690VAC 3 phase power?

[hltc]

Have a project where they are stating they have 690VAC/50/3

I believe the location is Madagascar but what I've found is they use 380VAC or 230VAC.

690 seems like an odd voltage for 3 phase motors, and even worse finding a control transformer that can give me 115VAC for the PLC.

Has anyone run into this voltage before?

 

[wayne440]

http://www.dbp.org.uk/cs/DBP00081.pdf

Here is a brief about the reasoning.

 

[hltc]

I pretty much figured the reason behind it was lower current demand at the higher voltage. I just hate to be stuck with a custom transformer on this

 

[waross]

I understand that 690 V is derived from 400 V transformers or windings connected in star. It may be easier to locate a 400:115 v transformer, or 400:24 and go with a 24 V PLC.

Bill
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"Why not the best?"
Jimmy Carter

 

[ScottyUK]

It's becoming increasingly common in Europe as an intermediate voltage for applications which are too big for the 400V LV system, but which are still small enough to allow the costs of a 3.3kV or 6.6kV system (or equivalent) to be avoided. 690V is 'low voltage' - once you make the jump to 'high voltage' the complexity of the rules and regulations increase significantly, so if HV can be avoided then the easier for the operator.

It's certainly not a 'custom' transformer, nor custom motors.


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If we learn from our mistakes I'm getting a great education!

 

[jraef]

If you are in the US, you will not find any 690VAC control transformers as this falls outside of the scope of the NEC and UL/NRTL testing authority, which defines anything over 600V as medium Voltage. So the only possible source would be IEC transformers and with no market for them it's unlikely anyone will have them in stock.

But I also think you may want to re-think your decision to use 115VAC input to your PLC, or for anything else in your panel for that matter. NOBODY in Madagascar, or anywhere else in that region, is going to be able to procure any 115V replacement parts, coils, breakers etc. The much much more commonly accepted control voltage strategy worldwide like this would be 24VDC. You can easily find 24VDC power supplies that will accept 690VAC input. But also check the configuration of the supply system because waross is right, 690VAC is almost always Wye (Star) meaning it's really 400Y690V, so to feed a power supply it would be better to use 400V by connecting Line and Neutral.

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[Skogsgurra]

There's a small complication. A 690 V grid is always an IT grid. There's no Neutral available, so you need to use the 690 V.

Jeff's comment about control voltage is correct. But, there are also 220/230 V AC coils used. For larger contactors and for breakers, 220/230 V is very common.


Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[hltc]

Very good idea about using 24VDC for the control system. I generally do not do this, as DC tends to pick up more noise as alot of contractors tend to run the control signals (limit switches, etc) from the field in the same conduit as the motor power. I'll just spec in the drawings they must be run independent of the motor power.

 

[rasevskii]

I believe that 690V 3ph AC is a commonly used standard for wind farms generators. Also the running of 24VDC circuits in the same conduits or cable trays as main power conductors is not allowed or can be a code violation in many locations. Separate conduits or trays have to be run instead. The LV DC cables should also be screened with the screens earthed at only one point (such as at the control room) to avoid stray currents flowing in the screens and the resulting electrical interference.

This is common practice since electronics were introduced in power station environments decades ago. I mean from the days of analog electronics such as excitation systems and turbine governors.

rasevskii

 

[MAGTiger]

Yes, we are seeing more specifications for this voltage and it is challenging when a customer wants UL listing with 690v as there are no 690v terminal blocks that are UL listed. Thus, it can become an expensive solution for products at current ratings that are more competitive with term blocks. We quote a lot of business in Australia at 690v.

Neil