Anyone else have issues with their Lowel Omni lights?

Guy Cochran · February 27th, 2008, 01:19 PM

Just to chime in, I've use the same Omni in every major city in the US, across Canada and even in Mexico. Never a problem. We use the Oshram bulbs from Lowel and zero problems. Now the Pro Light with GCA's (250W) really need to be handled delicately, in fact, they don't ship with GCA's anymore, they now recommend the FVL (200W). A little less wattage, but much better lifespan.
We sell a couple Lowel DV Creator Kits per month and rarely hear of any issues besides the Pro Lights with GCA's.

Mike Barber · February 27th, 2008, 03:26 PM

Not being able to find a suitable dimmer/voltage controller locally (neither one meant for lights, nor something like the router controller... local because I can't wait for a shipment nor can afford to pay for next day service from US) I decided to employ my wits and feeble electrical skills (ok, my wits are pretty feeble too). Keep in mind what I am about to describ is my intended solution for Omni lights using FTK (that's 500w/120v, kids!) lamps.

My materials:
• Two sliding light dimmers rated for 600w (with a switched off position at the bottom)
• Two enclosures
• Two 5-foot 16-guage extension cords

Where I am going with this should be obvious: I cut an extension cord in two and connect the pieces to the sliding dimmer in order to make my own death trap... I mean, inline dimmer control.

I plugged it in and put my voltage meter on it. With the dimmer in the "off" position, I have no voltage registering. I switch it on, and I have the expected ~130v I get straight from the wall. What I am not getting is an expected change in voltage as I manipulate the dimmer. It keeps at a constant voltage.

Befuddled, I moved on to a real world test by testing my contraption on my cheap table lamp. In the "off" position the lamp is off. When I switch it on and manipulate the dimmer, I see expected results: the light dims with the setting of the dimmer. (Uh, I also blew the 40w/120v bulb when I pushed the dimmer up to 100%.)

So, it appears I do not have a voltage controller. I have no idea what I have, other than a waste of $$$ and resources. What could I have done wrong?

Mike Barber · February 27th, 2008, 06:21 PM

Quote:

Originally Posted by Michael Nistler

Many of us use Harbor Freight Router speed controllers to vary down voltage to our lights (good for up to 1500 watts)

Can you, or anyone else who has one, confirm that it actually reduces the voltage coming out? I ask because I was talking with someone at the local hardware store who told me there is no way to control the voltage, other than by calling in Quebec Hydro. I need to literally reduce voltage, and my contraption (see post #32) is not doing the job.

Jim Andrada · February 28th, 2008, 01:02 AM

I can't remember how much I've forgotten about this stuff since college, so I may be full of Sh--, but, saying voltage reduction can't be done except by the power company is BS.

I may be 1000% wrong, here but I think what you need to really reduce voltage is a variable transformer or Variac of some kind. I think the router speed controllers do their thing by dropping some of the AC cycles electronically, thus reducing the total power available in unit time. Which should also reduce your light output OK but not sure it will really do it by changing the voltage.

I think the household dimmers are more like variable resistors that just add some electrical load to the circuit. They can get quite hot in the process.

Damn, but I wish I could remember this stuff better. You'd never think I was once a Chemistry & Physics major - but then again it was almost 50 years ago.

Oh well, as they say, education is what's left after you forget every fact you learned in college.

Edit 1: OK - I found a readable link hat helps explain all this.

http://www.epanorama.net/documents/l...er.html#basics

It seems that in the 50 years since I was in college dimmers have gotten smarter and they also seem to work to reduce power rather than just add a resistive load or directly reduce voltage. As the gentleman says in the linked article, the components used today were not in existence when I was in school.

To net it out, these gadgets don't reduce voltage, they cut off power for some part of the cycle and in a sense increase percentage of the cycle where there is no current flowing.

Here's a quote from the link
_______________________Quote___________________\
Some light dimmer history

Light dimming is based on adjusting the voltage which gets to the lamp. Light dimming has been possible for many decades by using adjustable power resistors and adjustable transformers. Those methods have been used in movie theatres, stages and other public places. The problem of those light controlling methods have been that they are big, expensive, have poor efficiency and they are hard to control from remote location.

