Rotory Phase Converter

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iwire

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Massachusetts
Correct. but the output conductors need 150 amp OCPD if they are going to be 150 amp conductors.

I am not as sure as that as you seem to be.:)


The point of reduction to that OCD is a feeder tap. Two lines are effectively direct connected to the input in such a converter, so at very least you have on those two lines the equivalent of a 150 amp conductor directly tapped to one with 225 amps overcurrent protection. The "manufactured" phase may be somewhat inherently protected from overload just by the impedance of the converter - but NEC likely wouldn't recognize that as proper protection anyway.

Not having done rotary phase converters would I be correct in saying that you only supply three phase loads with them?
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
I would tend to agree. Without additional information one could not confirm that the connection shown is "listed as grounding or bonding equipment"... my guess would be that it is but that is an unqualified assumption.
I see similar installs often where the electrician uses neutral/grounding bars such as the ones in panelboard cabinets.
I may be making a mistake, but if it's good enough for panelboard neutral./grounding connections, I tend to approve it.

If so inclined, take a look at NEC ROP 5-120 Log #2506 NEC-P05. This explains that it must be a 1/4" X 2 busbar X required length and not a ground bar or similar such as pictured in the OP. This change was made to make clear that the installation as shown in the picture by the OP is not compliant. Also, the IAEI 2014 Analysis of Changes points this out as well on page 94.
 

kwired

Electron manager
Location
NE Nebraska
I am not as sure as that as you seem to be.:)




Not having done rotary phase converters would I be correct in saying that you only supply three phase loads with them?

My experience with them is mostly for center pivot irrigation machines. They are typically supplied with a 30 amp or less 480 volt three phase feeder. Often times the input to the unit is 30 amps and output is going to hit an overcurrent device on the machine so the load side overurrent is there whether needed or not. But I see it as no different then a feeder tap.

If you are not familiar with the design of such units - when you wire up a smaller unit like there is on the irrigation machines - incoming L1 and L2, are directly tied to outgoing L1 and L2 as well as some leads to the converter. Outgoing L3 is derived in the converter.

Any single phase load on load side needs to be tied to L1 and L2 - they are the same thing as they are on the input side. On the irrigation machines the single phase load is usually just a 480x120 control transformer, but you will not normally get 480 on the manufacture phase, not a stead reliable 480 anyway, but enough phase shift a three phase motor will have necessary torque to operate. These are not a good source for just any application, and motors may even need to be oversized in some instances from what they would be on a true three phase supply.
 

augie47

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Tennessee
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State Electrical Inspector (Retired)
If so inclined, take a look at NEC ROP 5-120 Log #2506 NEC-P05. This explains that it must be a 1/4" X 2 busbar X required length and not a ground bar or similar such as pictured in the OP. This change was made to make clear that the installation as shown in the picture by the OP is not compliant. Also, the IAEI 2014 Analysis of Changes points this out as well on page 94.

This may be a situation where you and I will just have to continue to disagree.
I have read the ROP and see the change to the buss bar requirement WHEN USED but the use of a listed grounding equipment still remains an option.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
This may be a situation where you and I will just have to continue to disagree.
I have read the ROP and see the change to the buss bar requirement WHEN USED but the use of a listed grounding equipment still remains an option.

I'm not sure we disagree or not. I'm not saying that you must use 250.64(D)(1)(3) if you have multiple disconnects. One could run an unspliced GEC to the first disco. and use a split bolt from that GEC to go to another disco.per 250.64(D)(1)(2). What I am saying is that if you elect to use the option in 250.64(D)(1)(3) it must be a busbar 1/4" thick X 2" wide X required length for the number of connections. For example, the typical intersystem bonding bar used to comply with 250.94 could not be used to comply with 250.64(D)(1)(3).
 

cadpoint

Senior Member
Location
Durham, NC
OK Texie; OK Augie47, It looks to me that they took the guts out of a can and slapped it
on wood? I thought that if this type of installation was to happen that is it needs to have
isolation bushing, to raise this off application off the wood?

I'll admit, I didn't read any article listed.

Either care to comment?
 

kwired

Electron manager
Location
NE Nebraska
I'm not sure we disagree or not. I'm not saying that you must use 250.64(D)(1)(3) if you have multiple disconnects. One could run an unspliced GEC to the first disco. and use a split bolt from that GEC to go to another disco.per 250.64(D)(1)(2). What I am saying is that if you elect to use the option in 250.64(D)(1)(3) it must be a busbar 1/4" thick X 2" wide X required length for the number of connections. For example, the typical intersystem bonding bar used to comply with 250.94 could not be used to comply with 250.64(D)(1)(3).
The OP is not using the (D)(1)(3) option he is using the (D)(1)(2) option, next question is whether it is listed for the grounding and bonding.

OK Texie; OK Augie47, It looks to me that they took the guts out of a can and slapped it
on wood? I thought that if this type of installation was to happen that is it needs to have
isolation bushing, to raise this off application off the wood?

I'll admit, I didn't read any article listed.

Either care to comment?
Why would it need to be isolated from wood?:?

I would say if it were bolted to building steel it could even serve as the method of bonding the building steel.



If the item pictured in OP is permitted as is - I also don't see why it can not serve as the required intersystem bonding terminal as well.
 

Besoeker

Senior Member
Location
UK
The inspector is wrong. If you have 150 amps @240, 3 phase on the secondary that is roughly 60 KVA. Well, you have to input at least 60 KVA of power
kVA isn't power. Power is kW or kVA times PF.
The input and output power factors could be different.
 

jtinge

Senior Member
Location
Hampton, VA
Occupation
Sr. Elec. Engr
kVA isn't power. Power is kW or kVA times PF.
The input and output power factors could be different.

