Just when I thought I understood that single phase = 120/220 volt, center tapped transformer, you go and shake up that assumption. I'm not a sparky, but always been. interested in electrical/electronics. There's already lot of misconception out there with referring to 220v as being 3 phase. Especially in buying equipment: people love to refer to 220v motors as 3 phase... The rabbit hole runs deep!!!
Ryan thanks for another great vid. Was told a few years ago at a continuing education class that it is very important to do an availble short circuit calculation whenever replacing the customer owned transformer espically when using the now lower impedance transformers. Also have to be carefull with large services. At large hospital that I retired from somebody pulled out some spare 600 to 1200 amp 480 volt circuit breakers while performing yearly PM'S & testing that were only rated for think it was 65KIA and installed them in other switchboard that was feed from another dual rated setvice but with had think it was 600 to 1200 amp breakers that were rated for at least 90 KIA thetefore limiting that switchboard to only 65 KIA or in other words the lowest avaible KIA. Took boss a while to belive this serous mistake.
I’m a high voltage apprentice and I see larger transformers almost everyday this is a extremely well made video describing how these transformers work especially for people even less experienced than me well done
Most 2 phase that I came across was 240 volt 5 wire. The 5th wire was 120 volts to the other 4.phase wires. We had a 2 phase 3 wire 2300 volt feed to another building where they place a phase wire from each of the 2.phases and draws 1.41 more amps. They also had 480 volt 2 phase.
In my 50 years never saw a corner grounded Delta transformer. You mentioned that you are not allowed to fuse the corner grounded wire but would a 3 pole circuit breaker be okay. Had at least 40 hours of transformer in vo tech class back in the 60's but do not remember that. Helped my sparky dad install a 2300 volt service to a Scott T transformer that put out both 2 & 3 phase voltage. The electrical vault was very small and only had room for 1 transformer. Kind if remember that open Delta does not provide as good as a voltage regulation but the ultily companies love them due to increase available setvice only have to install a third transformer.
Thank you Ryan Jackson, keep up the hard work! Have been watching all your videos and appreciate every single one of them. Here located in the Richland, Washington (Hanford area). Come visit us sometime
Open Delta: Understand now. All three (3) power company phases are connected to the primary coils (2) even though only (2) coils in the SECONDARY side of the transformer(s). 54% as powerful as closed delta system. Thank you.
Ryan I have a question on autotransformers and what you mentioned the 20% general rule. So if single phase autotransformers only have 3 wires what would the 4 wire ( extra conductor for gounding conductor = white wire ) that our ultilty company uses be called? They only provide 1 wire from the 13, 200 three phase on a pole to step down the voltage down to 120/240 volts. They ground one side of medium voltage to transformer case, a flimsy ground rod at bottom of pole and to what appears to the center tap on secondary to grounded conductor. To me the ground rod would never have low enough resistance to feed majority of current for primary winding so grounded conductor along with our copper water service and metal gas pipe is back feeding current to feed transformer. Cracks me up how ultily company gets away with splicing ground wire 3 or 4 times that only runs 30' down the pole. Wire from transformer starts out as copper that somebody stole a 6' section. Then they climbed up and stole a couple of more feet of copper. Luckily they use aluminum to replace the copper and that lasts longer. Thanks.
Nice video, just wanted to mention that In a 2-phase system the 170v that you mention was not usable is not accurate as it was used at those times. I don’t wish to go into detail but that is an important thing to know.
In the three phase high leg Delta example, where the B phase is the high leg, (14:46 min in video) the 208 V circuit to ground could be useful for some 208v lighting circuits or even a single phase mini split HVAC unit rated for that voltage. Once the conductor leaves the panel, it would be no different than any phase conductor on a 208/480 used for lighting loads in commercial applications…. What hoops would you have to go through to be able to use that phase for single phase loads?
Only problem with a ungrounded system that has the 3 ground indicating lights is trying to locate a ground. We had this back in the 1970's at a large slaughterhouse that I worked on. Could only really work on finding a ground was on Saturday when there was no production. Would start in substation turning off 400 to 800 amp breakers then going downstream. Majority of the time is was from a grounded motor. At that place we replaced at least 1 to 3 bad motors a week. Record was replaced 3 bad 100HP motors on one very hot day during a ultily brownout. I had my last long transformer class 50 years ago so I think they told us with an open delta voltage regulation was not as good as a closed delta.