The power electronics have proceeded quickly since 1960. Between 1960-1970 thyristors and triacs came to market. Using those components it was quite easy to make small and inexpensive light dimmers which have good efficiency. Electronics controlling also made possible to make them easily controllable from remote location. This type of electronic light dimmers became available after 1970 and are nowadays used in very many locations like homes, restaurants, conference rooms and in stage lighting.

How modern light dimmers work ?

Solid-state light dimmers work by varying the "duty cycle" (on/off time) of the full AC voltage that is applied to the lights being controlled. For example, if the voltage is applied for only half of each AC cycle, the light bulb will appear to be much less bright than when it get the full AC voltage, because it get's less power to heat the filament. Solid-state dimmers use the brightness knob setting to determine at what point in each voltage cycle to switch the light on and off.

Typical light dimmers are built using thyristors and the exact time when the thyristor is triggered relative to the zero crossings of the AC power is used to determine the power level. When the the thyristor is triggered it keeps conducting until the current passing though it goes to zero (exactly at the next zero crossing if the load is purely resistive, like light bulb). By changing the phase at which you trigger the triac you change the duty cycle and therefore the brightness of the light.

Here is an example of normal AC power you get from the receptacle (the picture should look like sine wave):
... ...
. . . .
. . . .
------------------------------------ 0V
. . . .
. . . .
... ...
And here is what gets to the light bulb when the dimmer fires the triac on in the middle of AC phase:
... ...
| . | .
| . | .
------------------------------------ 0V
| . | .
| . | .
... ...
As you can see, by varying the turn-on point, the amount of power getting to the bulb is adjustable, and hence the light output can be controlled.

The advantage of thyristors over simple variable resistors is that they (ideally) dissipate very little power as they are either fully on or fully off. Typically thyristor causes voltage drop of 1-1.5 V when it passes the load current.

Edit 2: By the way, the little drawings look the same because the forum software seems to have dropped some blank spaces.

Mike Barber · February 28th, 2008, 01:16 AM

Quote:

Originally Posted by Jim Andrada

I can't remember how much I've forgotten about this stuff since college, so I may be full of Sh--, but, saying voltage reduction can't be done except by the power company is BS.

That's what i thought too... I mean, there's got to be a way... it's not rocket science, it's just voltage! And if I can build a DIY ring modulator or analogue synth (which uses small voltage controllers all over the place) then I should be able to rig something that can handle this load.

Quote:

Originally Posted by Jim Andrada

I think the household dimmers are more like variable resistors that just add some electrical load to the circuit.

And thus we reach the limits of my electrical understanding. I know just enough to know -- or at least think -- that i want to have a variable resistor (like a pot of some kind... yeah, like on my electric guitar, eh!) to add resistance in order to bring the voltage down. That's how I thought this stuff works... but this is all from learning on my own, and not necessarily well...

I am seriously doubting the ability to get this thing in the can within the next six days... unless I can get shooting done by Monday, I'm screwed. The budget is practically blown as it is. [insert string of profanity here]

Jim Andrada · February 28th, 2008, 01:31 AM

I think all is not lost! (By the way, I added an edit to the previous post that explains it a little better)

I think any place that sells motors etc can aim you at some place to get a voltage reducer/variac etc. And I think the woodworkers supply places can also aim you at such hardware or may even sell it themselves. I bought my single phase to 3 phase converter from an industrial woodworking supply shop.

I suspect they would sell router speed controls etc as well. These things aren't tremendously expensive as I recall.

Mike Barber · February 28th, 2008, 02:24 AM

Quote:

Originally Posted by Jim Andrada

I think the woodworkers supply places can also aim you at such hardware or may even sell it themselves.

I hope so... the people at Home Despot didn't have a clue as to what I was asking for until the third time i explained it. All they said was that they don't carry it... which surprised me, you'd think a place like that would! So far none of the hardware shops I've been to had it or knew where to get it.

Jim Andrada · February 28th, 2008, 03:24 AM

I wouldn't waste time in a hardware store - they're really unlikely to have anything useful. What you want is a commercial machinery place or a commerical or even advanced hobbyist woodworking or maybe even metal working store.

