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#127493 - 07/29/01 11:52 AM Discussions on: HID CWA Ballasts
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Discussion thread regarding Schematics for the Constant Wattage Autotransformer [CWA] type Ballasts, for use with Mercury Vapor [MV], Metal Halide [MH], or High Pressure Sodium [HPS] lamps.

These Schematics are found in the Technical Reference area, under the topic heading:

HID Ballast Schematics: CWA

Fig. 3.1. = Constant Wattage Autotransformer Ballast with "Quadri-Volt" input - for driving one Mercury Vapor, or Metal Halide lamp.

Fig. 3.2. = CWA Ballast with "Quadri-Volt" input - for driving one High Pressure Sodium, or "Pulse Start" Metal Halide lamp.

Fig. 3.3. = CWA Ballast with "Quadri-Volt" input - for Independent [parallel] operation of two H33 or M59 lamps.

These Ballasts have a common conductor which is common to both the input and the lamp screwshell. This common conductor should be connected to the system's grounded conductor, so the hazard of a live screwshell is minimized. That helps to reduce the "Shocking Experience" found when the screwshell of a lamp has L-G [Line to Ground] potential.
That Scenario is often followed by the tossing of said lamp, loud and extreme obscene word strings/phrases, and an almost certain crash course in Newtons laws of motion and 1st hand experience of the transfer of potential energy to kinetic energy - when contact is made to the ground below [AKA potential energy = Sparky's mass- in Kgs, by the length of fall (ladder height = min. 8 Meters) = kinetic energy at concrete slab]. This formula does not take in to consideration the kinetic energy released in swear words or blood loss, after impact.

Any Comments??? [there's gotta be some ]

Scott SET
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#127494 - 11/07/03 08:44 AM Re: Discussions on: HID CWA Ballasts
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
with reference to the high pressure sodium constant wattage auto transformers, how does the ignitor work? Does it stop and start the supply to make the reactor section produce high voltages to strike the sodium?if so why does inductive reactance not oppose the rapid change in voltage?
Also which coil limits the current once the lamp is illuminated?
And finally what kind of voltage are we looking at on the link between the auto and reactor coils?

also to agree with the guys in this section (on another topic)your doing a great job i to have learned a lot more since using the forum and enjoy being able to ask others with more experience and knowledge cheers mate



[This message has been edited by james S (edited 11-07-2003).]

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#127495 - 11/10/03 03:52 AM Re: Discussions on: HID CWA Ballasts
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
James S;

Thanks for the reply regarding the Schematic(s)!

Below is some information per your questions:

1:
with reference to the high pressure sodium constant wattage autotransformers, how does the ignitor work?

The Ignitor is a string of "Tank Circuits" - composed of Capacitor / Resistor / Diode elements, which create a pulse of current being pushed by a high voltage.
The Tank Circuit used with the Ignitor is similar to the Tank Circuit used for firing the flash lamp on Portable Cameras (builds a voltage of >90V from the ±3V power from the "AA" Drycells).

2:
Does it stop and start the supply to make the reactor section produce high voltages to strike the sodium?

Actually it works as a "Stand-Alone" component, which is current limited by the Reactor, and has its own tapped lead from the Reactor.
During all operations - starting thru normal operation, the Reactor works as normal.
Ignitor will operate during "High Impedance" situations with the lamp (AKA no arc time, along with missing lamp).
Once the lamp has established an arc, the Impedance becomes low, which results in the bulk amount of current flowing thru the lamp, instead of thru the Ignitor.

3:
if so why does inductive reactance not oppose the rapid change in voltage?

Inductive Reactance occurs with a changing current, and side effects are a counter EMF pushing an inductive current backflow (in very basic terms!).
The Reactor's main function is to "React" against a level of current flowing thru the complete circuit (lamp + ballast), so the lamp does not destroy its self from excessive current draw.

4:
Also which coil limits the current once the lamp is illuminated?

The Reactor section / coil does the current limiting throughout the operation - from startup to normal operation.

5:
And finally what kind of voltage are we looking at on the link between the auto and reactor coils?

For Medium based HPS lamps, the voltage will be a nominal 55 volts at the Reactor's output to the lamp. Nominal being the target operating voltage. It will raise and lower depending on the lamp's state of operation.
The voltage between the autotransformer and the reactor input for the same lamps will be 100-120 volts.
For Mogul based HPS lamps, the reactor output nominal voltage will be around 100 volts, with apx. 180-210 volts between the autotransformer's output and the reactor's input.
Pulse ignitor's output is around 1500 volts nominal - depending on the lamp's age and condition, along with the arc tube's temperature.

6:
also to agree with the guys in this section (on another topic) your doing a great job

Thank you for the kind words! Glad to be of help!

7:
I too have learned a lot more since using the forum and enjoy being able to ask others with more experience and knowledge

That's what we're all here for!!! Once again, glad to be apart of this!

8:
cheers mate

See 'ya later, Gator

Scott35

p.s. edited some baad spel-ling, but probably not all of it!