Thanks Ryan from a retired master electrician from Wisconsin....I don’t do this stuff anymore but I have had a love affair with electricity for 45!years and I enjoy your video’s
Wow. Very cool video, I wished you were my former instructor in the electronics class I attended all too many yrs ago lol. I never understood the concept of two phase five wire or how it was hooked up, or that it is still in service near Philadelphia area, I have only heard of it, and that it was pretty common in the 1890s to very early 1900s, i think the first poly phase system invented by Nicola Tesla used the configuration to power some very early electric motors, but was soon phased out to more efficient 3 phase systems that we to this day, still use.
You may be aware that in New York City (and possibly Westchester County??) Con Ed distributes two legs of their three phase network 120/208V wye system to "single phase" residential households. Two phases (208V, not 240) and the neutral. Your neighbor may well get one leg of the third phase and one of the same legs you got. Most people are unaware of this, although I'd assume that any licensed electrician in NYC is. I've had to explain this to many of my EE friends who couldn't understand why the supposed 240 volts between the two hot legs of their service only measured 208V. If you are in a part of NYC with overhead distribution, it is very visible, four secondary conductors with only three connected to each service drop, a different three (but always the neutral) to each drop. Second item of interest: At a university on Long Island I worked for in the 1970's the original university owned primary and secondary distribution was two phase five wire. The primary was two phase three wire, two 2400V legs and a ground return for the two of them. The transformers for each building were two (very old) single phase transformers each with a 120/240V secondary as you drew. The campus was built new in 1929, so I'd have to guess that the utility distribution in the area was two phase, but I was never able to find the history. LILCO, the then utility fed us with a pair of scott-tee transformers from their (then) 4160V three phase delta primary distribution to our 2400V service. While I was there, we rewired the remaining buildings with "more modern" 120/208V three phase distribution fed from a new 13KV service. However the cafeteria was full of two phase four wire (no neutral) motors, and rather than rewinding or replacing them all, a 120/208 to 240V three phase to two phase scott-tee transformer was installed to feed them all. My other involvement with two phase power and scott-tee transformers was with mercury vapor rectifier banks. Both low voltage (carbon arc lamp supplies for 35mm motion picture projectors) and many KV supplies (for broadcast transmitter tubes) often used scott-tee transformers with four rectifier tubes.
Ahah, so that explains where the 2400 volt electric chair came from then. Rather than risk blowing up the transformers, they just ran service conductors to the chair straight from the primary. Well, I guess you could call them "feeders" since they would have a service disconnecting means for the executioner to close, but probably no overcurrent protection. The first overcurrent protective device was the person in the chair..... LOL
@@brnmcc01 I would suspect that the 2400V electric chair was fed from a pole transformer connected in reverse, the 120V or 240V connected from the building power (where it can more safely turned on and off) and the 2400V side which normally would have been the primary now fed to the electric chair electrodes.
HI,,,RYAN,question is permit make the raceway inside the transformer in the pads concrete????may i use PVC,i have seen in miami building but im not sure is legal????CASANOVA ELECTRIC CONTRACTOR
Although I have an _”ancient”_ (1976) degree in electrical engineering, I do have one question: In an area where both 12 Kv and 4 kv distribution systems are used, as a rule of thumb, is one more susceptible than the other to subjecting the end user (120/240v, 1Φ, 3 wire, overhead) to lightning and/or switching surges? For example, would a lightning strike (direct or indirect) to a 12 kV line get stepped down in voltage more before entering a home than a similar strike to a 4 kV system? Or does lightning not obey the usual mathematics of a transformer’s turns ratio?
Thank you Ryan.. I was always confused about all the different types of systems out there.. I found your channel because I was trying to learn about .. Swimming pool safety.. through Mike Holt videos .. I have learned so much information from the both of you .. Thank you so much
@@RyanJacksonElectrical I have a hayward low voltage transformer . 120vac 2amp max ..output 14vac 70 va I have the 70watt junction box kit with transformer.. all plastic.. The instructions say to land the ground wire from feed on ground bar in J box ..but also they state to land bonding grid to this bar as well .. so I will have bonding grid and equipment ground on same bar .. is this ok ??