I Googled around and cmae up wih a couple of woodworking supply places in Montral

If I were you I'd call these guys or a similar place and ask about a router speed control or a variable transformer - I'm sure they'd know what you were talking about and be able to aim you in the right direction.

http://superpages.ca/bus/Quebec/Mont...?adid=01435600

http://www.rr-motors.com/

Or call harbour freight or woodcraft supply in the US and get them to FedEx you one overnight The one on harbour Freight was $10 and I doubt it would be very expensive to ship it.

Only one caution - these speed controls reduce power, not voltage per se. A variable transformer on the other hand will reduce the voltage.

One other thought - call an electrician and tell him you have an overvoltage problem and are blowing out equipment. Or call the electric company and explain your problem and ask them what they can recommend.

One more thought - the voltage regulators/battery backup units made for PC's may do the trick - I have a couple that are rated for 1500W and will boost low voltage/drop high voltage on the fly. Maybe a little pricier than some other option, but any reasonable sized computer store should have a couple of APC 1500W units around. In fact I've even seen them at Office Depot, Office Max etc. Some hot PC's pull 600W or so, so a couple of lights should be a piece of cake.

Craig Chartier · February 28th, 2008, 01:53 PM

here is what I can tell you about Omni's

We ran multiple Omni kits for years using only DYS 600 watt lamps.

I have rebuilt way too many of these fixtures

We always pull off the UL required safety wire screen. It holds in too much heat and causes both lamp failure as wel as refector failure.

we found out that Osram lamps have a smaller glass globe surrounding the element. on long strikes, the element wanders around inside and often come into contact with the glass, which causes lamp element to blow.

We only use USHIO for our DYS lamps because they have a very large glass globe surrounding the element. This has greatly increased lamp life.

hope this helps

Mike Barber · February 28th, 2008, 02:11 PM

Quote:

Originally Posted by Craig Chartier

We ran multiple Omni kits for years using only DYS 600 watt lamps.

Funny, I was just looking at those and wondering "hmmm, technically 100w over the stated limit, but rated for 125v... I wonder if I could get away with that?" when the notification of your post came in!

Just to make sure, is this what you've been using?

One thing I notice right away, and it may not matter at all but I need to ask, is that the base type for these are GZ9.5 (2-Pin Prefocus)... the base type for the FTK lamps I have are GY9.5 (2-Pin Prefocus)... close, but not exact... does it matter?

Craig Chartier · February 28th, 2008, 05:01 PM

yes that is what we use DYS, one pin larger than the other. see the larger globe size.

Michael Nistler · February 29th, 2008, 04:49 AM

Rehi all,

Forgive me for getting into the esoteric stuff - I wanted to clear up the misconception about gated dimmers. As we previously mentioned, our voltage in the United States in 117 volts alternating current at 60 hertz. Now then the 117vac is based in RMS (Root Mean Square) as opposed to the peak or average voltage - not that it really matters much to us for day to day stuff.

But when we use a gated (thyristor-based) dimmer, it reduces the peak of the sinusoidal 117vac wave form - no more RMS. This means the load, the Lowel Omni in our case has a lower applied voltage. Certainly the tungsten resistive load doesn't change and the current going through the bulb is predicated on the applied voltage. Incidentally, power is just another way to measure the current x voltage.

Bottom line, reducing the dimmer (of any type) means the bulb doesn't get as much heat applied to it, lasting a longer time. Again, I've found the Harbor Freight router speed controllers work great.

Okay? Michael

Vince Lucena · February 29th, 2008, 12:05 PM

That's great to hear, I ordered a few myself :)

Mike Barber · February 29th, 2008, 05:53 PM

Quote:

Originally Posted by Michael Nistler

Forgive me for getting into the esoteric stuff - I wanted to clear up the misconception about gated dimmers

I'm afraid I'm lost... the theory is going way over my head.

Quote:

Originally Posted by Michael Nistler

[...] when we use a gated (thyristor-based) dimmer, it reduces the peak of the sinusoidal 117vac wave form - no more RMS. This means the load [...] has a lower applied voltage.

But how do I measure that? All I understand is that, regardless of the dimmer position, ~127vac is coming out of the dimmer -- the same as if coming straight from the line. How can I gauge my dimmer position to know where I am reaching an 8% reduction? I need a sense of scale in order for this to be of any practical use.