[This message has been edited by Scott35 (edited 11-10-2003).]
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#127496 - 10/25/04 02:17 PM Re: Discussions on: HID CWA Ballasts
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
sorry to bother you again on the same subject scott :-(

The way the current ballasts im working on are wired up is the same as fig 3.2 but the ballast has no neutral connected to it and (as far as i know) no capacitor linking the two coils unless internal.ps what is that cap for?


-live into ballast
-line out of ballast to ignitor then on to lamp (x1)
-second line out of ballast to ignitor (x3)
-neutral to ignitor (x2)
-neutral to lamp
-earth to case of ballast

do you think the ballast gets its neutral via the ballast?

only caps used are for p,f correction
just dont get it!
unless the ballast is just like an in line resistor limiting the current?

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#127497 - 10/26/04 08:00 PM Re: Discussions on: HID CWA Ballasts
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Hello again, James!
Definitely not bothering me at all!

Per the last post, I'll quote the appropriate text above my replies.

 Quote:

The way the current ballasts I'm working on are wired up is the same as fig 3.2, but the ballast has no neutral connected to it, and as far as I know, no capacitor linking the two coils (unless internal).


Likely, this would be a "Standard" Linear Reactor type setup.
From the Connection description at the end of the latest post, it really points towards a Linear Reactor setup.

Here is a Schematic for the Linear Reactor Ballast, which is used with either a Metal Halide Pulse Start Lamp, or an HPS Lamp:



Here is the CWA Ballast Schematic for Pulse Start Metal Halide and HPS Lamps:



More information may be found regarding the Linear Reactor Ballasts at the Technical Reference area. Just click the link text to go there (the underlined "Linear Reactor Ballasts" text).

In all connection examples the "Common" Conductor, used with HID Ballasts, does not necessarilly need to be the System's Grounded Conductor in order for the Assembly to operate correctly.
In many scenarios - such as connections using input Voltages like 208 VAC and 240 VAC, these would definitely not use a Grounded System Conductor on the "Common" side of the Ballast, but instead would use an "Opposing Phase" Ungrounded Conductor on the "Common" side of the Ballast.

As far as the Capacitor in this case - and the setup being a simple Linear Reactor Ballast, the input would have an "Optional Capacitor" connected, to improve the Power Factor seen by the Power Supply.
A bit more detail in the next reply below.

 Quote:

ps: what is that cap for?


Typically a Capacitor will be used to improve Power Factor, as seen by the Power Supply, but in some cases of HID Ballasts, it plays a secondary role; Lamp Regulation (along with PF correction).

Lamp Regulation is a bit lengthy of discussion (so is Power Factor!), so for this case we will just cover the simple parts of the P.F. thing.

The Ballast and Lamp combination, under normal operation, results in a Lagging Power Factor (an Inductive Reactance load). The Power Factor is around 50% (0.5) - which would result in an input Current flow of twice the level required to deliver the True Power rating of the Lamp.

Example:
100 Watt Lamp,
System Voltage = 100 VAC
Power Factor = 0.50
Input Amperes = 2.0 Amps @ 100 VAC,
Input Apparent Power (Volts × Amps) = 200 VA (Volt-Amps).
The VA figure carries the True Power (Wattage), along with the Reactive Power (VARs, or Volt-Amps Reactive).

In order to keep from having to "Recharge" the Ballast with the Reactive Power (the "VARs"), we can "Store" them near the Ballast Load, using a Capacitor.
Now, the Ballast only needs to be "Charged" minimally with the VARs, and they are "Kept" near the Ballast Load via the Capacitor.
The input VA is reduced, and so is the input Line Amperes, and consequentially, the overall Power Factor has been improve by including the Capacitor.

 Quote:

-live into ballast
-line out of ballast to ignitor then on to lamp (x1)
-second line out of ballast to ignitor (x3)
-neutral to ignitor (x2)
-neutral to lamp
-earth to case of ballast


This appears to be a Linear Reactor setup.
Check out the Schematic, and compare it to your Ballasts, then let me know if they are Linear Reactors.

 Quote:

do you think the ballast gets its neutral via the ballast?


As mentioned previously, the Ballast does not require a "Neutral Type Conductor" (Grounded Conductor), only that the input be a "Usable 2-Wire Circuit".
By this I mean a Circuit - this being of at least two individual Conductors, with a Potential Difference between them - and being ones that are intended for use as "Normal Circuit Conductors".

"Normal Circuit Conductors" being Ungrounded And/or Grounded Conductors, not Equipment Grounding Conductors (or Grounded/Bonded Equipment) being used for Normal Circuitry.

"Potential Difference Between Conductors" meaning "A Substantial Voltage Reading Between Conductors", which results in a Current Flow.
All above to be designed and installed intentionally and safely, per common techniques.

So, to make some sense here , either two Ungrounded Conductors - of opposite polarity, or one Ungrounded conductor and one Grounded Conductor, may be used to drive the Ballast.
In the case a Grounded Conductor is used, it Should be connected to the "Common" section of the Ballast.

 Quote:

only caps used are for p,f correction
just dont get it!
unless the ballast is just like an in line resistor limiting the current?