@@RyanJacksonElectrical Thank you Ryan.. I for some reason was worried about bonding grid and equipment ground of pool panel being together..code saying it is not necessary to bring grid to the panel board.. 680.26 (C) .. and also a healthy fear ...Being a new pool owner is certainly a big responsibility..
Thank you for posting on your channel. The info you share is a goldmine from anyone that is an apprentice all the way up to master. Thank you so much for posting content. I know I am not the only one that appreciates your hard work.
I got to the end of this video, disappointed because I didn't see the configuration for which I was searching when I clicked. The configuration I was hoping to see is the one that enters a residence (i.e., 120/240 grounded). Did I miss it?
Single Phase 2W systems are actually very common in North America if you work with Control Transformers, or in a panelshop. Typically in the 100-2000VA size, 600-120V (Canada) and 480V-120V (USA). Great presentation!
Hey Ryan, it seems like the math works the same on the open Delta system using the Pythagorean theorem to get 240v between the two points on the open end. It’s just a little confusing to me that you can get 240v between the two points on the open ends. And use the math the same way if you were to draw an imaginary line between the two open points. Or am I over thinking it?
If there is a neutral wire on a wye 480/277 secondary, does the wounding has to be grounded ? Can that neutral be floating? And why? Thanks! Very good class.
You're allowed to have an ungrounded 480V wye (but not 208) , but you can not hook up the neutral because any circuit that uses a neutral MUST come from a grounded system. I'm sure there is an obscure application where an ungrounded wye would be useful as opposed to an ungrounded delta, but I'm drawing a blank.
@@RyanJacksonElectricalFor 480v three phase 3wire ungrounded systems you can use 240/480 v transformers wired delta, or 277v transformers wired wye. Because 277/480v three phase 4wire grounded systems are real common, due to having 277v in inventory we just build 480v three phase 3 wire ungrounded ( floated) with them.
North America, do we use SWER (single wire earth return) from the (single phase) step down pole mounted transformer to the substation? I see no neutral from the transformer(s) thank you
We use a multi-grounded neutral, which is to say that we have the grounded/neutral conductor that goes from pole to pole and from pole to the customer, and we ground it at every transformer and pole.
The neutral for the primary is the same neutral being used on the secondary. We call it a common neutral system. The primary bushing is for hot primary conductor and the other end of the winding is attached to case of transformer. As long as the common neutral is attached to the case then the primary winding has two different potential conductors across winding.
@@RyanJacksonElectrical Question please. Reference the “Multi point grounded neutral system. (Thousands of them) Philadelphia area single phase step down transformers I can not see a NEUTRAL conductor going from pole to pole? This SHOULD BE in parallel with the MENTIONED multi-point system which is obvious at every pole? Thank you.
Installed a 3 phase & single phase service to a Philly store about 10 years ago. The area still had 2 phase power. Ultility company installed a phase changer then if memory served me right only brought in 5 wires. One conductor was used for the single & 3 phase service. Bad thing about 2 phase if you cross feed wires to a 4 wire 2 phase motor it would only recieve around 180 volts instead of 240 volts burning motor out. At the large hospital/ research centers that I retired from probably had over 200 480 to 120/208 Delta to Wye transformers. They had a few 208 to 240 volt transformers for some small equipment. Thanks for another easy to follow informative vid.
Thanks Ryan. I have not connected a two phase motor here in Philly since the 1980's. Was in an old machine shop. For fun I did a Google search and could not find any 240 volt 4 pole 4 fuse 30 amp safety switches that I had I stalled a few back in the 1970's for two phase.
On the 3 single phase 4 wire system , the grounding wire coming down the pole from the 3 single pole XMFRs, If that ground wire got cut by a vehicle accident, what would it do to the voltages ?
It really wouldn't do anything, for two reasons. First, and unlike the transformers we install, the utility connects both the primary and the secondary to the frame of the transformer and ultimately to their neutral point. This means there are thousands of those connections throughout the distribution system, so cutting one wouldn't really be problematic. Second, when we measure voltage we usually measure to the metal parts, not to the actual dirt itself. If you cut the wire going to the dirt, but kept the wire connecting the windings to the metal parts, you would still have a predictable voltage from the conductors to the metal parts.
