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Does an AVR or surge (spike) suppressor really protect from voltage fluctuations???

AVR  means Automatic Voltage Regulation.

What it does is to regulate the mains voltage within a limited range. In the case of your UPS, it boost +12% when the incoming voltage is too low. Let’s say the incoming voltage is at 200 volts, the output then goes to 224Volts, +12% of 200 volts, which is still acceptable for most UPSs. When the UPS output reaches let’s say, 230V with the boost mode on, then the UPS sends a command to a component called relay so that the +12% compensation is turned off.

Basically the voltage regulation is a series of power transformers, it can either be step-up transformers or a step-down transformers  They basically do the same thing a 220V to 110V step-down transformer does, or a step-up transformer does, when it gets 110V and transforms to 220V. The UPS senses the incoming voltage and commands a series of relays  to select a different transformer output or “tap”, as they call it.

An automatic voltage regulator can only work within a limited range. Their “taps” are at a fixed rate lets say, +10volts. If the UPS have a 12% voltage trimming option and the incoming voltage reaches 270 Volts, it can only trim 12% of that, which will result in 237 Volts.

Voltage regulator transformer can have as many “taps” as its developer wants, but it makes the unit much heavier, it wastes more energy and generates more heat. It doesn’t matter if the AVR has four “taps” or sixteen taps, it is still slow for suppressing voltage surges
Surge suppression is basically made to protect against high energy and fast rising surges or spikes that can be caused by lightning, electric motors being turned on or turned off, etc. Surges are essentially fast rising spikes and voltage swells are slow rising and low energy in nature. Surge suppression can in some cases reduce voltage swells, but this is not its main purpose.
Surge protection is basically comprised of a component called MOV – Metal Oxide Varistor.

An MOV works at diverting surges to ground. When operating at its nominal voltage, or the mains voltage, the varistor acts like a resistor with its resistance tending to the infinite, so it does not conduct electricity to ground at this state. When there is a fast surge, it instantaneously reacts (in nanoseconds) by decreasing its internal resistance, allowing the excess energy to flow to ground.

The voltage regulator cannot act as fast as an MOV for suppressing high power and fast rising surges and would not be capable of that because of the nature of a power transformer. High energy surges must be diverted to ground and power transformers do not do that. Compared to the speed of an MOV, the voltage regulator is like a turtle.

There are some disadvantages regarding the use of MOVs for suppressing voltage swell. MOVs degrade very fast if frequent voltage swell are imposed to it, it gets too hot and it’s internal chemistry degrades. MOVs are made to react fast and come back to it’s initial state very quickly as well, which happens when a power surge occurs. That’s why manufactures of surge protective devices use an MOV that only triggers itself when the voltage is much higher than the mains voltage. If the MOV starts to conduct too early, it will degrade itself very quickly and on all power grids a relatively high number of fast duration swells, do happen

What an MOV doesn’t do…

An MOV does not provide equipment with complete power protection. In particular, a MOV device provides no protection for the connected equipment from sustained over-voltages that may result in damage to that equipment as well as to the protector device.

An  MOV provides no equipment protection from inrush current surges (during equipment start-up), from over current (created by a short circuit), or from voltage sags (also known as a brownout); it neither senses nor affects such events.

Susceptibility of electronic equipment to these other power disturbances is defined by other aspects of the system design, either inside the equipment itself or externally by means of  a circuit which typically consists of a voltage-sensing circuit and a relay for disconnecting the AC input when the voltage reaches a danger threshold. See OVCD).

In nut shell…

The AVR and the surge suppression solve two different problems. They’re complimentary technologies but do  not ensure total power protection.

The AVR can adjust the voltage of the line within a limited range to compensate for the voltage being too high or too low. However, the AVR does not respond quickly enough or have wide enough compensation to handle surges.

Surge protection is capable of putting huge surge voltages into ground very quickly, but won’t adjust the long-term voltage of the line as the AVR does.

Both however are ineffective against sustained high voltages. in neutral open condition , they themselves will need protection.

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Also see:

some facts about over voltage

Over Voltage cut off Device

How to protect your equipments from extreme power fluctuations



Effect of Supply variations on different types of Equipments

Some Facts about overvoltage

Over voltage problems are the most frequent the most overlooked and neglected. Many times equipment failure, downtime, software and data corruption, are the result of a problematic supply of power.  There is also a common problem with describing power problems in a standard way. We have tried to list out some of the common facts about over voltage issues

  1. Overvoltage, and its destructive effects, are well known but are often not recognized or understood.
  2. Little is documented in terms of its magnitude and frequency.
  3. It is difficult to identify, due to its sporadic nature, and often comes and goes undetected.
  4. Because of all the above, its existence is sometimes denied.
  5. Equipment failures due to overvoltage are often misperceived as defective equipment.
  6.  Power companies do not deny its existence; but they do not publish or otherwise inform the users that it exists, or warn users of potential periods in which it may occur.
  7. Power fluctuations are also caused due to in–line equipment. Viz. Motor during its starting period draws heavy current due to which voltage drops causing imbalance and over voltage somewhere else.
  8. With very few exceptions, electrical power distribution systems are inadequate to provide voltage within acceptable limits to all users at all times.
  9. Power companies cannot prevent overvoltage because they can only react to its existence, usually in response to customer (user) complaints about failing appliances, etc.
  10. The time of response can vary widely (anywhere between one minute and weeks) depending on many variables in the distribution system.
  11. Overvoltage can occur at any time, due to many factors, but is most likely to occur during certain periods such as fast changing high load demands, as seen during severe cold weather periods.
  12. Power companies are mandated by law to provide service without overvoltage.
  13. Power companies are not held accountable by any regulation authority for overvoltage.
  14.  Power companies will sometimes reimburse damage costs due to overvoltage if proof is provided by the complainant.
  15.  Overvoltage can only be proved by the use of a voltage recorder.
  16.  Some power companies offer overvoltage insurance to users.
  17.  Over voltage events are misperceived to be equipment failures leading to their replacement with other brands that do not have overvoltage protection and essentially mask the effects of overvoltage which can lead to inevitable catastrophic failures.

Also see:

  1.  OVCD- Over Voltage Cut-off Device
  2. How does a Servo Controlled Voltage Stabilizer work?
  3. Product breakdown management
  4. Protect your Equipment from harmful power fluctuations..
  5. Give reliability to your UPS systems in high fluctuation areas. OVCD solves your servicing woes!!!
  6. Protect your electronics

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