Control voltage

[controlnovice]

Looking over an Electrical Design specification for a proposed plant in Germany (owner and Engineering oversight in the USA), the MCC low voltage level is 400V, 50Hz, 3 phase.

Smaller loads/motors will be 230V.

The specification indicates that the control voltage (for contactors, etc.) will be 110VAC.

I've seen 220VAC used directly from the 380V bus for motor contactors, but not stepped down to 110VAC.

Is 110VAC common in Europe for control voltage?

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[ScottyUK]

110V AC is very common in the heavier industries (the few the UK has left ) where contactors are simply too big for 24V DC coils to be utilised. Typically a 400/110V isolation transformer is fed from two of the lines. One end of the 110V secondary is bonded to frame earth within the MCC cubicle or withdrawable chassis.

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[jraef]

I'm no expert on Germany, but I have worked for a German company and I don't think so, even though I'd trust that what ScottyUK says is true in the UK. My impression is that they (Germans) would use 220V derived from phase to neutral if 24VDC would not work. For larger contactors they often use small interposing switch devices attached directly to the coils which take the 24VDC control signal and use it to fire the line-neutral for the coil with the hot pulled right off of a contactor line terminal, which would make it 220V.

That said, if your owner company is US based, they may have a valid reason for wanting control schemes to be universally similar across the company facilities, adjusted only for local line power supplies. Don't ASS-U-ME that this is a mistake, it may be a carefully planned compromise. It never hurts to ask (politely) of course.

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[petronila]

Controlnovice,

You are right, in europe 110 V is not a normal Voltage but

I Think is a design matter, due to the Coil voltages could be anyone. Europeans normally use 220 V for control and in USA you could find 110 or 220 Volts, for safety reasons the 110 Volts could be the best choice.

Taking acount your company engineering is from USA they are following the american guidelines.

Regards,

Petronila

 

[ScottyUK]

Thanks jraef - I will keep an eye on anything we get from Germany. Line voltage would be a nasty surprise waiting for the unwary maintenance tech who would be expecting 110V AC or 24V DC on a control circuit.

One more thought: most MCC designs in the UK don't bring the neutral into the starter bucket - switchgear frequently does, but not motor starters. Do the German designs normally have the neutral available? My concern is that it isn't 240V but 415V which is used as a control voltage.

And I thought there was universal harmonisation across Europe... that'll teach me to believe politicians!

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Sometimes I only open my mouth to swap feet...

 

[cbarn24050]

110vac is a very common control voltage on european and american machinery of a certain age, allmost universal before the advent of the PLC.

 

[DaveScott]

In my experience, most large European electrical suppliers, without any specific request, will offer 24V dc as a standard.
110Vac is like flared jeans: out of fashion.

 

[ozmosis]

I would agree with DaveScott, 24Vdc in Germany is probably the most common control voltage. The German development guys in our company always wonder why we specify fully rated (230Vac) relays on our VSD's until we remind them there is a world outside Germany and most of Asia seem quite happy with anything between 110-230Vac.
Darn, are flared jeans out of fashion again?...