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Topic Title: Understanding Split single phase installations.
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Created On: 10 April 2017 11:41 AM
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 11 April 2017 04:34 PM
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Matt01

Posts: 211
Joined: 25 July 2008

this is what i was looking at :- http://www.drivesdirect.co.uk/index.html where they state their kit can convert 480V Split Phase to 415V 3 Phase.

This kit would sit local to the pump set. We do not want to use a generator, when you look at rental costs and fuel costs etc it wouldnt be cheaper.

Edited: 11 April 2017 at 04:40 PM by Matt01
 12 April 2017 12:58 PM
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Delbot321

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Joined: 06 November 2012

On the LV side have you managed to find any manufacturers that can provide circuit breakers that will meet the 460 volt system you will have.

There are a number of urban areas we carry out design work in which still have an REC supply which is a split single phase from years gone by when it was then rated 240-0-240.

All the equipment I've looked at is certified to BSEN numbers which only test it to the 400 volt rating and so 460/480 is outside of these parameters. The result is everything that needs 460/480 distribution is done using switch-fuses with HRC protection and then single phase 230v distribution MCBs downstream.
 12 April 2017 04:15 PM
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di515223

Posts: 337
Joined: 08 July 2010

A couple of points -
What size is each pump? Drives for the pumps will need to be sized accordingly, and will run at less than 100% efficiency, so the energy losses may add up to an unacceptable level.
If all the pumps start simultaneously, is your supply stiff enough? If not, how is this managed?

If the pumps are critical, why can you compromise on the supply? if this supply goes down with no alternative, what happens?

Dave
 14 April 2017 07:40 PM
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mapj1

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There are boards, fuses and switches rated for 690V of course, from the more up-market makers like Siemens and Hagar, and actually the phase to neutral or ground voltage is the same as it would be in any normal 3phase system - its only the phase to phase voltage that is a 25% higher, so the real risk of using 400v rated kit is not high, more of problem of a lack of certification.

-------------------------
regards Mike
 15 April 2017 01:12 PM
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perspicacious

Posts: 7854
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Sure, 460V equipment can be connected between lines (provided it doesn't require an earthed N for any reason), but such equipment is pretty rare.

A lot of 3hp and above single phase motors used on farms were supplied wound ready for 240/480 V.

Regards

BOD
 15 April 2017 03:06 PM
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kellyselectric

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Joined: 22 July 2016

I'm surprised they still install this type of supply I thought that the idea of having non standard voltages was a thing of the past. That said there's a farm near hear which is around 5 miles from our 400/132/33 KV sub and only about half a mile from a standard ,11Kv 3 phase line that has this system installed been that way for years I think I really thought this arrangement was an old fashioned system that was being done away with.
 15 April 2017 05:28 PM
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mapj1

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well, its a nice way of beefing up a single phase supply, and cheap in terms of the overhead lines.
If you don't need 3 phases, and only have single phase loads, its a good system and to a degree helps with voltage drops.

-------------------------
regards Mike
 17 April 2017 04:47 PM
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ArthurHall

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Are you sure the DNO said a 220kVa supply? That would be very unusual at single phase. Did they not mean 2x20kVa. All the split phase transformers I have seen had two LV windings that could be wired in series to give 250/0/250 or wired in parallel to give one 250V supply but with twice the kVa.
Traditionaly farms would have one 500V motor which would be used to drive various bits of plant at different times of the year. As few farms have 500V motors it is unusual for a DNO offer a split phase supply, even if they are reusing a split phase transformer it would be normal to connect it to give a single 250V supply.
 18 April 2017 11:08 AM
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Matt01

Posts: 211
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The DNO supply is a 220kVA split phase supply definitely it's on the DNO quote and i have confirmed this on a phone call.

Do any of you know a manufacturer that can help me with with a panel board rated at 480V?? Schneider MCCBs are rated at this, but the busbar in the panel isn't.

