Low Mains In Spain

[fincaman]

Hello All, tried to do a gig here in Spain using a Behringer X Air 12 and a Crown XTI 6000. At about 7 PM the mains voltage started to drop which sometimes happens in the campo (Country) the Xti was showing red low mains warning lights an kept going on and off. Does anyone know of a power amp with a universal power supply I.E 100 to 240 volts ?

[csg]

Powersoft X series will run on just about anything ( auto ranging and single / multi-phase). They also represent ( in my view of course) huge rise in sound quality over the XTI series of amps, but are also a little more expensive per channel and only come in 4 and 8 channel units.

[bigclive]

Something to keep in mind in areas where there is a poor power supply is that modern switchmode supplies with a wide voltage input range can cause an issue because they increase their current draw to compensate for the lowering voltage and where a lot of equipment is involved this can aggravate the problem.

[laolu]

I was thinking the same, so it's either 110V +/- some % OR 220V +/- some %, not continuous from 90 to 250V.

 

So when your amp said goodbye in Spain, the mains maybe just reached 190V or thereabouts, but wasn't low enough for the PSU to switch to the 110V range. I used to have a transformer (very heavy!!!) with a V-Meter and a wheel, with which I could do manual adjustments, but they are not made anymore, to my knowledge.

[Jivemaster]

Constant Voltage transformers exist but are heavy and likely specially wound to order. Wide range smpsu's exist but usually at low power. Variacs exist but again they are rare and expensive.

 

Maybe it's time to look at the feed to your location, or hire a generator.

[DrV]

Variacs ARE still made and widely available - RS, for example, has 60 different offerings. Can't argue with the fact that they are heavy though, and are fairly expensive - a 5A one in a case will set you back just over £200 and that doesn't include a voltmeter. Most will allow you to tap them so that they can step up as well as step down but you would need to monitor it closely in case the voltage came back up mid show and went out of spec in the other direction.

 

Regarding auto switching mentioned in your other thread:-

 

<br />The XTi work on either 120V or 230V but that's not on a sliding scale. The amp checks the mains voltage at first switch on and either selects 120V or 230V mode via a relay.<br />

 

The PSUs I have seen continuously monitor the input voltage and will switch between low voltage (doubler) configuration and high voltage (normal) configuration automatically if the supply is above or below a certain threshold. Can't speak specifically for the Xti though. However, if you are running just above the threshold the PSU may well be unable to regulate properly as it won't be doubling the mains but it may not have sufficient reservoir voltage for the PSU to operate correctly.

[Tim McCulloch]

Hello All, tried to do a gig here in Spain using a Behringer X Air 12 and a Crown XTI 6000. At about 7 PM the mains voltage started to drop which sometimes happens in the campo (Country) the Xti was showing red low mains warning lights an kept going on and off. Does anyone know of a power amp with a universal power supply I.E 100 to 240 volts ?

 

The acceptable voltage "window" for the XTi is fairly small, especially on the low end of the range. In the USA where nominal mains voltage can vary between 110v and 125v, the original XTi would shut down around 104v.

The PSU is not universal; it's a voltage sensing stepping supply so you need to supply either ~120V or ~240V OR whatever is labeled on the amp.

 

[alistermorton]

Little bit of history = the first Variac I got hold of was used for exactly this purpose - voltage stabilising. It was taken from an EMI test equipment rack, and it was controlled by a servo motor which in turn was controlled by a voltage sensing feedback amplifier.

[Jivemaster]

It's also possible to wire a mains to (say) 10 - 0 - 10 transformer as an auto-transformer and have switch selectable mains, mains +5% and mains +10%. A 100w transformer is often sufficient. All the caveats about competence and construction ability apply.

[alistermorton]

Essentially how my variac was used :-)

[Jivemaster]

It works to give a measured voltage increase, it's safe as long as the level is always low because it increases the upper voltage of the mains variation as well.

 

There are also UPS like devices that can level out mains voltage fluctuations by drawing extra current. Maybe one of the UPS manufacturers can help. Brownout protection from the internal battery is of very limited use as the battery never holds as much power/time as you want.

[alistermorton]

The centre tap on the variac meant you could or substract voltage.

[Jivemaster]

Obviously the servo operated variac is a very good tool, but usually now not easily found.

[adam2]

Mains voltage regulators are sold in countries were the mains voltage varies a lot.

 

Several types exist. One type uses an autotransformer with multiple tappings. The correct tapping is automatically connected via solid state switches.

 

Another type uses a variac AND a fixed ratio transformer. The fixed ratio transformer has a 208 volt primary and a 32 volt secondary. The 32 volt winding is connected in series with the output which is thereby boosted to the input mains voltage PLUS the voltage produced by the 32 volt winding.

 

The 220 volt winding is supplied from the mains via the variac.

 

Presume that the alleged 220 volt mains is actually 180 volts. The user would set the variac to "maximum" which would supply about 190 volts (about 105% of the 180 volt input) to the primary of the fixed ratio transformer. This will then produce about 30 volts which is added to the 180 volt incoming mains to give an output of about 210 volts which should be acceptable.

 

If the alleged 220 volt mains is in fact 200 volts, then the user would set the variac to about "two thirds" to give an output of about 140 volts. This 140 volts applied to the primary of the fixed transformer would produce about 20 volts which when added to the 200 volt mains input would produce 220 volts out.

 

 

 

 

This circuit can only boost a low line voltage, it can not reduce an excessive line voltage. An alternative circuit uses a fixed ratio transformer with a 100 volt or 110 volt primary that is connected between the centre tap of the variac and the moving contact. This can boost low line volts OR reduce high line volts.

 

Years ago I worked for a company that manufactured such equipment, they closed down decades ago, but similar equipment is still available.

 

 

 

[GaryNattrass]

Is the "Mains in Spain mainly lower on the Plains" http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif

 

I'll get me coat!