Jim Andrada · February 29th, 2008, 05:58 PM

Michael,

I'm not sure what you mean by "no more RMS", since RMS (Root Mean Square) is just a calculation method that gives us a way to understand the total current from a fluctuating source. I don't think there's anything that requires a sinusoidal waveform in order to have an RMS value. Easy to calculate for a sine wave, though.

As I recall, peak voltage in the US is actually around +/-165 volts which would be equivalent to 117 volts RMS (which as you correctly say is the way AC line voltage is described)

As I understand it, thyristor based dimmers, router controls, etc essentially switch the current on and off quickly so for some period of time the voltage coming out the back end is zero. So the voltage coming out the back end, regardless of its peak value, is no longer sinusoidal. It looks like a sine wave with some gaps in it. The resultant back end (RMS) voltage is lower than the input RMS voltage. Not because the actual peak voltage has changed as much as because the shape of the curve has been changed (to have some periods of zero voltage,) therefore the total power/current in unit time is reduced.

Conceptually I think the gated dimmer/router control, etc is sort of like your kitchen blender - if you keep pulsing the switch on and off the motor never revs up to quite its full speed.

Anyhow, regardless, there are several ways to solve the original problem

1) Bulbs with higher voltage rating

2) Lower average voltage (hence lower temperature) achieved by gating the circuit

3) Lower average voltage caused by lowering the actual peak voltage with a transformer.

4) Other

For resistive loads like a lamp bulb, either 2) or 3) should be fine. For other applications, maybe they're not equivalent.

February 27th, 2008, 01:19 PM	#31
Guy Cochran DVCreators.Net Join Date: Oct 2001 Location: Seattle, WA Posts: 892	Just to chime in, I've use the same Omni in every major city in the US, across Canada and even in Mexico. Never a problem. We use the Oshram bulbs from Lowel and zero problems. Now the Pro Light with GCA's (250W) really need to be handled delicately, in fact, they don't ship with GCA's anymore, they now recommend the FVL (200W). A little less wattage, but much better lifespan. We sell a couple Lowel DV Creator Kits per month and rarely hear of any issues besides the Pro Lights with GCA's. __________________ Guy Cochran DVinfo Sponsor, Cool Gear - DVeStore!

February 29th, 2008, 04:49 AM	#42
Michael Nistler Major Player Join Date: Aug 2006 Location: Petaluma, CA Posts: 456	Electrical Geek-speak Rehi all, Forgive me for getting into the esoteric stuff - I wanted to clear up the misconception about gated dimmers. As we previously mentioned, our voltage in the United States in 117 volts alternating current at 60 hertz. Now then the 117vac is based in RMS (Root Mean Square) as opposed to the peak or average voltage - not that it really matters much to us for day to day stuff. But when we use a gated (thyristor-based) dimmer, it reduces the peak of the sinusoidal 117vac wave form - no more RMS. This means the load, the Lowel Omni in our case has a lower applied voltage. Certainly the tungsten resistive load doesn't change and the current going through the bulb is predicated on the applied voltage. Incidentally, power is just another way to measure the current x voltage. Bottom line, reducing the dimmer (of any type) means the bulb doesn't get as much heat applied to it, lasting a longer time. Again, I've found the Harbor Freight router speed controllers work great. Okay? Michael

February 29th, 2008, 12:05 PM	#43
Vince Lucena Regular Crew Join Date: May 2006 Location: Virginia Beach, Va Posts: 91	That's great to hear, I ordered a few myself :) __________________ ......................... MotionOne Studios http://www.MotionOne.tv

February 27th, 2008, 03:26 PM	#32
Mike Barber Major Player Join Date: May 2006 Location: Toronto ON Canada Posts: 731	Trying to fix it, MacGyver style... Not being able to find a suitable dimmer/voltage controller locally (neither one meant for lights, nor something like the router controller... local because I can't wait for a shipment nor can afford to pay for next day service from US) I decided to employ my wits and feeble electrical skills (ok, my wits are pretty feeble too). Keep in mind what I am about to describ is my intended solution for Omni lights using FTK (that's 500w/120v, kids!) lamps. My materials: • Two sliding light dimmers rated for 600w (with a switched off position at the bottom) • Two enclosures • Two 5-foot 16-guage extension cords Where I am going with this should be obvious: I cut an extension cord in two and connect the pieces to the sliding dimmer in order to make my own death trap... I mean, inline dimmer control. I plugged it in and put my voltage meter on it. With the dimmer in the "off" position, I have no voltage registering. I switch it on, and I have the expected ~130v I get straight from the wall. What I am not getting is an expected change in voltage as I manipulate the dimmer. It keeps at a constant voltage. Befuddled, I moved on to a real world test by testing my contraption on my cheap table lamp. In the "off" position the lamp is off. When I switch it on and manipulate the dimmer, I see expected results: the light dims with the setting of the dimmer. (Uh, I also blew the 40w/120v bulb when I pushed the dimmer up to 100%.) So, it appears I do not have a voltage controller. I have no idea what I have, other than a waste of $$$ and resources. What could I have done wrong? __________________ Mike Barber "I'm laughing to stop myself from screaming."

