wiigelec
Member
- Location
- Red Desert
What fuses are you blowing? Fuses blow on over-current, not over-voltage...
124.5 volts single phase
- Thread starter dcooper
- Start date
- Status
What fuses are you blowing? Fuses blow on over-current, not over-voltage...
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110408-2202 EST
wiigelec:
Fuses blow (open up) on excessive i^2*t. For most any load when you increase the input voltage you also increase the input current. When there is a large input transient voltage there is likely a sufficient i^2*t to open the fuse. If the overvoltage is moderately large, then it will need to last longer to blow the fuse.
What is characteristic of the problem that has been stated is that incandescent bulbs had a short life time, and that some equipment, probably simultaneously, had fuses blow.
Incandescent lamp bulbs do not have shortened life times by low voltage, but by high voltage. Fuse blowing at low voltage on some loads is a possibility. But since lamps also burned out the likely cause of these problems is some sort of overvoltage condition. Maybe very high and very short, or maybe moderate overvoltage but much longer.
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wiigelec:
Fuses blow (open up) on excessive i^2*t. For most any load when you increase the input voltage you also increase the input current. When there is a large input transient voltage there is likely a sufficient i^2*t to open the fuse. If the overvoltage is moderately large, then it will need to last longer to blow the fuse.
What is characteristic of the problem that has been stated is that incandescent bulbs had a short life time, and that some equipment, probably simultaneously, had fuses blow.
Incandescent lamp bulbs do not have shortened life times by low voltage, but by high voltage. Fuse blowing at low voltage on some loads is a possibility. But since lamps also burned out the likely cause of these problems is some sort of overvoltage condition. Maybe very high and very short, or maybe moderate overvoltage but much longer.
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Electric-Light
Senior Member
As for incandescent lamps, put it on a dimmer. Dimmers do not close fully like a switch, so even when set to maximum brightness, it will drop a few volts RMS. (you'll have to use true RMS meter to measure the voltage at lamp). This will correct premature burn-out.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110408-2349 EDT
Electric-Light:
Why do you make the statement --- a true RMS meter is required?
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Electric-Light:
Why do you make the statement --- a true RMS meter is required?
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Electric-Light
Senior Member
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110409-0753 EDT
Electric-Light:
A full-wave rectified average reading calibrated in RMS on a sine wave meter (a Fluke 27 or Simpson 260, 270) will read the same as a true RMS on a sine-wave voltage, at least within its tolerance limit.
On most non-sine wave signals the readings may be somewhat different, and others quite different.
Your objective in suggesting the use of a voltmeter before and after the dimmer was to show that the bulb had a somewhat lower voltage than line voltage when the dimmer was in its full on position. Both the average reading and true RMS meters will do this.
The primary important reason for using a true RMS meter instead of an average reading type is to estimate the heating effect in a resistance. If this is not the goal, then either type meter might be satisfactory for the purpose.
In the application of the incandescent light bulb with the dimmer if you were trying to estimate the the light intensity of the light, then the RMS voltage is important. But if you are simply trying to show that the voltage is lower, then either the average reading or RMS is satisfactory. A peak reading voltmeter would not be a satisfactory tool to use for your experiment at dimmer full on as it would only show the TRIAC voltage drop, a volt or two.
Following is a comparison of an average reading, Fluke 27, and a true RMS, Beckman 4410, on the output side of a dimmer:
4410 .......... 27
123.4 ...... 123.6 ....... linput ine voltage to the dimmer
117.9 ...... 107.0 ....... output of dimmer full on
064.5 ...... 039.9 ....... some sort of middle position
027.6 ...... 012.5 ....... minimum position
A Simpson 270 is close to the same as the Fluke 27.
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Electric-Light:
A full-wave rectified average reading calibrated in RMS on a sine wave meter (a Fluke 27 or Simpson 260, 270) will read the same as a true RMS on a sine-wave voltage, at least within its tolerance limit.
On most non-sine wave signals the readings may be somewhat different, and others quite different.
What does the word voltage mean here? It will report a voltage although different than what an RMS meter would report.
Your objective in suggesting the use of a voltmeter before and after the dimmer was to show that the bulb had a somewhat lower voltage than line voltage when the dimmer was in its full on position. Both the average reading and true RMS meters will do this.