Pumps are 4 x 3ph 400V 5kW.
 18 April 2017 11:29 AM
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Matt01

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Hager do not make any panel boards that are rated past 415V......I have just spoken to their technical team.
 18 April 2017 12:18 PM
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OMS

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Any switchgear manufacturer making equipment compliant with BS EN 61439 will be able to provide you with nominal 500V switchgear

Basically they need to verify creepage and clearance distances for the elevated voltage and agree with you the value of the dielectric tests for impulse withstand (Table 1 and 2 of the standard from memory, but there are switchgear builders on here who can confirm that)

I'm presuming that you want a single switchboard to accept the 220KVA supply and from that distribute a combination of Phase L1 and Phase L2 to neutral loads (ie 250V single phase) and a number of two phase loads (ie 500V gear)

Please check, but I'm pretty sure the MEM Glasgow equipment carried a 500V rating for the peripheral stuff - or try Kraus & Naimer Limited - I've no connection with either company

The intake switchboard is down to whichever switchgear company you fancy - I could suggest a few - where are you based ?

Regards

OMS

Regards

-------------------------
Let the wind blow you, across a big floor.
 18 April 2017 03:32 PM
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di515223

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I may be missing something here, but why do you need a 220kVa supply for 4 off 5 kW Motors?I would suggest for 20kW worth of motors, a 230V single phase supply would be practicable as the inverters could control the start current and a bit of sequencing could limit your fusing to about 120A or thereabouts.

Dave
 18 April 2017 04:42 PM
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Matt01

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I want a panel board than can connect from the DNO's ISU. The idea is to bring the L1 phase and L2 phase into a suitably rated panelboard (ignore the L3 phase as it does not exist) and distribute around the site accordingly. Some outgoing supplies are just single phase and some a 2 phase with the use of a digital convertor to make them 3ph 400V local to the equipment.

I don't seem to having a problem with MCCB's that are rated up to 660V it's the busbar rating of the panel boards themselves. The majority of the manufacturers only test them up to 415V not 480V. To get the certification on a panel board for this is ridiculously expensive, i just want an off the shelf panel that's suitably rated.

Looks like GE A-Series* II Panelboard are rated at 480V
 18 April 2017 06:29 PM
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alancapon

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Originally posted by: Matt01
. . . I don't seem to having a problem with MCCB's that are rated up to 660V it's the busbar rating of the panel boards themselves. The majority of the manufacturers only test them up to 415V not 480V. To get the certification on a panel board for this is ridiculously expensive, i just want an off the shelf panel that's suitably rated. . .

Remembering of course that the maximum working phase-to-phase voltage allowed on a two-phase or split-phase installation is actually 506V.

Regards,

Alan.
 18 April 2017 08:06 PM
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mapj1

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Ah, but that is not the nominal voltage which is what everyone quotes. - the 10% variation applies in the same way to 400V rated kit, which may be exposed to 440V during the upper bounds of perfectly normal operation. Well, just about.normal.

There may be some merit then in looking at manufacturers who supply gear made for 400/690 , or American 480V . I'm a bit surprised by Hagar I admit, I'm sure they used to, perhaps the bus-bar design has changed.

-------------------------
regards Mike
 18 April 2017 09:58 PM
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OMS

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Switchgear design accounts for the upper bound based on the declared nominal which in this case is at least 460V

The thinking here is alles uber den platz - a 3 phase board has 33% more copper than required. Unless the OP can find a COTS 680V going cheap and doesn't need a particularly high form of seperation then the local tin bashed and copper benders could build a BS EN switchboard for modest cost - particularly as it only needs a few 100A outputs and then most of the next tier is single phase kit or is 500V two phase feeding the motor converters which again is of modest ampacity

OMS

-------------------------
Let the wind blow you, across a big floor.

Edited: 18 April 2017 at 10:05 PM by OMS
 19 April 2017 09:55 AM
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Matt01

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Realistically though i would like an off the shelf panel board. I didn't think this would as hard to source.
 19 April 2017 10:36 AM
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OMS

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OK - I've copied this bit from BE EN 61439 for you so you can at least have the conversations with potential suppliers