February 28th, 2008, 01:02 AM	#34
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	I can't remember how much I've forgotten about this stuff since college, so I may be full of Sh--, but, saying voltage reduction can't be done except by the power company is BS. I may be 1000% wrong, here but I think what you need to really reduce voltage is a variable transformer or Variac of some kind. I think the router speed controllers do their thing by dropping some of the AC cycles electronically, thus reducing the total power available in unit time. Which should also reduce your light output OK but not sure it will really do it by changing the voltage. I think the household dimmers are more like variable resistors that just add some electrical load to the circuit. They can get quite hot in the process. Damn, but I wish I could remember this stuff better. You'd never think I was once a Chemistry & Physics major - but then again it was almost 50 years ago. Oh well, as they say, education is what's left after you forget every fact you learned in college. Edit 1: OK - I found a readable link hat helps explain all this. http://www.epanorama.net/documents/l...er.html#basics It seems that in the 50 years since I was in college dimmers have gotten smarter and they also seem to work to reduce power rather than just add a resistive load or directly reduce voltage. As the gentleman says in the linked article, the components used today were not in existence when I was in school. To net it out, these gadgets don't reduce voltage, they cut off power for some part of the cycle and in a sense increase percentage of the cycle where there is no current flowing. Here's a quote from the link _______________________Quote___________________\ Some light dimmer history Light dimming is based on adjusting the voltage which gets to the lamp. Light dimming has been possible for many decades by using adjustable power resistors and adjustable transformers. Those methods have been used in movie theatres, stages and other public places. The problem of those light controlling methods have been that they are big, expensive, have poor efficiency and they are hard to control from remote location. The power electronics have proceeded quickly since 1960. Between 1960-1970 thyristors and triacs came to market. Using those components it was quite easy to make small and inexpensive light dimmers which have good efficiency. Electronics controlling also made possible to make them easily controllable from remote location. This type of electronic light dimmers became available after 1970 and are nowadays used in very many locations like homes, restaurants, conference rooms and in stage lighting. How modern light dimmers work ? Solid-state light dimmers work by varying the "duty cycle" (on/off time) of the full AC voltage that is applied to the lights being controlled. For example, if the voltage is applied for only half of each AC cycle, the light bulb will appear to be much less bright than when it get the full AC voltage, because it get's less power to heat the filament. Solid-state dimmers use the brightness knob setting to determine at what point in each voltage cycle to switch the light on and off. Typical light dimmers are built using thyristors and the exact time when the thyristor is triggered relative to the zero crossings of the AC power is used to determine the power level. When the the thyristor is triggered it keeps conducting until the current passing though it goes to zero (exactly at the next zero crossing if the load is purely resistive, like light bulb). By changing the phase at which you trigger the triac you change the duty cycle and therefore the brightness of the light. Here is an example of normal AC power you get from the receptacle (the picture should look like sine wave): ... ... . . . . . . . . ------------------------------------ 0V . . . . . . . . ... ... And here is what gets to the light bulb when the dimmer fires the triac on in the middle of AC phase: ... ... \| . \| . \| . \| . ------------------------------------ 0V \| . \| . \| . \| . ... ... As you can see, by varying the turn-on point, the amount of power getting to the bulb is adjustable, and hence the light output can be controlled. The advantage of thyristors over simple variable resistors is that they (ideally) dissipate very little power as they are either fully on or fully off. Typically thyristor causes voltage drop of 1-1.5 V when it passes the load current. Edit 2: By the way, the little drawings look the same because the forum software seems to have dropped some blank spaces.