The primary important reason for using a true RMS meter instead of an average reading type is to estimate the heating effect in a resistance. If this is not the goal, then either type meter might be satisfactory for the purpose.
In the application of the incandescent light bulb with the dimmer if you were trying to estimate the the light intensity of the light, then the RMS voltage is important. But if you are simply trying to show that the voltage is lower, then either the average reading or RMS is satisfactory. A peak reading voltmeter would not be a satisfactory tool to use for your experiment at dimmer full on as it would only show the TRIAC voltage drop, a volt or two.
Following is a comparison of an average reading, Fluke 27, and a true RMS, Beckman 4410, on the output side of a dimmer:
4410 .......... 27
123.4 ...... 123.6 ....... linput ine voltage to the dimmer
117.9 ...... 107.0 ....... output of dimmer full on
064.5 ...... 039.9 ....... some sort of middle position
027.6 ...... 012.5 ....... minimum position
A Simpson 270 is close to the same as the Fluke 27.
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wiigelec
Member
- Location
- Red Desert
Depends on the magnitude/duration of the transient and the type of fuse...
...which is why I was inquiring as to the location, type, and rating of the affected fuses...
...ie are we talking about line fuses or control fuses?
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
My theory: cheap Chinese incandescent bulbs. There are no incandescent bulb mfrs left in the US and a lot of stores have resorted to alternate suppliers because of the CFL issue now. Quality has gone to hell in a hand basket. I stocked up on GE bulbs when I heard the last factory shut down a few months ago but my mother buys Chinese bulbs at the Dollar Store, they don't last a month.
Wait, what? A fuse on a GAS water heater? I have a gas water heater, there is no electricity going to it. Are you sure they aren't messing with you? Or was it maybe an Instant Water Heater and the 120V is for the controls? Hard to imagine that causing a fuse to blow unless there was some sort of catastrophic failure, in which case the fuse sacrificed itself in the line of duty and should be buried with honors!
What size fuse and was it the right size for the dryer motor? Was it a TD fuse or an non-TD? It had to be a TD fuse, the only thing the 120V is for on a dryer is the tumbler motor (and controls).
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Electric-Light
Senior Member
And that is why I said you need true RMS. That's big enough of a difference to be clearly misleading that you might as well not bother measuring it and take what I said for what its worth. When you're trying to prove ~5v voltage drop and you're seeing an error of 11v, why even bother measuring?
Last edited:
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110409-1913 EDT
Larry:
A Weston-D'Arsonval movement includes an approximately uniform and constant magnetic field in which a moving coil is supported and spring loaded so that torque from the spring increases with rotation. A Simpson 260 has this type of meter movement.
Thus, a steady DC current thru the coil will produce a deflection of the needle proportional to the current thru the coil. Because this is a mechanical system with mass it also performs an averaging function for rapidly varying current.
If an equally balanced AC waveform, above a frequency determine by the mechanics of the meter, is applied to this meter, then the meter will read zero.
This is not an AC RMS meter. It can be part of an RMS meter in either of two ways. The first is to combine it with a thermocouple and a current carrying wire to form a hot wire ammeter. The second way is connect it to some RMS electronic circuit.
http://www.engineersedge.com/instrumentation/electrical_meters_measurement/darsonval_movement.htm
http://physics.kenyon.edu/EarlyAppa...nval_Galvanometer/DArsonval_Galvanometer.html
When the Weston-D'Arsonval movement is combined with a half or full wave rectifier it becomes an average reading AC meter. These are usually calibrated on a sine wave to read the RMS value of that sine wave.
There are moving coil true RMS meters. These are called electrodynamometer movement. The DC field of the permanent magnet is replaced with fixed coils that are in series with the moving coil. This produces a torque proportional to the square of the current, The meter movement produces the averaging function, and the non-linear scale performs the sq-root function. Another true RMS meter with a moving pointer is an electrostatic meter.
See "Basic Electrical Measurements", by M. B. Stout for a discussion on some of these instruments.
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Larry:
A Weston-D'Arsonval movement includes an approximately uniform and constant magnetic field in which a moving coil is supported and spring loaded so that torque from the spring increases with rotation. A Simpson 260 has this type of meter movement.
