3 phase wiring not using high leg question

[pgoldston]

I have a dynocom dyno currently wired as per the below wiring diagram in single phase 240v. The dyno works just fine, but per the diagram it could potentially have 30% more holding power if I wire it in 3 phase. The diagram states that it can be wired as 3 phase but use the high leg. Theres only 2 wires to connect to.

If I have 3 phase power how to I confirm the high leg and wire this correctly? I greatly appreciate any help with this.

 

[sparky 1971]

The link won't open.

 

[pgoldston]

Screenshot add the initial post

 

[BillK]

I'm confused. If you want to wire it three phase I would think you need to use all three phases. I think when they say not to use the high leg they are referring to wiring it for single phase only. I would get in touch with Dynocom to verify. There might be a different wiring diagram for three phase. I dont see anything on their web site as far as wiring diagrams. One of my customers has a hub dyno but I dont think it is Dynocom.

 

[micromind]

A 240 volt 3 phase system that has a neutral will also have a high leg. That's basic physics, there's no way around it. It will have 240 from any phase to any other phase, 2 of the phases will be 120 to neutral and the high leg will be 208 to neutral.

A 3 phase system that has a neutral but no high leg will have 120 from any phase to neutral but only 208 from any phase to any other phase. Basic physics again.

The instructions say to not use the high leg. That means that the only possible way to connect it for 240 is by using the 2 120 to neutral phases, just like you have it.

I'm pretty sure the instructions were written by an engineer with a poor understanding of electrical systems in general and an ever poorer understanding of this machine.

 

[sparky 1971]

I have a dynocom dyno currently wired as per the below wiring diagram in single phase 240v. The dyno works just fine, but per the diagram it could potentially have 30% more holding power if I wire it in 3 phase.

It says that, but I don't see a way on that diagram. That diagram *****. Is there anything else, paperwork wise?

The diagram states that it can be wired as 3 phase but use the high leg. Theres only 2 wires to connect to.

It says not to use the high leg, so if you have a 240 three phase system, you have to wire it single phase. It might be able to be three phase if you have 208?

If I have 3 phase power how to I confirm the high leg and wire this correctly? I greatly appreciate any help with this.

You first have to see if you even have three phase power available. There should be a label on the panel. If you do have it, it's probably 208, but could be 240 with a high leg. Start by seeing if you even have three phase. Is this dyno at your house or a commercial building? If it's your house, you might as well stop there as you don't have three phase power.

 

[Chuckster in NJ]

TIP! Call a professional……… Your loss may be more than just financial.

 

[fitter30]

Two legs of three phase is single phase. Makes no sense.
480vac 4 wire wye
277vac any hot to neutral
480 between any two hots
480 delta 480 any two legs/ B leg grounded

 

[nadogail]

A volt meter will show you the "High Leg". just measure the voltage of each leg in relation to the Neutral, the "High Leg" will be higher than the other two; two legs should be about the same voltage in relation to Neutral and the other Leg should be noticeably higher.

When you do identify the High Leg, sometimes called the "Wild Leg" my personal Standard Practice is to identify it with Orange Tape.

 

[walta]

“2 LEGS OF THE 3-PHASE 240 VAC RECOMMENED (DO NOT USE HIGH LEG)”

If you happen to have high leg 3 phase you could use it to power the machine if you connected it 3 phase or you could connect the machine single phase between A and C but do not connect the machine to the B leg in single phase.

It is very unlikely your 3-phase service has a high leg as it is pretty rare It is much more likely to have 208 3-phase. If you have 208 and need the extra holding power consider adding boost transformers and get the machines power up over 240V without going over the 300V limit.


Walta

 

[pgoldston]

Pretty much everyone is saying what I have thought at 1 time or another. I was highly confused about the way that it is written. What it really seems like is not so much "3phase" power is needed to get max holding power, rather just a higher voltage, ie L1 and L2 being 208/240v each versus 120v each as I currently having it wired.

 

[Norcal]

How rare 240/120V 3Ø is depends where you are, here PG&E loves it for AG services.

