Computer and electronic circuits

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aidan011408

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Will disconnecting the circuit under load (without turning off the breaker) damage computers or electronic equiptment? And if so please explain why?
 
Welcome to the forum, it is not necessary to turn off breaker to shed the load, but rather turn the load off. Second, if you unplug under a load, yes, it could create a spark, just like contacts opening, that can be hazardous to electronics.

And third,,,if it';s a MWBC, as stated above, and you break the neutral, be prepared to let some smoke fly
 
Switching off a computer without following a proper shutdown procedure can lead to loss of data. For any computer system that holds a serious amount of dsata, the value of the data outweighs the computers many times over.
 
aidan011408 said:
Will disconnecting the circuit under load (without turning off the breaker) damage computers or electronic equiptment? And if so please explain why?
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The main thing which cause to the electronic equipment is voltage variation. That is why TVSS mostly used to maintian the voltage level stable.
another exmaple of disconnecting is unplug your computer from socket. If is loptop nothing happens or if it is a Desktop computer without UPS it will turn off may cause damage your softwares and files.

If you disconnect circuit and creats sparks, than breaker will turn off as soon as spark creats.

Welcome to the forum
 
Clearifying the question!

Clearifying the question!

No it is not a MWBC. If you remove the wire from the breaker before turning it off.
 
brian john said:
How does a TVSS stabilize voltage? MInimize damage from impulses yes but under voltage or over voltage (depending on the clamping voltage)?
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it has alot of things please see below


A surge protector is an electronic device that limits transient overvoltages to a safe level, thus protecting equipment from damage or disruption. A surge protector may also be expressed using the following terms: SPD (Surge Protective Device), TVSS (Transient Voltage Surge Suppressor. An arrestor (used by utility companies and communication companies) is also a surge protector, but is typically employed in a different part of the electrical system than a surge protector.

A surge protector works by momentarily ?switching? from an open circuit mode into a low impedance mode. This low impedance mode diverts the surge current through the protector and in doing so, limits the overvoltage to a safe level. When the surge event is over, the protector returns to its open circuit mode, ready for the next event.

A metal oxide varistor is a voltage-dependent, semiconductor-based, variable resistor. Electrically, it appears as an open circuit across a power line until its voltage threshold is reached. When this occurs, the varistor will instantaneously change from a high resistance mode (open circuit) to a low resistance mode (short circuit), thus conducting currents through it. Once the overvoltage event has passed and the voltage returns to below the threshold level of the varistor, it will return to an open circuit again until the next overvoltage event that exceeds its threshold occurs.


Although surge protectors are simple to install, a qualified electrician should be used for all hardwired protectors. This will ensure that a safe and effective installation is achieved and all local codes are met. Installation is either ?parallel? or ?series?. These are the two types of protectors available.

Series installed protectors are typically used at the equipment level, either right in front of, or within the equipment they are protecting. These protectors have an ?input? and an ?output? whereas parallel protectors do not. A common example of a series connected protector is a surge protected strip. Since they are connected in series with the equipment, they conduct load current. It is also common for a series AC protector to contain a EMI/RFI noise filter. This filtering is useful when it is right in front of the equipment to filter out noise generated by other loads.

Parallel protectors do not conduct load current and simply ?tap? into the power system via a circuit breaker. Parallel protectors are commonly used where large surge energies exist. They?re used on service entrance panels and switchgear, plus branch and local panels. There are a number of reasons why parallel protectors are very popular. They have proven reliability/effectiveness, and are easy to install. And since parallel connected protectors do not have to support system load currents, they are relatively small and not costly. Parallel connected protectors are the staple for all AC applications, except the aforementioned small equipment level applications.

A UPS is not a surge protector. A UPS (uninterruptible power supply) maintains AC power to the building should the utility have an outage or a brownout scenario. Typically a surge protector is installed ahead of the UPS to protect the sensitive line monitoring circuits at the front end of the UPS.
A surge protector is not a UPS. A surge protector will not maintain AC voltage to the loads should a voltage outage or reduction occur.

The Ipk rating of a surge protector is the protector?s maximum surge current rating. It is typically published as per phase rating (i.e. 160,000A/Phase), but it can also be expressed as a per mode rating (i.e. 80,000A Line-Neutral, 80,000A Line-Ground). This rating is a critical parameter with regard to the application on surge protective devices. This parameter is usually expressed as an 8 x 20 microsecond current pulse, which is the accepted industry standard waveform used to test and compare surge protective devices.
An 8 x 20 microsecond waveform is a current pulse whose parameters mimic the surge currents that can appear on a power system. Surge protector manufacturers use it to test and rate their products. It has a rise time of 8 microseconds and duration of 20 microseconds.

