand residential power systems, consider what happens when the neutral power
line loses connection at the power pole, and your residence truly has a single phase (240 RMS, 340 PEAK) connected
to all your internal electrical devices, e.g. that switching power supply in your desktop PC, TVs & other electronics.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F (35C), min discharge (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 25%, temp < 105F

SageBrush
Posts: 4222
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017

### Re: dumb question about quick charging

lorenfb wrote:Calculate Vrms = Vin (peak) x sqrt (1/2) x (1/pi) times the integral of: (sin(X) + sin(X+120) dx) |0 to 2pi

Oh ... I see. Thanks!
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

lorenfb
Posts: 2221
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

### Re: dumb question about quick charging

SageBrush wrote:
lorenfb wrote:Calculate Vrms = Vin (peak) x sqrt (1/2) x (1/pi) times the integral of: (sin(X) + sin(X+120) dx) |0 to 2pi

Oh ... I see. Thanks!

Correction:

Vrms^2 = Vin (peak)^2 x (1/2pi) times the integral of: (sin(X) - sin(X+120))^2 dx |0 to 2pi
A book of math tables can be used to solve the above.

The simple case of being 180 degrees out of phase is; Vrms = 2 x Vin (peak) / sqrt (2) = 2 x Vin (RMS)
Last edited by lorenfb on Thu Jul 04, 2019 3:36 am, edited 1 time in total.
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F (35C), min discharge (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 25%, temp < 105F

SageBrush
Posts: 4222
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017

### Re: dumb question about quick charging

lorenfb wrote:
SageBrush wrote:
lorenfb wrote:Calculate Vrms = Vin (peak) x sqrt (1/2) x (1/pi) times the integral of: (sin(X) + sin(X+120) dx) |0 to 2pi

Oh ... I see. Thanks!

Correction:

Vrms^2 = Vin (peak)^2 x (1/2pi) times the integral of: (sin(X) + sin(X+120))^2 dx |0 to 2pi
A book of math tables can be used to solve the above.

The simple case of being 180 degrees out of phase is; Vrms = 2 x Vin (peak) / sqrt (2) = 2 x Vin (RMS)

When I looked at a picture of two vectors at 120 degrees to each other representing the voltage of each line I decided that the vector sum would remain constant. It still looks that way to me but it cannot be right and be AC so your integral is the way to go.

As for the details of calculating RMS of a waveform ... it is a distant memory.
When a multimeter measures 120 volts on an AC leg, is that an RMS value ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

GerryAZ
Gold Member
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Location: Phoenix, AZ

### Re: dumb question about quick charging

Sagebrush,

Multimeters are generally calibrated to display RMS voltage for sine waves. Depending upon their measurement methods, they may display incorrect voltages for other waveforms. True RMS meters will display RMS voltages for any waveform. For a sine wave, the RMS value is the peak value divided by the square root of 2. You are looking at the vectors correctly--line-to-line voltage between two phases (on a wye-connected transformer secondary) is the vectorial sum of the line-neutral voltages of those phases. The line-to-line voltage is the square root of 3 times the line-neutral voltage (120 Times Square root of 3 equals 208).
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015

lorenfb
Posts: 2221
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

### Re: dumb question about quick charging

SageBrush wrote:
lorenfb wrote:
SageBrush wrote:Oh ... I see. Thanks!

Correction:

Vrms^2 = Vin (peak)^2 x (1/2pi) times the integral of: (sin(X) + sin(X+120))^2 dx |0 to 2pi
A book of math tables can be used to solve the above.

The simple case of being 180 degrees out of phase is; Vrms = 2 x Vin (peak) / sqrt (2) = 2 x Vin (RMS)

When I looked at a picture of two vectors at 120 degrees to each other representing the voltage of each line I decided that the vector sum would remain constant. It still looks that way to me but it cannot be right and be AC so your integral is the way to go.

As for the details of calculating RMS of a waveform ... it is a distant memory.
When a multimeter measures 120 volts on an AC leg, is that an RMS value ?

The RMS voltage calculation determines what power will be developed from a particular voltage waveform.
RMS - root mean squared - the sqrt of the time average of the integral of the squared voltage function
#1 Leaf SL MY 9/13: 74K miles, 48 Ahrs, 5.2 miles/kWh (average), Hx=70, SOH=78, L2 - 100% > 1000, temp < 95F (35C), min discharge (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 115 Ahrs, 5.5 miles/kWh (average), Hx=98, SOH=99, DOD > 25%, temp < 105F

SageBrush
Posts: 4222
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017

### Re: dumb question about quick charging

GerryAZ wrote:Sagebrush,

Multimeters are generally calibrated to display RMS voltage for sine waves. Depending upon their measurement methods, they may display incorrect voltages for other waveforms. True RMS meters will display RMS voltages for any waveform. For a sine wave, the RMS value is the peak value divided by the square root of 2. You are looking at the vectors correctly--line-to-line voltage between two phases (on a wye-connected transformer secondary) is the vectorial sum of the line-neutral voltages of those phases. The line-to-line voltage is the square root of 3 times the line-neutral voltage (120 Times Square root of 3 equals 208).

Thanks for chiming in !

Would you mind showing the vector math that results in 120*sqrt (3) ?

I came up with 120 + 120*Cos(pi/3) = 120*1.5 but that is incorrect. I suppose it means that I cannot simply take the vectorial sum of the two RMS voltages
2013 LEAF 'S' Model with QC & rear-view camera
Bought off-lease Jan 2017 from N. California
Car is now enjoying an easy life in Colorado
03/2018: 58 Ahr, 28k miles
11/2018: 56.16 Ahr, 30k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

SageBrush
Posts: 4222
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017