 

[wyliesdiesels]

I have a dynocom dyno currently wired as per the below wiring diagram in single phase 240v. The dyno works just fine, but per the diagram it could potentially have 30% more holding power if I wire it in 3 phase.

i dont see where on the diagram it says to use 3 phase. all i see is single phase connected to a 3 phase system which makes no sense

The diagram states that it can be wired as 3 phase but use the high leg. Theres only 2 wires to connect to.

it says DONT use the high leg. may want to edit your post

If I have 3 phase power how do I confirm the high leg and wire this correctly? I greatly appreciate any help with this.

easy. hi leg is 208v line to neutral. so to determine which out of the 3 phase legs is the high leg, just meter from each leg to neutral. 2 should be 120v. the third should be 208v

 

[alfredeneuman]

Two legs of three phase is single phase. Makes no sense.
480vac 4 wire wye
277vac any hot to neutral
480 between any two hots
480 delta 480 any two legs/ B leg grounded

But it's not 480vac and not wye connected. No legs are grounded.
It's a center tapped 4 wire 240V Delta system, unlike any other system.

 

[fitter30]

But it's not 480vac and not wye connected. No legs are grounded.
It's a center tapped 4 wire 240V Delta system, unlike any other system.

Then use a buck boost transformer so you could get 277v

 

[walta]

i dont see where on the diagram it says to use 3 phase. all i see is single phase connected to a 3 phase system which makes no sense

“(3-PHASE OR SINGLE PHASE)

DO NOT EXCEED 300VAC MAX!”

Walta

 

[firebirdparts]

.....

 

[dave*99]

Seems this very poorly worded diagram is attempting to say the Dyno requires single phase 240V supply.

It further attempts to describe how to connect the Dyno when fed from a 3 phase panel. I don’t think the Dyno actually can use all 3 phases.

The author probably knows there are different types of 3 phase power systems but can’t describe all the possibilities.

Perhaps they mean to use 2 legs of the available 3 phase power and not to grab one phase and a neutral. And don’t use the high leg either.

As for the potential 30% reduction in torque holding…… dunno.

 

[micromind]

It's possible that the 30% thing is whether it is connected to 2 legs of a 208 system vs. actual 240 from a single phase system or the two 120 volt legs of a 240 ∆.

 

[wyliesdiesels]

Two legs of three phase is single phase. Makes no sense.
480vac 4 wire wye
277vac any hot to neutral
480 between any two hots
480 delta 480 any two legs/ B leg grounded

That isnt the only 3 phase system voltage out there.

 

[wyliesdiesels]

“2 LEGS OF THE 3-PHASE 240 VAC RECOMMENED (DO NOT USE HIGH LEG)”

If you happen to have high leg 3 phase you could use it to power the machine if you connected it 3 phase or you could connect the machine single phase between A and C but do not connect the machine to the B leg in single phase.

It is very unlikely your 3-phase service has a high leg as it is pretty rare It is much more likely to have 208 3-phase. If you have 208 and need the extra holding power consider adding boost transformers and get the machines power up over 240V without going over the 300V limit.


Walta

Not true in the US. Tons of Delta connected hi-leg services here.

 

[wyliesdiesels]

Then use a buck boost transformer so you could get 277v

Not needed

 

[wyliesdiesels]

Seems this very poorly worded diagram is attempting to say the Dyno requires single phase 240V supply.

It further attempts to describe how to connect the Dyno when fed from a 3 phase panel. I don’t think the Dyno actually can use all 3 phases.

The author probably knows there are different types of 3 phase power systems but can’t describe all the possibilities.

Perhaps they mean to use 2 legs of the available 3 phase power and not to grab one phase and a neutral. And don’t use the high leg either.

As for the potential 30% reduction in torque holding…… dunno.

The controls probably operate on 120v off one of the ungrounded input legs. So if you connect 2 legs, one being the hi-leg, to the machine and it happens to be the one powering the controls, the magic smoke will get let out (208v line to neutral).

 

[nadogail]

In my experience in San Diego and Imperial counties of California, I have encountered both Star and Delta connected 3 Phase services.

I learned to check after I had assumed that all the buildings were Star connected. Star and Wye connections look the same to me.

 

[wyliesdiesels]

In my experience in San Diego and Imperial counties of California, I have encountered both Star and Delta connected 3 Phase services.

I learned to check after I had assumed that all the buildings were Star connected. Star and Wye connections look the same to me.

They are the same… or did you mean delta and wye?

 

[nadogail]

They are the same… or did you mean delta and wye?

No, I know that Star, also known as Wye, is the same.

Delta with a Corner Ground has a Wild Leg.

 

[wyliesdiesels]

No, I know that Star, also known as Wye, is the same.