A circuit breaker used in series with a surge protector for the same reason a circuit breaker is used to protect a branch circuit, to prevent a fire. A circuit breaker is ?invisible? to a transient or surge so it will not open during most transient events. But should the surge protector start to draw large amounts of AC current (which is not normal operation of parallel AC surge protector), the breaker will open and disconnect the protector from the AC line. Fuses may also be used in series with the surge protector to achieve the same level of safety, but we find that circuit breakers have better transient withstand capacity.
 
brian john said:
You did not explain this statement.
Click to expand...


Originally Posted by Hameedulla-Ekhlas
The main thing which cause to the electronic equipment is voltage variation. That is why TVSS mostly used to maintian the voltage level stable.
Click to expand...

This is what I said. When a "TVSS mostly used to maintian the voltage level stable", I may have missed the word " in transient condition " but ofcourse everybody knows when we use TVSS.

I have already mentioned in the last post this " TVSS limits the overvoltage to a safe level". When something remains to its real condition, can we not call it stable?


Ok in another words,

suppose the voltage is 110 to 120 volts. when transients occurs, peak voltage level reaches several hundered volts. Eventhough, these pulese can be for a short time or microseconds but in that time they can cause hardware to malfuction. Specially when lightning strikes

A surge suppressor prevents the peak AC from going above a certain level. Can you not call it that TVSS maintains voltage level stable.


According to IEEE std.62.64
surge arrester: A protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its original status. It is capable of repeating these functions as specified. Is not explain stability?

metal-oxide surge arresters (MOSAs) designed to repeatedly
limit the voltage surges on 48 Hz to 62 Hz power circuits (>1000 V) by passing surge discharge current and automatically limiting the flow of system power current. Is not explain stability?

surge protectors for application on multiconductor and coaxial,
balanced or unbalanced, data, communications, and signaling circuits with voltages less than or equal to 1000 V rms, or 1200 V dc. These surge protectors are intended to limit voltage surges, current surges, or both. This limitation Is not explain stability?
 
100415-0816 EST

If you have a circuit with load current present and you pull the wire from a breaker or open this circuit in any other way (turn off breaker, open a switch, pull a plug out, etc.) there will be a high voltage produced across the point being opened resulting from the interruption of the current in an inductor. The more inductance in the circuit the more energy dissipated in the arc. Basic electrical theory.

.
 
Hameedulla-Ekhlas said:
This is what I said. When a "TVSS mostly used to maintian the voltage level stable", I may have missed the word " in transient condition " but ofcourse everybody knows when we use TVSS.

I have already mentioned in the last post this " TVSS limits the overvoltage to a safe level". When something remains to its real condition, can we not call it stable?

suppose the voltage is 110 to 120 volts. when transients occurs, peak voltage level reaches several hundered volts. Eventhough, these pulese can be for a short time or microseconds but in that time they can cause hardware to malfuction. Specially when lightning strikes

A surge suppressor prevents the peak AC from going above a certain level. Can you not call it that TVSS maintains voltage level stable.


According to IEEE std.62.64
surge arrester: A protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its origin. Is not explain stability?

?
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NO, NOT STABILITY OF VOLTAGE, stability has to do with maintaing voltage between predetermined levels. Yes you can minimize over voltage, but under voltage is an issue also.

If you try to tell a customer you are going to stabilize voltage with a TVSS, I bet you competitors will be on you in short order.
 
brian john said:
NO, NOT STABILITY OF VOLTAGE, stability has to do with maintaing voltage between predetermined levels. Yes you can minimize over voltage, but under voltage is an issue also.

If you try to tell a customer you are going to stabilize voltage with a TVSS, I bet you competitors will be on you in short order.
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I think you are confused between steady state and transient. I am not talking about the steady state voltage stability due to load ( over voltage, undervoltage, swell and sag ).
 
100515-2246 EST

Ham:

In the English language stable would mean without variation or at least with very little variation.

A TVSS (Transient Voltage Suppressor System) using something like an MOV may not do a lot of voltage limitation until about 2 to 3 times the nominal sine wave peak of the of the circuit being protected. In my opinion not much protection, but better than nothing. A back-to-back Zener diode transient suppressor has a much better characteristic curve.

From dictionary.com
sta?ble    /ˈsteɪbəl/ Show Spelled[stey-buhl] Show IPA
?adjective, -bler, -blest.
1. not likely to fall or give way, as a structure, support, foundation, etc.; firm; steady.
2. able or likely to continue or last; firmly established; enduring or permanent: a stable government.
3. resistant to sudden change or deterioration: A stable economy is the aim of every government.
4. steadfast; not wavering or changeable, as in character or purpose; dependable.
5. not subject to emotional instability or illness; sane; mentally sound.
6. Physics . having the ability to react to a disturbing force by maintaining or reestablishing position, form, etc.
7. Chemistry . not readily decomposing, as a compound; resisting molecular or chemical change.
8. (of a patient's condition) exhibiting no significant change.
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