Thus, a steady DC current thru the coil will produce a deflection of the needle proportional to the current thru the coil. Because this is a mechanical system with mass it also performs an averaging function for rapidly varying current.
If an equally balanced AC waveform, above a frequency determine by the mechanics of the meter, is applied to this meter, then the meter will read zero.
This is not an AC RMS meter. It can be part of an RMS meter in either of two ways. The first is to combine it with a thermocouple and a current carrying wire to form a hot wire ammeter. The second way is connect it to some RMS electronic circuit.
http://www.engineersedge.com/instrumentation/electrical_meters_measurement/darsonval_movement.htm
http://physics.kenyon.edu/EarlyAppa...nval_Galvanometer/DArsonval_Galvanometer.html
When the Weston-D'Arsonval movement is combined with a half or full wave rectifier it becomes an average reading AC meter. These are usually calibrated on a sine wave to read the RMS value of that sine wave.
There are moving coil true RMS meters. These are called electrodynamometer movement. The DC field of the permanent magnet is replaced with fixed coils that are in series with the moving coil. This produces a torque proportional to the square of the current, The meter movement produces the averaging function, and the non-linear scale performs the sq-root function. Another true RMS meter with a moving pointer is an electrostatic meter.
See "Basic Electrical Measurements", by M. B. Stout for a discussion on some of these instruments.
.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
110409-2128 EDT
Electric-Light:
The point I got from your original statement was that you wanted one to understand that for a typical dimmer that the output voltage at the dimmer full on position was less than at line voltage. That can be shown with either a true RMS meter or an average reading meter. In that original statement there was no indication that a value that would directly indicate the heating effect was necessary as proof. To prove the voltage would be lower did not require someone to go find a true RMS meter for the experiment if they did not happen to have one.
Further the experiment can be run without a meter.
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Electric-Light:
The point I got from your original statement was that you wanted one to understand that for a typical dimmer that the output voltage at the dimmer full on position was less than at line voltage. That can be shown with either a true RMS meter or an average reading meter. In that original statement there was no indication that a value that would directly indicate the heating effect was necessary as proof. To prove the voltage would be lower did not require someone to go find a true RMS meter for the experiment if they did not happen to have one.
Further the experiment can be run without a meter.
.
kwired
Electron manager
- Location
- NE Nebraska
Gas water heaters with draft motor and electric ignition and associated controls are becoming more common. They usually are 120 volt, similar in operation to ignition controls on a gas furnace.
Electric-Light
Senior Member
Here's what logging looks like on Fluke after download:
It's set for 5 min interval. Each bar represents five minute and top part is the maximum observed during 5 min, bottom is minimum, and the center bar is mean average.
This is a long term average over 30 hours.
You can set at a pretty long interval and it will continously record the minimum and max. The meter continues to sample constantly and if there are deviations that exceeds the percentage you set from current reading, it will create dedicated entry under "events". The percentage can only be set from the computer using the software, so set it before you go to site.
It's set for 5 min interval. Each bar represents five minute and top part is the maximum observed during 5 min, bottom is minimum, and the center bar is mean average.
This is a long term average over 30 hours.
You can set at a pretty long interval and it will continously record the minimum and max. The meter continues to sample constantly and if there are deviations that exceeds the percentage you set from current reading, it will create dedicated entry under "events". The percentage can only be set from the computer using the software, so set it before you go to site.
kilewatt2002
Member
- Location
- washington state
Its not your neurtral
Its not your neurtral
I would put a graph on that service for atleast 72 hours to see what is going on with the supply
Look around area see what the demand is
In Mississippi I once had a similar problem discovered that I was getting power surges due to huge power draws coming at the same time of day
Asking the power company for help is a moot issue as you have found out
Contact me at kilewatt2002@ yahoo.com if you need further help I have a couple other ideas.
Are thes things happening at the same time of day
Talk to neighboring bldgs see if they are having same problem
Its not your neurtral
I would put a graph on that service for atleast 72 hours to see what is going on with the supply
Look around area see what the demand is
In Mississippi I once had a similar problem discovered that I was getting power surges due to huge power draws coming at the same time of day
Asking the power company for help is a moot issue as you have found out
Contact me at kilewatt2002@ yahoo.com if you need further help I have a couple other ideas.
Are thes things happening at the same time of day
Talk to neighboring bldgs see if they are having same problem
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