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Author Topic: 120 vac and 220 vac  (Read 1918 times)
KC6WGN
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« on: April 09, 2010, 05:02:09 PM »

What is the difference when I wired my amplifier to 120 vac or 220 vac? What is the results of the output of the amplifier?
thanks...
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NI3S
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« Reply #1 on: April 09, 2010, 05:10:08 PM »

Amplifier output is probably the same.  The current going in will be halved on 220VAC, so the wire can be smaller, and cheaper.
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K5DVW
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« Reply #2 on: April 09, 2010, 05:58:06 PM »

In simple terms, the only reason to go with 240V is if the 120V sags too much during transmit. Sagging 120V can reduce the output power of the amplifier. If it's not sagging, then you wont gain anything.

The amp will pull half the current off 220V which will reduce the voltage drop in the wall voltage. You know, V=I*R?
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NA0AA
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« Reply #3 on: April 09, 2010, 06:33:01 PM »

Ah, well, many amplifiers will draw more current than a 120 volt circuit can provide [usually 15 amps in a residence], so a 240 volt circuit is needed to provide enough power.  I'm not aware of any legal limit amps that do not require 240 volts.

Some amplifiers will only develop partial power on 120 volts - I believe either the Icom or Yaesu solid state amps do that.  Or you will be limited by the voltage drop.

For best, most stable operation, you almost have to run an amplifier on a dedicated circuit.
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W7KKK
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« Reply #4 on: April 09, 2010, 06:52:58 PM »

The problem for most is that at best you have a 20 amp circuit you are using at 120 volts. Most don't have that so an amp that draws near that on a circuit with anything else is really pushing it.
What type of amp are you running, it may help us better understand?
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K0OD
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« Reply #5 on: April 09, 2010, 07:11:40 PM »

Years ago I had an electrician install a 220V line for my Heath SB-220 amp. I ran a bunch of tests the day before he arrived.

When the amp was moved to the 220V circuit (from 110), maximum output went up several hundred watts and room lights stopped dimming when I hit the key.

Go with 220 if you have a big amp.
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W8JI
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« Reply #6 on: April 10, 2010, 02:50:16 AM »

What is the difference when I wired my amplifier to 120 vac or 220 vac? What is the results of the output of the amplifier?
thanks...

There is no 220V in residential USA, it is all from a center tapped transformer so it is 120 or 240. The last of the 110/220 lines went away in the 1960's and 70's.

Typically the 240 volt line is 245 volts because most utilities run a tad high off peak loads.

Always go by percentage when thinking above changes in regulation.

You would decrease power line sag, as a PERCENTAGE, by four times for the same load and wire gauge. If you had around 10% drop at 120 (from 120 to 108 volts) you would have 2.5% drop at 240 volts on the same wire. This would be from 240 to 234 volts.

How this affects an amplifier depends a great deal on the amplifier. In some amplifiers, most of the voltage drop under load is in the power supply. This means you would NOT see the full ~7 % improvement  in regulation on meters in the amp because the internal supply might have more drop than the mains, and it should be unaffected by the change.

The single most important reason to change to 240 is because the amplifier is getting near limits of the power mains. I run most of my 1000 watt and lower output amplifiers off 120 volts here. All of my stuff over that level runs from 240 because of the required current, not because of voltage drop. The primary improvement is how much power I can pull before the mains breaker trips. My wiring is good enough I don't get much light dimming even if I pull 20 amps off my mains.

73 Tom
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W8JI
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« Reply #7 on: April 10, 2010, 02:56:48 AM »

Years ago I had an electrician install a 220V line for my Heath SB-220 amp. I ran a bunch of tests the day before he arrived.

When the amp was moved to the 220V circuit (from 110), maximum output went up several hundred watts and room lights stopped dimming when I hit the key.

Go with 220 if you have a big amp.

The rated carrier power output of the SB220 is about 600 watts. The rated PEP OUTPUT power is about 1200 watts.

Several hundred watts is a huge output power change considering the amp only runs 600 watts CW carrier at rated power input.
:-)



I can change my SB220 from 120 to 240 here (and back), and the change in output power is barely noticable. Maybe 50-100 watts maximum. I had 14-2/G wiring about 35 feet long to the mains when I changed my amp to 240. That's hammering the amp way past ratings, at about 900-1000 watts out by running it on CW using the SSB voltage position.