February 28th, 2008, 01:31 AM	#36
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	I think all is not lost! (By the way, I added an edit to the previous post that explains it a little better) I think any place that sells motors etc can aim you at some place to get a voltage reducer/variac etc. And I think the woodworkers supply places can also aim you at such hardware or may even sell it themselves. I bought my single phase to 3 phase converter from an industrial woodworking supply shop. I suspect they would sell router speed controls etc as well. These things aren't tremendously expensive as I recall.

February 28th, 2008, 03:24 AM	#38
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	I wouldn't waste time in a hardware store - they're really unlikely to have anything useful. What you want is a commercial machinery place or a commerical or even advanced hobbyist woodworking or maybe even metal working store. I Googled around and cmae up wih a couple of woodworking supply places in Montral If I were you I'd call these guys or a similar place and ask about a router speed control or a variable transformer - I'm sure they'd know what you were talking about and be able to aim you in the right direction. http://superpages.ca/bus/Quebec/Mont...?adid=01435600 http://www.rr-motors.com/ Or call harbour freight or woodcraft supply in the US and get them to FedEx you one overnight The one on harbour Freight was $10 and I doubt it would be very expensive to ship it. Only one caution - these speed controls reduce power, not voltage per se. A variable transformer on the other hand will reduce the voltage. One other thought - call an electrician and tell him you have an overvoltage problem and are blowing out equipment. Or call the electric company and explain your problem and ask them what they can recommend. One more thought - the voltage regulators/battery backup units made for PC's may do the trick - I have a couple that are rated for 1500W and will boost low voltage/drop high voltage on the fly. Maybe a little pricier than some other option, but any reasonable sized computer store should have a couple of APC 1500W units around. In fact I've even seen them at Office Depot, Office Max etc. Some hot PC's pull 600W or so, so a couple of lights should be a piece of cake.

February 28th, 2008, 01:53 PM	#39
Craig Chartier DVi Contributor Join Date: Mar 2006 Location: Austin Texas Posts: 374	here is what I can tell you about Omni's We ran multiple Omni kits for years using only DYS 600 watt lamps. I have rebuilt way too many of these fixtures We always pull off the UL required safety wire screen. It holds in too much heat and causes both lamp failure as wel as refector failure. we found out that Osram lamps have a smaller glass globe surrounding the element. on long strikes, the element wanders around inside and often come into contact with the glass, which causes lamp element to blow. We only use USHIO for our DYS lamps because they have a very large glass globe surrounding the element. This has greatly increased lamp life. hope this helps

February 28th, 2008, 05:01 PM	#41
Craig Chartier DVi Contributor Join Date: Mar 2006 Location: Austin Texas Posts: 374	yes that is what we use DYS, one pin larger than the other. see the larger globe size.

February 29th, 2008, 05:58 PM	#45
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	Michael, I'm not sure what you mean by "no more RMS", since RMS (Root Mean Square) is just a calculation method that gives us a way to understand the total current from a fluctuating source. I don't think there's anything that requires a sinusoidal waveform in order to have an RMS value. Easy to calculate for a sine wave, though. As I recall, peak voltage in the US is actually around +/-165 volts which would be equivalent to 117 volts RMS (which as you correctly say is the way AC line voltage is described) As I understand it, thyristor based dimmers, router controls, etc essentially switch the current on and off quickly so for some period of time the voltage coming out the back end is zero. So the voltage coming out the back end, regardless of its peak value, is no longer sinusoidal. It looks like a sine wave with some gaps in it. The resultant back end (RMS) voltage is lower than the input RMS voltage. Not because the actual peak voltage has changed as much as because the shape of the curve has been changed (to have some periods of zero voltage,) therefore the total power/current in unit time is reduced. Conceptually I think the gated dimmer/router control, etc is sort of like your kitchen blender - if you keep pulsing the switch on and off the motor never revs up to quite its full speed. Anyhow, regardless, there are several ways to solve the original problem 1) Bulbs with higher voltage rating 2) Lower average voltage (hence lower temperature) achieved by gating the circuit 3) Lower average voltage caused by lowering the actual peak voltage with a transformer. 4) Other For resistive loads like a lamp bulb, either 2) or 3) should be fine. For other applications, maybe they're not equivalent.