Delta with a Corner Ground has a Wild Leg.

No it doesnt. Hi-leg/wild-leg is only found on center tapped delta connected banks. A corner grounded delta doesnt even have a neutral(its 3-wire) so there would be no way to get a wild leg. Furthermore, voltage to ground is 240v or 480v on only 2 legs. The third grounded leg is obviously 0v to ground.

 

[nadogail]

No it doesnt. Hi-leg/wild-leg is only found on center tapped delta connected banks. A corner grounded delta doesnt even have a neutral(its 3-wire) so there would be no way to get a wild leg. Furthermore, voltage to ground is 240v or 480v on only 2 legs. The third grounded leg is obviously 0v to ground.

Thank You for the informative correction.

 

[dave*99]

The controls probably operate on 120v off one of the ungrounded input legs. So if you connect 2 legs, one being the hi-leg, to the machine and it happens to be the one powering the controls, the magic smoke will get let out (208v line to neutral).

But if that were true wouldn’t the control current then be on the ground wire?

The first line states HBL2623 which is a 3 wire L6-30R. So it seems this text it telling you the options to power that receptacle.

The entire goal is to get 240V across the X and Y terminals of that receptacle.

If you are connecting to a 3 phase panel it very unclearly describes some options. The 240V goal is hidden in the poor wording as the writer can't clearly address all the possible implementations of 3 phase power that the user may encounter.

If also seems you can cause a 30% reduction in holding power if you do something wrong. That something as another poster said, may be to only put 208V across X and Y.

With only 3 wires the machine will not have access to anything other than (X to Y) and (X or Y) to ground voltage. So if controls were powered from one terminal the only return paths are the other terminal and ground.

 

[wyliesdiesels]

But if that were true wouldn’t the control current then be on the ground wire?

The first line states HBL2623 which is a 3 wire L6-30R. So it seems this text it telling you the options to power that receptacle.

The entire goal is to get 240V across the X and Y terminals of that receptacle.

If you are connecting to a 3 phase panel it very unclearly describes some options. The 240V goal is hidden in the poor wording as the writer can't clearly address all the possible implementations of 3 phase power that the user may encounter.

If also seems you can cause a 30% reduction in holding power if you do something wrong. That something as another poster said, may be to only put 208V across X and Y.

With only 3 wires the machine will not have access to anything other than (X to Y) and (X or Y) to ground voltage. So if controls were powered from one terminal the only return paths are the other terminal and ground.

as bad as that is, it wouldnt surprise me if thats how it was wired. hi-leg to ground is the same voltage as hi-leg to neutral so the magic smoke can still be let out if one is not paying attention

 

[alfredeneuman]

Star and Wye connections look the same to me.

The high leg is the "B" phase, and required to be marked orange, except in San Francisco, where it's marked violet. (I'm surprised it's not pink or brown)

 

[sparky 1971]

The high leg is the "B" phase, and required to be marked orange, except in San Francisco, where it's marked violet. (I'm surprised it's not pink or brown)

Is there a reason for that? The only thing I can think of is to keep someone from thinking it's 480 but the lack of a brown or yellow would satisfy my curiosity.

 

[dave*99]

as bad as that is, it wouldnt surprise me if thats how it was wired. hi-leg to ground is the same voltage as hi-leg to neutral so the magic smoke can still be let out if one is not paying attention

One option in the callouts says X to 240 and Y to neutral. So the controls must run on 240.

 

[alfredeneuman]

Is there a reason for that? The only thing I can think of is to keep someone from thinking it's 480 but the lack of a brown or yellow would satisfy my curiosity.

Bingo! (Although pink is not a 480 color and would be more suitable to SF)

 

[Norcal]

Bingo! (Although pink is not a 480 color and would be more suitable to SF)

I thought SF's 480V color code was Brown, Purple, Yellow, assumed because the NEC requires orange for the 240V high leg.

 

[alfredeneuman]

I thought SF's 480V color code was Brown, Purple, Yellow, assumed because the NEC requires orange for the 240V high leg.

SF Code>>>
110.15 High-Leg Marking. On a 4-wire, delta-connected system where the midpoint of one phase winding is grounded, only the conductor or busbar having the higher phase voltage to ground shall be durably and permanently marked by an outer finish that is purple in color or by other effective means. Such identification shall be placed at each point on the system where a connection is made if the grounded conductor is also present.