@@RyanJacksonElectrical Good point. Another interesting thing with high leg 120/240 delta systems is, if you lose one of the smaller transformers that doesn't have a center tap, is you don't single phase your motors, everything still will work, like an open leg or ghost leg 240 delta system, you will just have much less KVA capacity until the utility can come and replace the can on the pole, or the HV fuse etc. If you lose a leg on a 208Y120 system, then you get all kinds of strange voltages on your 120v circuits from current backfeeding the dead leg from 208v loads, and 3 phase motors trip on thermal overload, or burn out. Replaced many burned out compressors over the years from that happening where a tree or vehicle accident or other object coming into contact with the POCO distribution lines causing a loss of one phase for awhile.
It is truly amazing how much technology has brought to the trade. I USED to think that I knew practically everything from 30 years in the trade. Ryan’s channel is my new “go to” place for everything electrical! He doesn’t have the fancy peanut gallery of experts like Mike Holt, 😉 but he sure does explain things in a straightforward and easy to understand way. AND.... As Sleepy-Joe Biden would say..... “C’MON MAN -->>> PUT YOUR DAMN MASK ON !” 😷😆🤣 🇺🇸😥🇺🇸
Great video I might have to watch it over and over , but definitely getting more and more familiar with transformers , thanks !
Just when I thought I understood that single phase = 120/220 volt, center tapped transformer, you go and shake up that assumption. I'm not a sparky, but always been. interested in electrical/electronics. There's already lot of misconception out there with referring to 220v as being 3 phase. Especially in buying equipment: people love to refer to 220v motors as 3 phase... The rabbit hole runs deep!!!
Learned so much... Ryan you're quickly becoming my favorite teacher. Thank you so much for what you do for our industry.
Ryan thanks for another great vid. Was told a few years ago at a continuing education class that it is very important to do an availble short circuit calculation whenever replacing the customer owned transformer espically when using the now lower impedance transformers. Also have to be carefull with large services. At large hospital that I retired from somebody pulled out some spare 600 to 1200 amp 480 volt circuit breakers while performing yearly PM'S & testing that were only rated for think it was 65KIA and installed them in other switchboard that was feed from another dual rated setvice but with had think it was 600 to 1200 amp breakers that were rated for at least 90 KIA thetefore limiting that switchboard to only 65 KIA or in other words the lowest avaible KIA. Took boss a while to belive this serous mistake.
What they actually did if the AFC was greater than 65kA was install essentially bombs in that switchgear.
I’m a high voltage apprentice and I see larger transformers almost everyday this is a extremely well made video describing how these transformers work especially for people even less experienced than me well done
Thanks Michael!
Thanks ryan. If transformer not grounded, is it functioning properly?
Thank you. I really enjoyed this one. I never knew of 2 phase in USA.
Thanks so much, glad you enjoyed it.
Most 2 phase that I came across was 240 volt 5 wire. The 5th wire was 120 volts to the other 4.phase wires. We had a 2 phase 3 wire 2300 volt feed to another building where they place a phase wire from each of the 2.phases and draws 1.41 more amps. They also had 480 volt 2 phase.
I thought Transformers were robots in disguise just kidding thanks for the wealth of knowledge you share
In my 50 years never saw a corner grounded Delta transformer. You mentioned that you are not allowed to fuse the corner grounded wire but would a 3 pole circuit breaker be okay. Had at least 40 hours of transformer in vo tech class back in the 60's but do not remember that. Helped my sparky dad install a 2300 volt service to a Scott T transformer that put out both 2 & 3 phase voltage. The electrical vault was very small and only had room for 1 transformer. Kind if remember that open Delta does not provide as good as a voltage regulation but the ultily companies love them due to increase available setvice only have to install a third transformer.
Some utility companies use open delta because the customer has some 3 phase loads but not enough to call for a closed system.
great,video RYAN,thanks,casanova EC
Thank you Ryan Jackson, keep up the hard work! Have been watching all your videos and appreciate every single one of them. Here located in the Richland, Washington (Hanford area). Come visit us sometime
Open Delta: Understand now. All three (3) power company phases
are connected to the primary coils (2) even though only (2) coils in the SECONDARY side of
the transformer(s). 54% as powerful as closed delta system. Thank you.