5.2 Voltage ratings
5.2.1 Rated voltage (Un) (of the ASSEMBLY)
The rated voltage shall be at least equal to the nominal voltage of the electrical system.
5.2.2 Rated operational voltage (Ue) (of a circuit of an ASSEMBLY)
The rated operational voltage of any circuit shall not be less than the nominal voltage of the electrical system to which it is to be connected.
If different from the rated voltage of the ASSEMBLY, the appropriate rated operational voltage of the circuit shall be stated.
5.2.3 Rated insulation voltage (Ui) (of a circuit of an ASSEMBLY)
The rated insulation voltage of a circuit of an ASSEMBLY is the voltage value to which dielectric test voltages and creepage distances are referred.
The rated insulation voltage of a circuit shall be equal or higher than the values stated for Un and for Ue for the same circuit.
NOTE For single-phase circuits derived from IT systems (see IEC 60364-5-52), the rated insulation voltage should be at least equal to the voltage between phases of the supply.
5.2.4 Rated impulse withstand voltage (Uimp) (of the ASSEMBLY)
The rated impulse withstand voltage shall be equal to or higher than the values stated for the transient overvoltages occurring in the electrical system(s) to which the circuit is designed to be connected.

Uimp in this application would be 8kV but is typically 6kV for origin switchgear of conventional 415 systems

Based on what you know about the voltage presented to you and how you want to provide a front end switchboard then you need a panel board that meets each of the above criteria

So - what is the nominal voltage (for rating), the operational voltage, the insulation voltage and impulse voltage required.

It is likely that you can select a COTS piece of equipment if it has applications in say the US or parts of the middle east - for MCCB's and switchfuses, they almost certainly have a 690V rating as standard - so it's basically the main busbar and risers you are concerned about

Equally, for modest cost you could have a small switchboard assembly that has exactly what you want and a bit of paper to say it's compliant with BS EN 61439 (and the LV directive etc via CE marking)

I suspect if you talk to the technical people at various switchgear companies their current standard offerings may well be suitable - but equally they may well not have test certs to demonstrate that - but may well test for you at a small additional cost.

Basically, we are playing with numbers here - the physical arrangements of the board will most probably not change (as the voltage variations in question are "small") - but I'm not a switchgear builder, only they can answer this question

I've no idea what this site is, but a small switchboard at the origin will only be a fraction of the total installation cost (as you can select "conventional kit" from that Tier down)


Regards

OMS

-------------------------
Let the wind blow you, across a big floor.
 20 April 2017 08:35 PM
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perspicacious

Posts: 7854
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The DNO supply is a 220kVA split phase supply definitely it's on the DNO quote and i have confirmed this on a phone call.
Do any of you know a manufacturer that can help me with with a panel board rated at 480V?? Schneider MCCBs are rated at this, but the busbar in the panel isn't.
Pumps are 4 x 3ph 400V 5kW.



I may be missing something here, but why do you need a 220kVa supply for 4 off 5 kW Motors?I would suggest for 20kW worth of motors, a 230V single phase supply would be practicable as the inverters could control the start current and a bit of sequencing could limit your fusing to about 120A or thereabouts. Dave

Me too. Where's the rest of the demand?

Regards

BOD
 21 April 2017 11:58 AM
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JohnRRussell

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Originally posted by: Matt01

I want a panel board than can connect from the DNO's ISU. The idea is to bring the L1 phase and L2 phase into a suitably rated panelboard (ignore the L3 phase as it does not exist) and distribute around the site accordingly.


I don't see why you can't use a standard 415V 3-phase board. Standard 3-phase equipment is rated for 240V to earth, 415V between phases. 415V between phases means in reality 415V between L1-L2, and 415V between L2-L3. So insulation withstand between L1-L3 will be 830V in reality for conventional flat formation busbars and switches (and it's a long time since I've seen triangular formation busbars at LV). If you use L1 and L3 (not your suggestion of L1 and L2) then you're fine.

Where we need the full 240-0-240V single split-phase, at transformers and generators before it breaks out to conventional 240V single-phase supplies, we use L1 and L3 for 240V and the neutral on L2.

The 220kVA supply is odd. The largest single split-phase transformer recognised by EA-TS-35-1 standard for distribution transformers is 100kVA. Which isn't to say that bigger isn't possible, just that it would be very unusual for a DNO to use it. When we need bigger than 100kVA we have to take an HV single-phase supply and buy our own transformer.
IET » Wiring and the regulations » Understanding Split single phase installations.

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