Most ballasts will use Capacitors for both P.F. Correction and Lamp Regulation.
Linear Reactor types use the Capacitor solely for P.F. Correction.

You are correct about the Ballast being like an In-Line Resistor to limit the Current!
That is the primary function of all Ballasts - for HID Lamps, Fluorescent Lamps and Neon Lamps.
These Discharge Lamps have a Negative Resistance effect, which allows them to draw high levels of Current, in a "Domino Effect" fashion.
The higher the Current flow is, the more conductive the Lamps Arc becomes - and therefore allows more Current to flow - which makes the Arc more conductive... etc., to the point where the Lamp "Kills Itself"

Let me know if this reply describes what you need, or if there are additional questions.

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#127498 - 10/27/04 12:56 PM Re: Discussions on: HID CWA Ballasts
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
Thanks for the detailed reply scott!!!!!!

your reply is a big help and discribes just what i needed and is very much appreciated, but like usual it opens more questions

i know the ignitor consists of capacitors,an diodes but how does it know to stop when low impedances are present.

is the reactor producing the high voltage or is it the caps inside the ignitor?
if it is the caps why not feed the ignitor straight off the mains supply?

thanks again for your time

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#127499 - 10/27/04 02:51 PM Re: Discussions on: HID CWA Ballasts
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Hi again James! Glad the last message was helpful.

With the Pulse Ignitor, it produces high powered pulses when it is the "Easiest Path For Current To Flow Through" - such as when the Lamp has no arc established across the tube.

Prior to Lamp ignition (no arc established), the Lamp is a very high Impedance - but still Conductive.
Consequentally (sp???), the Ignitor is a much lower Impedance at this time, so higher Current levels flow through the Pulse Ignitor, and towards the differences in Potential. In this case, high flow heads to the "Common" side of the input Circuitry.

Not all the Current flows straight through it to the Common side; some Current is retained within the Tank Circuitry - resulting in the output Pulses of Current under a high voltage.
These pulses see a lower opposition path through the Lamp than through the Tank Circuitry of the Ignitor, so the Pulsed Current flows through the Lamp's Arc Tube, then to the "Common" side of the input Circuitry.

Pulses continue in this fashion until the Lamp's Impedance changes (arc is established).

Once the Lamp's Arctube has an established Arc within it, the Lamp now has much lower Impedance than the Pulse Ignitor, so the higher levels of Current flow through the Lamp, and very small levels of Current flow through the Pulse Ignitor.
Since the Lamp has such a low Impedance now, the Tank Circuitry of the Pulse Ignitor will not be able to create a high voltage, whereas previously it built up a high voltage against the high Lamp Impedance.
So now, there is no high voltage output pulsed current, and since the Lamp has drammatically lower Impedance at this time (compared to the Ignitor's Pulse Circuitry), very little Current flows through the Tank Circuit as well.

It all has to do with which one is the lowest Impedance at the time. The lowest Impedance device will allow the highest Current to flow.
When the Ignitor is the lower Impedance, it uses the high Impedance of the Lamp to build up a high voltage, by attempting to push a burst of Current through that Impedance.
Once the Plasma is setup, the Lamp's Impedance nearly dissappears right away, and eventually the Lamp becomes negative Resistance.

Lastly, the Ignitor is fed through the Reactor section, so the Current can be limited.
If connected across the input line, the Lamp would be able to draw input Current through the Pulse Ignitor without any regulating / limiting / choking factor; therefore will destroy its self, almost immediately.
The Ignitor will just pass Current to the Lamp.

Sounds odd, doesn't it? By limiting the level of Current, the Ignitor works as intended, plus the Lamp operates as indended.

Glad to be of help here, even if each of my replies results in more questions!
BTW, that's what is supposed to happen!!!

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#127500 - 11/19/04 12:04 PM Re: Discussions on: HID CWA Ballasts
james S Offline
Member

Registered: 05/13/03
Posts: 102
Loc: West England
thanks for your reply scott very helpful!!

just a couple of points;
is the ballast polarised as the fitting fails to work if you swap the input for the output and out for the in?i dont think the ignitor plays any part in this as it works at any tapping on the ballast (there is different voltage tappings)
and also the fitting fails to operate if the tapped lead for the ignitor is taken off the out going of the ballast,i cant see any reason why this will not work.

thanks again for all your efforts on this subject even though it may have become boring for you!!!!!



[This message has been edited by james S (edited 11-26-2004).]

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#127501 - 08/06/05 06:02 PM Re: Discussions on: HID CWA Ballasts
Spewn Offline
Junior Member

Registered: 08/06/05
Posts: 1
Digging up another old thread, I'm afraid, but it has to be done!

This question is more specifically about CWI ballasts, but it fits best here I think. Since the only difference between the circuitry for an HPS ballast and a MH ballast is the ignitor, if you had an HPS ballast that you wanted to switch over to running an MH lamp could you simply remove the ignitor from the circuit? I'm thinkin in terms of retrofitting places that have the not-so-pretty(but slightly more efficient) HPS lighting but would look a lot better with MH lighting.

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