Ryan I have a question on autotransformers and what you mentioned the 20% general rule. So if single phase autotransformers only have 3 wires what would the 4 wire ( extra conductor for gounding conductor = white wire ) that our ultilty company uses be called? They only provide 1 wire from the 13, 200 three phase on a pole to step down the voltage down to 120/240 volts. They ground one side of medium voltage to transformer case, a flimsy ground rod at bottom of pole and to what appears to the center tap on secondary to grounded conductor. To me the ground rod would never have low enough resistance to feed majority of current for primary winding so grounded conductor along with our copper water service and metal gas pipe is back feeding current to feed transformer. Cracks me up how ultily company gets away with splicing ground wire 3 or 4 times that only runs 30' down the pole. Wire from transformer starts out as copper that somebody stole a 6' section. Then they climbed up and stole a couple of more feet of copper. Luckily they use aluminum to replace the copper and that lasts longer. Thanks.
Nice video, just wanted to mention that In a 2-phase system the 170v that you mention was not usable is not accurate as it was used at those times. I don’t wish to go into detail but that is an important thing to know.
In the three phase high leg Delta example, where the B phase is the high leg, (14:46 min in video) the 208 V circuit to ground could be useful for some 208v lighting circuits or even a single phase mini split HVAC unit rated for that voltage. Once the conductor leaves the panel, it would be no different than any phase conductor on a 208/480 used for lighting loads in commercial applications…. What hoops would you have to go through to be able to use that phase for single phase loads?
I'm a new subscriber sir, can you explain how secondary 3 phase 3 wire system is derived from transformer bank with single phase primary? Thank you
Only problem with a ungrounded system that has the 3 ground indicating lights is trying to locate a ground. We had this back in the 1970's at a large slaughterhouse that I worked on. Could only really work on finding a ground was on Saturday when there was no production. Would start in substation turning off 400 to 800 amp breakers then going downstream. Majority of the time is was from a grounded motor. At that place we replaced at least 1 to 3 bad motors a week. Record was replaced 3 bad 100HP motors on one very hot day during a ultily brownout. I had my last long transformer class 50 years ago so I think they told us with an open delta voltage regulation was not as good as a closed delta.
Thank you for this Ryan, appreciate the effort to put it together.
Thanks Ryan from a retired master electrician from Wisconsin....I don’t do this stuff anymore but I have had a love affair with electricity for 45!years and I enjoy your video’s
Wow. Very cool video, I wished you were my former instructor in the electronics class I attended all too many yrs ago lol. I never understood the concept of two phase five wire or how it was hooked up, or that it is still in service near Philadelphia area, I have only heard of it, and that it was pretty common in the 1890s to very early 1900s, i think the first poly phase system invented by Nicola Tesla used the configuration to power some very early electric motors, but was soon phased out to more efficient 3 phase systems that we to this day, still use.
You may be aware that in New York City (and possibly Westchester County??) Con Ed distributes two legs of their three phase network 120/208V wye system to "single phase" residential households. Two phases (208V, not 240) and the neutral. Your neighbor may well get one leg of the third phase and one of the same legs you got. Most people are unaware of this, although I'd assume that any licensed electrician in NYC is. I've had to explain this to many of my EE friends who couldn't understand why the supposed 240 volts between the two hot legs of their service only measured 208V.
If you are in a part of NYC with overhead distribution, it is very visible, four secondary conductors with only three connected to each service drop, a different three (but always the neutral) to each drop.
Second item of interest: At a university on Long Island I worked for in the 1970's the original university owned primary and secondary distribution was two phase five wire. The primary was two phase three wire, two 2400V legs and a ground return for the two of them. The transformers for each building were two (very old) single phase transformers each with a 120/240V secondary as you drew. The campus was built new in 1929, so I'd have to guess that the utility distribution in the area was two phase, but I was never able to find the history. LILCO, the then utility fed us with a pair of scott-tee transformers from their (then) 4160V three phase delta primary distribution to our 2400V service.
While I was there, we rewired the remaining buildings with "more modern" 120/208V three phase distribution fed from a new 13KV service. However the cafeteria was full of two phase four wire (no neutral) motors, and rather than rewinding or replacing them all, a 120/208 to 240V three phase to two phase scott-tee transformer was installed to feed them all.
My other involvement with two phase power and scott-tee transformers was with mercury vapor rectifier banks. Both low voltage (carbon arc lamp supplies for 35mm motion picture projectors) and many KV supplies (for broadcast transmitter tubes) often used scott-tee transformers with four rectifier tubes.
Was that in Garden City - the University?
