EV

[liaxx2023]

They are installing a 150kVA 3-phase 480V delta - 208 Y 120 and a commercial building has a 200A 480V three-phase for EV chargers. The charger to use is a single-phase 208V with an input current of 48A.

Am I correct that the max numbers of chargers allowed for this system is 3?

 

[Dennis Alwon]

I get 4 ev units. I assumed continuous load so 200 amps * .8 = 160 amps. With 3 phase you will have a max of 3 units on 2 phases and 2 units on the other phase.

3* 48 = 144 amps

AB
BC
AC
AB

 

[liaxx2023]

I get 4 ev units. I assumed continuous load so 200 amps * .8 = 160 amps. With 3 phase you will have a max of 3 units on 2 phases and 2 units on the other phase.

3* 48 = 144 amps

AB
BC
AC
AB

with a 60A OCPD on each branch?

 

[wwhitney]

If we assume the 480V 3 phase service has a 200A non-100% rated OCPD, and that the EVSEs must be treated as continuous loads, then the available continuous VA at the 480V 3-phase service is 200*480*sqrt(3)/125% = 133 kVA for a balanced load. The transformer rating of 150 kVA is a continuous rating to my understanding, so the 133 kVA is the limiting factor.

(3) 208V 48A continuous EVSEs in a balanced configuration present a continuous load of 3*208*48 = 30 kVA. So certainly 4 such sets, or 12 EVSEs, can be supplied from the equipment, as 4*30 kVA = 120 kVA < 133 kVA.

To check the unbalanced case (i.e. a 13th EVSE, since there is more than 10 kVA remaining), the allowable continuous current on the 208Y/120V system is 200A * 480/208 * (1/125%) = 369A. (4) balanced sets of 48A 2-wire EVSEs load one leg to 48*4*sqrt(3) = 333A. One additional 2-wire load imposes an additional current of 48A at a 30 degree phase angle to the 333A. 48A * cos(30 degrees) = 42A, which already makes 375A without including the effect of the perpendicular current component. So there's no room in the load calc for a 13th EVSE.

Cheers, Wayne

 

[augie47]

If the 480 circuit is protected by a 200 amp breaker and you have a 150 kva transformer you may experience some unwanted tripping due to inrush current..

 

[liaxx2023]

If we assume the 480V 3 phase service has a 200A non-100% rated OCPD, and that the EVSEs must be treated as continuous loads, then the available continuous VA at the 480V 3-phase service is 200*480*sqrt(3)/125% = 133 kVA for a balanced load. The transformer rating of 150 kVA is a continuous rating to my understanding, so the 133 kVA is the limiting factor.

(3) 208V 48A continuous EVSEs in a balanced configuration present a continuous load of 3*208*48 = 30 kVA. So certainly 4 such sets, or 12 EVSEs, can be supplied from the equipment, as 4*30 kVA = 120 kVA < 133 kVA.

To check the unbalanced case (i.e. a 13th EVSE, since there is more than 10 kVA remaining), the allowable continuous current on the 208Y/120V system is 200A * 480/208 * (1/125%) = 369A. (4) balanced sets of 48A 2-wire EVSEs load one leg to 48*4*sqrt(3) = 333A. One additional 2-wire load imposes an additional current of 48A at a 30 degree phase angle to the 333A. 48A * cos(30 degrees) = 42A, which already makes 375A without including the effect of the perpendicular current component. So there's no room in the load calc for a 13th EVSE.

Cheers, Wayne

Thank you for this, Wayne. Given that EVSE must be considered as continuous loads, (48A x 1.25) meaning the ocpd rating for the charger branch circuit should be 60A?

 

[wwhitney]

Thank you for this, Wayne. Given that EVSE must be considered as continuous loads

Just to clarify, 625 doesn't actually say that. It says that the OCPD has to be sized as if it is a continuous load. Not much of a difference with 1 EVSE, but I've haven't thought out if the consequences are different when you have 12 or more EVSEs.

(48A x 1.25) meaning the ocpd rating for the charger branch circuit should be 60A?

Yes, that part is certainly correct.

Cheers, Wayne

 

[liaxx2023]

Just to clarify, 625 doesn't actually say that. It says that the OCPD has to be sized as if it is a continuous load. Not much of a difference with 1 EVSE, but I've haven't thought out if the consequences are different when you have 12 or more EVSEs.


Yes, that part is certainly correct.

Cheers, Wayne

Another question here, how did we come up with a max of 3 EVSEs per phase in a balanced configuration?

 

[wwhitney]

Another question here, how did we come up with a max of 3 EVSEs per phase in a balanced configuration?

We didn't. We considered groups of 3 EVSEs to balance the 2-wire loads among the 3 legs of the supply (so each group connected AB, BC, and CA). And I calculated a maximum of 4 such groups, so 12 EVSEs total.

Cheers, Wayne

 

[Johnhall30]

I believe he is saying that (three) ESVEs single-phase, on AB, AC, and BC creates a balanced configuration

 

[liaxx2023]

We didn't. We considered groups of 3 EVSEs to balance the 2-wire loads among the 3 legs of the supply (so each group connected AB, BC, and CA). And I calculated a maximum of 4 such groups, so 12 EVSEs total.

Cheers, Wayne

Oh got it, was confused on that one. Thanks a lot, much appreciated!

 

[liaxx2023]

We didn't. We considered groups of 3 EVSEs to balance the 2-wire loads among the 3 legs of the supply (so each group connected AB, BC, and CA). And I calculated a maximum of 4 such groups, so 12 EVSEs total.

Cheers, Wayne

Does it make any difference if the transformer to be installed is a step-down transformer 150kVa (480V delta - 208 Y 120)? or they're just the same?

 

[GregoryStellar]

If we assume the 480V 3 phase service has a 200A non-100% rated OCPD, and that the EVSEs must be treated as continuous loads, then the available continuous VA at the 480V 3-phase service is 200*480*sqrt(3)/125% = 133 kVA for a balanced load. The transformer rating of 150 kVA is a continuous rating to my understanding, so the 133 kVA is the limiting factor. Here.

(3) 208V 48A continuous EVSEs in a balanced configuration present a continuous load of 3*208*48 = 30 kVA. So certainly 4 such sets, or 12 EVSEs, can be supplied from the equipment, as 4*30 kVA = 120 kVA < 133 kVA.

To check the unbalanced case (i.e. a 13th EVSE, since there is more than 10 kVA remaining), the allowable continuous current on the 208Y/120V system is 200A * 480/208 * (1/125%) = 369A. (4) balanced sets of 48A 2-wire EVSEs load one leg to 48*4*sqrt(3) = 333A. One additional 2-wire load imposes an additional current of 48A at a 30 degree phase angle to the 333A. 48A * cos(30 degrees) = 42A, which already makes 375A without including the effect of the perpendicular current component. So there's no room in the load calc for a 13th EVSE.

Cheers, Wayne

I also think that the ocpd rating for the charger branch circuit should be 60A!