Measuring Voltage from Ballast?

J. Montgomery · 08/12/2007, 07:48 PM

Someone asked me what voltage my ballast was running my bulbs (Blue Wave II: 175W dual magnetic pulse start: M137). I have a voltage meter, is there a safe way that I can measure the voltage from the ballast without severely injuring myself?

AZDesertRat · 08/12/2007, 08:58 PM

Only to the ballast not from the ballast. The ballast is a transformer and amplifies the power tremendously to power the bulbs.

israelnajar · 08/12/2007, 09:18 PM

This plus ohms law

AZDesertRat · 08/12/2007, 09:37 PM

That and Ohms law are fine on the incoming side. A ballast can put out hundreds or even thousands of volts depending on the application. Input and output are two entirely different things when you are talking about a transformer(ballast).

PaulErik · 08/12/2007, 09:52 PM

With a magnetic pulse start, HQI or electronic ballast you must be careful testing the output side of the ballast. These ballasts can generate voltages as high as 6000 volts and will fry a standard volt meter / multi meter. You have to make sure the starting circuit/ignitor does not kick on while testing. You need specialized equipment or make a safety test rig to do it safely.

Why do you want to know the output voltage?

The output voltage will depend on the lamp. The ballast limits current and the lamp sets the operating/arc voltage. With a pulse start ANSI M137/M152 the voltage will be approximately 130 volts at full brightness/operation.

booker · 08/12/2007, 09:55 PM

If you assume the bulb actually uses 175 watts, maybe someone can chime in here with actual usage, then an ammeter and Ohms law will get the info you desire.

J. Montgomery · 08/14/2007, 08:43 AM

Quote:

Originally posted by PaulErik
Why do you want to know the output voltage?

I've recently been switching MH bulbs. A buddy let me borrow an XM 20k bulb, he remarked that it didn't look as bright as he expected. We were wondering if maybe the ballast wasn't running at full strength.

My friend is overdriving a Radium bulbs with a HQI ballast, which he says runs his 250W bulb at 330W . . . thats how we came upon the question of, "I wonder how much voltage is being applied to the bulbs?"

Entropy · 08/14/2007, 09:02 AM

What ballast is he using? It is impossible to deliver 330w of power to a bulb from a 250w ballast. You can only deliver input wattage minus efficiency loss. Which is usually about %10 loss (or more). This is why a lot of 250w ballasts use more input power than 250w.

PaulErik · 08/14/2007, 01:49 PM

With a magnetic ballast the output voltage does not determine if the lamp is overdriven or under driven.

The ballast regulates/limits current to the lamp. Once the lamp reaches equilibrium the lamp will determine the operating voltage. In order to overdrive or under drive a metal halide lamp with a magnetic ballast you need to use a ballast with a different drive/operating current.

The Radium 250-watt 20,000K lamp will not be overdriven on a HQI (ANSI M80) ballast. The Radium is designed to the same electrical specification. The Radium is actually rated at 270-watts nominal. The HQI ballast limits the current to the same level but the lamp is designed to operate at a higher operating arc voltage. Allowing the lamp to operate at a higher wattage. http://www.radium.de/e/produkt_detai...te_template=15

You can not measure what the ballast draws and assume the lamp is driven at that wattage. Itâ€™s a little more complicated. The ballast has losses (wastes powers). In order to know the true lamp wattage you must know the power factor, nominal arc voltage and nominal arc current.

You need specialized equipment to take these readings with a magnetic HQI or pulse start ballast because of the high voltage ignitor. Here at work we use a specially designed stand alone superimposed type starting circuit. This allows you to take readings safely between the ballast and the starting circuit while the lamp is in the circuit operating.

If you are worried the ballast is not driving the lamp properly you can check the ballast to make sure it is operating correctly. You will need a multi meter. The method used to test a ballast will vary by the ballast type. To test a magnetic pulse start ballast requires some rewiring to take readings. If you are not comfortable working with electrical wiring I would not recommend performing any testing.

With a magnetic pulse start Constant Wattage Autotransformer (CWA) ballast you can check the capacitor with a multi meter. With the capacitor disconnected you can take a reading and if it is correct (within specification) then the ballast coil should be checked. The capacitor in this ballast type (CWA) is used to regulate lamp current along with the ballast and for power factor correction. If the capacitor is not within specification this will affect lamp operation.

You can check the ballast coil. With this type of ballast it is extremely important to disconnect the ignitor from the ballast circuit. To disconnect the ignitor you must disconnect the X2 (Common) wire from the ignitor and cap off the wires. With the capacitor in place and the ballast powered on you can measure the output voltage from the output leads with a volt meter / multi meter. This is done without a lamp installed. This will give you an Open Circuit Voltage (OCV) reading. The ballast specification for that ballast or the ballast label will have the correct OCV value listed. With an ANSI M137/M152 CWA ballast the OCV will generally be around 240-350 volts AC.

Usually if the capacitor and the ballast OCV is within specification the ballast is functioning correctly.

J. Montgomery · 08/14/2007, 01:59 PM

. . . well, that does answer my question. No, I'm not going to be attempting to measure the voltage coming from my ballast!

Thanks, guys.