Ahah, so that explains where the 2400 volt electric chair came from then. Rather than risk blowing up the transformers, they just ran service conductors to the chair straight from the primary. Well, I guess you could call them "feeders" since they would have a service disconnecting means for the executioner to close, but probably no overcurrent protection. The first overcurrent protective device was the person in the chair..... LOL
@@brnmcc01 I would suspect that the 2400V electric chair was fed from a pole transformer connected in reverse, the 120V or 240V connected from the building power (where it can more safely turned on and off) and the 2400V side which normally would have been the primary now fed to the electric chair electrodes.
HI,,,RYAN,question is permit make the raceway inside the transformer in the pads concrete????may i use PVC,i have seen in miami building but im not sure is legal????CASANOVA ELECTRIC CONTRACTOR
Yes, PVC is fine.
Although I have an _”ancient”_ (1976) degree in electrical engineering, I do have one question:
In an area where both 12 Kv and 4 kv distribution systems are used, as a rule of thumb, is one more susceptible than the other to subjecting the end user (120/240v, 1Φ, 3 wire, overhead) to lightning and/or switching surges?
For example, would a lightning strike (direct or indirect) to a 12 kV line get stepped down in voltage more before entering a home than a similar strike to a 4 kV system? Or does lightning not obey the usual mathematics of a transformer’s turns ratio?
Hi Dave. That's a great question, and one that I'm afraid I can't answer. I mainly live in the world of 1kV and lower voltages. Sorry.
Where can you get a straight 240v breaker to buy
Thank you Ryan.. I was always confused about all the different types of systems out there.. I found your channel because I was trying to learn about .. Swimming pool safety.. through Mike Holt videos .. I have learned so much information from the both of you .. Thank you so much
P.S. CAN I ASK A QUESTION ABOUT LOW VOLTAGE POOL LIGHTING TRANSFORMER?
Thanks!
Yes, you certainly can.
@@RyanJacksonElectrical I have a hayward low voltage transformer . 120vac 2amp max ..output 14vac 70 va I have the 70watt junction box kit with transformer.. all plastic..
The instructions say to land the ground wire from feed on ground bar in J box ..but also they state to land bonding grid to this bar as well .. so I will have bonding grid and equipment ground on same bar .. is this ok ??
@@261Pro Perfectly fine.
@@RyanJacksonElectrical Thank you Ryan.. I for some reason was worried about bonding grid and equipment ground of pool panel being together..code saying it is not necessary to bring grid to the panel board.. 680.26 (C) .. and also a healthy fear ...Being a new pool owner is certainly a big responsibility..
Thank you for posting on your channel. The info you share is a goldmine from anyone that is an apprentice all the way up to master. Thank you so much for posting content. I know I am not the only one that appreciates your hard work.
@@dantekester4644 Thank you!
Thanks. This is great info
Excellent explanation. Thank you
I got to the end of this video, disappointed because I didn't see the configuration for which I was searching when I clicked. The configuration I was hoping to see is the one that enters a residence (i.e., 120/240 grounded). Did I miss it?
It's the first system I talk about. 2:50
Excellent presentation!
Single Phase 2W systems are actually very common in North America if you work with Control Transformers, or in a panelshop. Typically in the 100-2000VA size, 600-120V (Canada) and 480V-120V (USA). Great presentation!
Hey Ryan, it seems like the math works the same on the open Delta system using the Pythagorean theorem to get 240v between the two points on the open end.
It’s just a little confusing to me that you can get 240v between the two points on the open ends. And use the math the same way if you were to draw an imaginary line between the two open points. Or am I over thinking it?
If there is a neutral wire on a wye 480/277 secondary, does the wounding has to be grounded ? Can that neutral be floating? And why? Thanks! Very good class.
You're allowed to have an ungrounded 480V wye (but not 208) , but you can not hook up the neutral because any circuit that uses a neutral MUST come from a grounded system. I'm sure there is an obscure application where an ungrounded wye would be useful as opposed to an ungrounded delta, but I'm drawing a blank.
@@RyanJacksonElectricalFor 480v three phase 3wire ungrounded systems you can use 240/480 v transformers wired delta, or 277v transformers wired wye. Because 277/480v three phase 4wire grounded systems are real common, due to having 277v in inventory we just build 480v three phase 3 wire ungrounded ( floated) with them.
remarkable and informative good sir, thank you for taking the time and presenting knowledge in a concise and understandable format for us everyman.
Fantastic video. I learned a lot from this.
