poobah said:
A good MOV should be UL approved & listed against fire hazard......however where I live the AC and electric storms are so rough that they don't get a chance to work.
I was forced to use a hard bi directional transorb and a low value non induct power resistor to avoid persistent fuse blowing. and up goes the component count....Most component vendors have several types.
richj
Hi poobah,
I use MOV's on a regular basis. UL/ CSA approved parts. Sometimes they explode, but when lightning strikes - all bets are off anyway. They typically short and blow the fuse.
I have numerous cases where these have saved equipment or substantially limited the damage. I have never had one fail in normal use without a "power event" occurring. I highly recommend their use. The use of MOV's also extends power switch life by clamping the voltage when the power is turned off. The switch contacts do not arc anymore.
-Chris
I use MOV's on a regular basis. UL/ CSA approved parts. Sometimes they explode, but when lightning strikes - all bets are off anyway. They typically short and blow the fuse.
I have numerous cases where these have saved equipment or substantially limited the damage. I have never had one fail in normal use without a "power event" occurring. I highly recommend their use. The use of MOV's also extends power switch life by clamping the voltage when the power is turned off. The switch contacts do not arc anymore.
-Chris
Hey Chris,
Yeah I put em on stuff too... cheap and they'll take a good whack (mostly solar stuff... lighning rods
). In this application I think getting "hit" is going to be a regularity rather than a rarity. I had to replace 640 of these once because someone used them in place of TVS. Just a good idea to calculate the energy and look at the charts is all I'm sayin'. They finally have charts now... cuz the TVS people took their business.
Yeah I put em on stuff too... cheap and they'll take a good whack (mostly solar stuff... lighning rods
). In this application I think getting "hit" is going to be a regularity rather than a rarity. I had to replace 640 of these once because someone used them in place of TVS. Just a good idea to calculate the energy and look at the charts is all I'm sayin'. They finally have charts now... cuz the TVS people took their business.
Chris,
AMOF, most technicians I've known are better about putting in the right goodies than engineers! So... you read the data, eh?
I went through the MOV nightmare in '95. I nearly had to hurt an engineer from HARRIS (I made him come to the jobsite in the secret deserts of California) before he would "come clean" and admit that MOV's are "consumable".
I'll shutup... we're jackin dhaens thread. -
AMOF, most technicians I've known are better about putting in the right goodies than engineers! So... you read the data, eh?
I went through the MOV nightmare in '95. I nearly had to hurt an engineer from HARRIS (I made him come to the jobsite in the secret deserts of California) before he would "come clean" and admit that MOV's are "consumable".
I'll shutup... we're jackin dhaens thread. -
Hi Poobah,
The link was dead. Found some stuff on the home page. I have no clue what you were indicating. But, yes MOV's once activated need to be replaced.
Most tech's do not have any clue. Many do, and those are the ones that engineers will take the time to work with. Anything else would be a waste of time.
Tell me about your nightmare. Sounds interesting. New thread on MOV's?
-Chris
The link was dead. Found some stuff on the home page. I have no clue what you were indicating. But, yes MOV's once activated need to be replaced.
Most tech's do not have any clue. Many do, and those are the ones that engineers will take the time to work with. Anything else would be a waste of time.
Tell me about your nightmare. Sounds interesting. New thread on MOV's?
-Chris
Tomorrow Chris,
You know hobby or not... as much money as people wrap up in their toys a thread on transient protection and suppression would be cool.
Some of this might have bearing on the $1500 power cords too (I hope nobody selling these is paying for the server and the PHP/SQL dudes), why you don't need them and how $15 will do 100 times as much...
BTW... what am I doing wrong? I cant get long URL's to post right.
Cheers,
You know hobby or not... as much money as people wrap up in their toys a thread on transient protection and suppression would be cool.
Some of this might have bearing on the $1500 power cords too (I hope nobody selling these is paying for the server and the PHP/SQL dudes), why you don't need them and how $15 will do 100 times as much...
BTW... what am I doing wrong? I cant get long URL's to post right.
Cheers,
MOV's
Well that has raised an interesting topic. After a little research I can confirm that they are indeed "consumable".
When used in a typical application as a surge protector a typical MOV can tolerate 1000 surges of 3000 amperes or 100,000 surges of 100 amperes.
In the intended application, as a kick-back snubber, I would guestimate the surge to be under 1 amp. Working on just the last figure rather than the trend, I expect the MOV to be consumed, not before 10^10 surges on. Even if I am several magnitudes out in the calculation, it will long outlast me, as I am also "consumable"
Well that has raised an interesting topic. After a little research I can confirm that they are indeed "consumable".
When used in a typical application as a surge protector a typical MOV can tolerate 1000 surges of 3000 amperes or 100,000 surges of 100 amperes.
In the intended application, as a kick-back snubber, I would guestimate the surge to be under 1 amp. Working on just the last figure rather than the trend, I expect the MOV to be consumed, not before 10^10 surges on. Even if I am several magnitudes out in the calculation, it will long outlast me, as I am also "consumable"
Good for you dhaen! My only wish was that you would "run the numbers"
3000 AMPS!!! I have had at least 4 "outlet strips" (6 to 1 AC adapters) explode for me. Makes you think about how bad the AC line really is.
DIYers don't die... they only get a new job... repairing the Devil's
10,000 WATT SE (heat failures).
3000 AMPS!!! I have had at least 4 "outlet strips" (6 to 1 AC adapters) explode for me. Makes you think about how bad the AC line really is.
DIYers don't die... they only get a new job... repairing the Devil's
10,000 WATT SE (heat failures).
All,
Take a look at the level control at the amp's I/P. If a precision stepped attenuator is used as the grid leak resistor of the inverting triode, the low 10 KOhm I/P impedance inhereted from "El Cheapo" can be eliminated. It makes NO sense to put controls that cost as much as the entire amp into a LOW budget project. This project is more about good sound and less about pinching pennies.
A high precision resistance is needed in order for the filters at the I/Ps of the 2 channels to have an "identical" turn over frequency.
Take a look at the level control at the amp's I/P. If a precision stepped attenuator is used as the grid leak resistor of the inverting triode, the low 10 KOhm I/P impedance inhereted from "El Cheapo" can be eliminated. It makes NO sense to put controls that cost as much as the entire amp into a LOW budget project. This project is more about good sound and less about pinching pennies.
A high precision resistance is needed in order for the filters at the I/Ps of the 2 channels to have an "identical" turn over frequency.
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