73 Tom
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KC6WGN
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« Reply #8 on: April 10, 2010, 08:25:10 AM »

Henry amplifier 2KD Classic...thanks...
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KB1LKR
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« Reply #9 on: April 10, 2010, 09:23:52 AM »

Actually in North America it is 120 or 240V (2*120V), excepting commercial 3 phase services were is it usually 120V & 208V (sqrt(3)*120V). 220V (or 230V) are common in Europe outside the 240V UK.

The difference to the Amp is the circuit wiring from the power panel to the amp receptacle (or even thru the amp cord to its input transformer) carries half the current at 240V therefore incurs half the voltage drop on the wiring assuming the same size wire is used (say 2*12 AWG + gnd) for a 20 amp circuit), so the line voltage to the Amp is more stable as the output rises and falls. A 15 Amp (14 AWG) circuit will have roughly 33% greater voltage drop than a 20A circuit at the same line voltage.

Note that only two wires (plus a safety ground) are all that is required for either voltage, though 240V requires a 2 pole breaker vs. a 1 pole breaker. only dual voltage circuits (e.g. ranges and cloths dryers) require a third (neutral) power wire.
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N2EY
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« Reply #10 on: April 10, 2010, 02:06:01 PM »


Note that only two wires (plus a safety ground) are all that is required for either voltage, though 240V requires a 2 pole breaker vs. a 1 pole breaker. only dual voltage circuits (e.g. ranges and cloths dryers) require a third (neutral) power wire.

This brings up a DON'T DO THIS caution, if you're not used to working with 240 volt supply...

Every amp I've seen that will run on either voltage has a dual-primary-winding power transformer. The windings are in series for 240 and parallel for 120. Properly phased, of course.

What you must never do when running 240 volt supply is to connect the the midpoint of the two primary windings (the jumper that puts them in series) to the safety ground or neutral. It should simply float.

The reason for letting it float has to do with the way the supply works. The 120/240 circuits come from a center-tapped transformer at the pole or pad. If you connect another transformer across all three wires, it will act as a center-tapped autotransformer and try to balance the voltage on both sides.

If both 120 volt legs are the exact same voltage, there's no problem. But that almost never happens, so the amp's transformer will try to force it to happen. This puts an added load on it that may or may not trip a breaker, but which isn't good for the transformer at all.

No, I didn't learn that the hard way.

73 de Jim, N2EY

« Last Edit: April 10, 2010, 07:33:39 PM by James Miccolis » Logged
VK1OD
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« Reply #11 on: April 10, 2010, 02:51:32 PM »

...
What you must never do when running 240 volt supply is to connect the the midpoint of the two primary windings (the jumper that puts them in series) to the safety ground or neutral. It should simply float.

Jim, I know that much of eHam is answers without explantion, and that you usually offer explanations.

Perhaps you should flatter your audience with an explanation in this case.

Owen
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K0OD
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« Reply #12 on: April 10, 2010, 03:42:53 PM »

"When the amp was moved to the 220V circuit (from 110), maximum output went up several hundred watts and room lights stopped dimming when I hit the key."

Wouldn't moving the amp to 240 reduce some voltage drop on the exciter too, thus increasing its output?

Amp was on a bedroom outlet on a long run of aluminum wire from the panel. My before/after measurement was done about 25 years ago. I don't remember the exact improvement but I was thrilled with the benefits.
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AA4PB
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« Reply #13 on: April 10, 2010, 04:02:48 PM »

That's the problem with existing 120V circuits, they almost always have other things running from them. If you had a dedicated 120V, 20A circuit with a reasonable length run from the electric panel then it would be fine if it was only powering the amp. Add lights, the transceiver, accessories, and who knows what else and you're likely to have a problem.

If you are going to put in a dedicated circuit then you might as well make it 240V, 20A and reduce the voltage drop in the circuit. Most amps on 240V don't have a neutral connection so you can use the exact same 12-2/w gnd cable that you use for 120V circuits. Mark the ends of the white wire with a piece of black electrical tape to signal that it is being used for a "hot" connection.


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K5DVW
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« Reply #14 on: April 10, 2010, 05:38:39 PM »

>What you must never do when running 240 volt supply is to connect the the midpoint of the two primary windings (the jumper that puts them in series) to the safety ground or neutral. It should simply float.

How's it wired at the distribution transformer?
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