Thanks Johnny. I was really happy with this video.
North America, do we use SWER (single wire earth return) from the (single phase) step down pole mounted transformer to the substation?
I see no neutral from the transformer(s) thank you
We use a multi-grounded neutral, which is to say that we have the grounded/neutral conductor that goes from pole to pole and from pole to the customer, and we ground it at every transformer and pole.
@@RyanJacksonElectrical New terminology for me. multi-grounded neutral. pole to pole.
SO, there is no neutral back to the substation. Thank you.
The neutral for the primary is the same neutral being used on the secondary. We call it a common neutral system. The primary bushing is for hot primary conductor and the other end of the winding is attached to case of transformer. As long as the common neutral is attached to the case then the primary winding has two different potential conductors across winding.
The ground SCREWS to the underside of the transformer.
If this should break, is that big trouble?
No, simply because there are tens of thousands of them.
@@RyanJacksonElectrical Question please. Reference the “Multi point grounded
neutral system. (Thousands of them)
Philadelphia area single phase step down transformers I can not
see a NEUTRAL conductor going from pole to pole?
This SHOULD BE in parallel with the MENTIONED multi-point system
which is obvious at every pole?
Thank you.
It’s a common neutral which runs pole to pole at the secondary level. Common meaning same conductor for primary and secondary.
@@bobbrumley3964 Thank you Bob.
Transformers, more than meets the eye.
Every videos helps
Thank You Ryan!!!! Watch your videos every night after work.
Installed a 3 phase & single phase service to a Philly store about 10 years ago. The area still had 2 phase power. Ultility company installed a phase changer then if memory served me right only brought in 5 wires. One conductor was used for the single & 3 phase service. Bad thing about 2 phase if you cross feed wires to a 4 wire 2 phase motor it would only recieve around 180 volts instead of 240 volts burning motor out. At the large hospital/ research centers that I retired from probably had over 200 480 to 120/208 Delta to Wye transformers. They had a few 208 to 240 volt transformers for some small equipment. Thanks for another easy to follow informative vid.
It's actually only around 170 volts if you don't connect the wires right on a 2 phase system. 120v x √2
Thanks Ryan. I have not connected a two phase motor here in Philly since the 1980's. Was in an old machine shop. For fun I did a Google search and could not find any 240 volt 4 pole 4 fuse 30 amp safety switches that I had I stalled a few back in the 1970's for two phase.
On the 3 single phase 4 wire system , the grounding wire coming down the pole from the 3 single pole XMFRs, If that ground wire got cut by a vehicle accident, what would it do to the voltages ?
It really wouldn't do anything, for two reasons. First, and unlike the transformers we install, the utility connects both the primary and the secondary to the frame of the transformer and ultimately to their neutral point. This means there are thousands of those connections throughout the distribution system, so cutting one wouldn't really be problematic. Second, when we measure voltage we usually measure to the metal parts, not to the actual dirt itself. If you cut the wire going to the dirt, but kept the wire connecting the windings to the metal parts, you would still have a predictable voltage from the conductors to the metal parts.
@@RyanJacksonElectrical Good point. Another interesting thing with high leg 120/240 delta systems is, if you lose one of the smaller transformers that doesn't have a center tap, is you don't single phase your motors, everything still will work, like an open leg or ghost leg 240 delta system, you will just have much less KVA capacity until the utility can come and replace the can on the pole, or the HV fuse etc. If you lose a leg on a 208Y120 system, then you get all kinds of strange voltages on your 120v circuits from current backfeeding the dead leg from 208v loads, and 3 phase motors trip on thermal overload, or burn out. Replaced many burned out compressors over the years from that happening where a tree or vehicle accident or other object coming into contact with the POCO distribution lines causing a loss of one phase for awhile.
Geez and I thought I knew everything about transformers
Oh, I don't think any of us really do. ;)
It is truly amazing how much technology has brought to the trade.
I USED to think that I knew practically everything from 30 years in the trade.
Ryan’s channel is my new “go to” place for everything electrical!
He doesn’t have the fancy peanut gallery of experts like Mike Holt, 😉
but he sure does explain things in a straightforward and easy to understand way.
AND....
As Sleepy-Joe Biden would say.....
“C’MON MAN -->>> PUT YOUR DAMN MASK ON !” 😷😆🤣
🇺🇸😥🇺🇸