Power and KVA analogy:

Beer factor (pf) = Volume of beer (kW)/Volume of mug (kVA)

Mug (KVA) has to hold both beer and foam.

If you reduce your foam, the mug can hold more beer, and your can drive your beer factor towards 1.0.

I'll let you extend this line of thought to explain why equipment has to be sized larger for loads with poor power factors.
 

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GoldDigger

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Location
Placerville, CA, USA
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Retired PV System Designer
Love the analogy! :thumbsup:
Now figure out how to get the motor efficiency into the picture.
Maybe the outside volume of the glass?
Outside volume to inside volume --> PF, beer to foam --> efficiency?
 
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texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
kVA isn't power. Power is kW or kVA times PF.
The input and output power factors could be different.

Oh the sharp eye of the Brit.:) Of course KVA is not power. In an effort not to use the term KW precisely because of unknown PF I slipped and used the term power along with it. My bad.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
The OP is not using the (D)(1)(3) option he is using the (D)(1)(2) option, next question is whether it is listed for the grounding and bonding.

Why would it need to be isolated from wood?:?

I would say if it were bolted to building steel it could even serve as the method of bonding the building steel.



If the item pictured in OP is permitted as is - I also don't see why it can not serve as the required intersystem bonding terminal as well.

The OP is not using the (D)(1)(2) option. That would be such as a tap using a split bolt or a compression connector, etc. What he has is not a connector listed for grounding and bonding. In my view the OP is clearly (D)(1)(3) and it must be a 1/4" X 2" X xxxx busbar.
Somehow I'm going to convince you guys...I know it's petty, but somehow this has struck nerve with me.:)
 

kwired

Electron manager
Location
NE Nebraska
The OP is not using the (D)(1)(2) option. That would be such as a tap using a split bolt or a compression connector, etc. What he has is not a connector listed for grounding and bonding. In my view the OP is clearly (D)(1)(3) and it must be a 1/4" X 2" X xxxx busbar.
Somehow I'm going to convince you guys...I know it's petty, but somehow this has struck nerve with me.:)
There are multiple port conectors, why couldn't this device be considered one of those? I feel it comes closer to that description then a bus bar. You attach the "connection devices" to a bus bar. (D)(1)(3) even seems to look at it that way by stating: "Connections shall be made by a listed connector or by the exothermic welding process." Meaning you need to add the connection device to the bus bar.

Without knowing the model number of what is pictured I will not claim it is or is not listed for grounding and bonding, but still think by design it utilizes (D)(1)(2) instead of (D)(1)(3). JMO.

I can't imagine a "neutral assembly" designed for a panelboard - especially one suitable for use as service equipment wouldn't be listed for grounding and bonding, but I may buy into it only being listed when installed within a panelboard it was tested with.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
There are multiple port conectors, why couldn't this device be considered one of those? I feel it comes closer to that description then a bus bar. You attach the "connection devices" to a bus bar. (D)(1)(3) even seems to look at it that way by stating: "Connections shall be made by a listed connector or by the exothermic welding process." Meaning you need to add the connection device to the bus bar.

Without knowing the model number of what is pictured I will not claim it is or is not listed for grounding and bonding, but still think by design it utilizes (D)(1)(2) instead of (D)(1)(3). JMO.

I can't imagine a "neutral assembly" designed for a panelboard - especially one suitable for use as service equipment wouldn't be listed for grounding and bonding, but I may buy into it only being listed when installed within a panelboard it was tested with.

I think the difference is that (D)(1)(2) could be used in a tap situation but that would require connecting directly to the GEC. If you use (D)(1)(3) with the busbar the gives you the ability to stop the GEC at that point and run taps and/or bonding jumpers where ever needed. In other words it acts as a central connection point.
FWIW we had quite a discussion about this at a meeting attended by NEMA, NFPA and UL representatives and this was their view. In fact they maintain that the busbar option was reworded in the 2014 to make clear that it has to be a busbar of the cited dimensions. Under the old wording it was possible to use something like in the OP as it likely met the 1/4" and 2" dimensions the way it was worded. Note the new language makes it clear that it is 1/4" THICK X 2" WIDE X length required.
I'm doing my best to convince you guys.:)
 

kwired

Electron manager
Location
NE Nebraska
I think the difference is that (D)(1)(2) could be used in a tap situation but that would require connecting directly to the GEC. If you use (D)(1)(3) with the busbar the gives you the ability to stop the GEC at that point and run taps and/or bonding jumpers where ever needed. In other words it acts as a central connection point.
FWIW we had quite a discussion about this at a meeting attended by NEMA, NFPA and UL representatives and this was their view. In fact they maintain that the busbar option was reworded in the 2014 to make clear that it has to be a busbar of the cited dimensions. Under the old wording it was possible to use something like in the OP as it likely met the 1/4" and 2" dimensions the way it was worded. Note the new language makes it clear that it is 1/4" THICK X 2" WIDE X length required.
I'm doing my best to convince you guys.:)
And I am doing my best to convince you that I don't believe the item in question is a "bus bar" but rather a "multiple port" terminal. If anything it needs to be attached to the required "bus bar", just like any other terminal used to land a conductor on the bus bar.

Without reading any ROP's I don't know what the intent was though, but IMO if the intent was to eliminate the type of install we are questioning, they have more work to do on wording.
 

Besoeker

Senior Member
Location
UK
I'll let you extend this line of thought to explain why equipment has to be sized larger for loads with poor power factors.
OK.
Let's take the case of a fixed power (kW) at different power factors.
PF = kW/kVA
That's just the basic real power/apparent power definition.

From that:

kW = PF * kVA

Lower PF and you have to increase A for the same kW.
More A, bigger conductors, bigger switchgear.
 
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