08/12/2007, 07:48 PM	#1
J. Montgomery Mouth Pipetting Join Date: Aug 2006 Location: Charlottesville, VA Posts: 6,278	Measuring Voltage from Ballast? Someone asked me what voltage my ballast was running my bulbs (Blue Wave II: 175W dual magnetic pulse start: M137). I have a voltage meter, is there a safe way that I can measure the voltage from the ballast without severely injuring myself? __________________ Josh

08/12/2007, 09:18 PM	#3
israelnajar Registered Member Join Date: Sep 2006 Location: 5000 Feet Posts: 1,007	This plus ohms law __________________ I would never do such a thing unless you would already have been going to do that!

08/14/2007, 09:02 AM	#8
Entropy Texas Reefer Join Date: May 2003 Location: Round Rock, TX Posts: 13,656	What ballast is he using? It is impossible to deliver 330w of power to a bulb from a 250w ballast. You can only deliver input wattage minus efficiency loss. Which is usually about %10 loss (or more). This is why a lot of 250w ballasts use more input power than 250w. __________________ Rich Overton 150G cube FOWLR, 30g sump, ReefKeeperII, 3x Koralia 1400's, QuiteOne 3000, Reef Octopus DNWB150, 4x 30w Par38 LED. Current Tank Info: 36x36x27 150g

08/14/2007, 01:59 PM	#10
J. Montgomery Mouth Pipetting Join Date: Aug 2006 Location: Charlottesville, VA Posts: 6,278	. . . well, that does answer my question. No, I'm not going to be attempting to measure the voltage coming from my ballast! Thanks, guys. __________________ Josh

08/12/2007, 08:58 PM	#2
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	Only to the ballast not from the ballast. The ballast is a transformer and amplifies the power tremendously to power the bulbs.

08/12/2007, 09:37 PM	#4
AZDesertRat Moved On Join Date: Jan 2002 Location: NW Phoenix Posts: 16,621	That and Ohms law are fine on the incoming side. A ballast can put out hundreds or even thousands of volts depending on the application. Input and output are two entirely different things when you are talking about a transformer(ballast).

08/12/2007, 09:52 PM	#5
PaulErik Premium Member Join Date: Dec 2000 Location: North Charleston, SC Posts: 1,703	With a magnetic pulse start, HQI or electronic ballast you must be careful testing the output side of the ballast. These ballasts can generate voltages as high as 6000 volts and will fry a standard volt meter / multi meter. You have to make sure the starting circuit/ignitor does not kick on while testing. You need specialized equipment or make a safety test rig to do it safely. Why do you want to know the output voltage? The output voltage will depend on the lamp. The ballast limits current and the lamp sets the operating/arc voltage. With a pulse start ANSI M137/M152 the voltage will be approximately 130 volts at full brightness/operation.

08/12/2007, 09:55 PM	#6
booker Registered Member Join Date: May 2007 Posts: 31	If you assume the bulb actually uses 175 watts, maybe someone can chime in here with actual usage, then an ammeter and Ohms law will get the info you desire.

08/14/2007, 01:49 PM	#9
PaulErik Premium Member Join Date: Dec 2000 Location: North Charleston, SC Posts: 1,703	With a magnetic ballast the output voltage does not determine if the lamp is overdriven or under driven. The ballast regulates/limits current to the lamp. Once the lamp reaches equilibrium the lamp will determine the operating voltage. In order to overdrive or under drive a metal halide lamp with a magnetic ballast you need to use a ballast with a different drive/operating current. The Radium 250-watt 20,000K lamp will not be overdriven on a HQI (ANSI M80) ballast. The Radium is designed to the same electrical specification. The Radium is actually rated at 270-watts nominal. The HQI ballast limits the current to the same level but the lamp is designed to operate at a higher operating arc voltage. Allowing the lamp to operate at a higher wattage. http://www.radium.de/e/produkt_detai...te_template=15 You can not measure what the ballast draws and assume the lamp is driven at that wattage. Itâ€™s a little more complicated. The ballast has losses (wastes powers). In order to know the true lamp wattage you must know the power factor, nominal arc voltage and nominal arc current. You need specialized equipment to take these readings with a magnetic HQI or pulse start ballast because of the high voltage ignitor. Here at work we use a specially designed stand alone superimposed type starting circuit. This allows you to take readings safely between the ballast and the starting circuit while the lamp is in the circuit operating. If you are worried the ballast is not driving the lamp properly you can check the ballast to make sure it is operating correctly. You will need a multi meter. The method used to test a ballast will vary by the ballast type. To test a magnetic pulse start ballast requires some rewiring to take readings. If you are not comfortable working with electrical wiring I would not recommend performing any testing. With a magnetic pulse start Constant Wattage Autotransformer (CWA) ballast you can check the capacitor with a multi meter. With the capacitor disconnected you can take a reading and if it is correct (within specification) then the ballast coil should be checked. The capacitor in this ballast type (CWA) is used to regulate lamp current along with the ballast and for power factor correction. If the capacitor is not within specification this will affect lamp operation. You can check the ballast coil. With this type of ballast it is extremely important to disconnect the ignitor from the ballast circuit. To disconnect the ignitor you must disconnect the X2 (Common) wire from the ignitor and cap off the wires. With the capacitor in place and the ballast powered on you can measure the output voltage from the output leads with a volt meter / multi meter. This is done without a lamp installed. This will give you an Open Circuit Voltage (OCV) reading. The ballast specification for that ballast or the ballast label will have the correct OCV value listed. With an ANSI M137/M152 CWA ballast the OCV will generally be around 240-350 volts AC. Usually if the capacitor and the ballast OCV is within specification the ballast is functioning correctly.