We always learned this the expensive way.
How to SELECT a good SPD/TVSS?
The easy way of 'SELECTION' by 'The RULES OF THUMB'
Ask the supplier for the details of the product warranty:
LIMITED Warranty / UNLIMITED warranty?
Understand the "LIMITED" warranty - does the warranty cover damaged by LIGHTNING?
Period of warranty?
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Prefer the technical explanation? continue reading.............
Power Surge Protector Comparison
A true power surge protector comparison can be difficult...that is...if you really want to discuss product literature performance claims, in many cases, it is kind of comparing apples to oranges; Mercedes to Hyundai.
Do you know that none of the European suppliers tests to A1 ring waves because they have no frequency attenuation but only MOVs or spark gaps? Hard to compare no warranty statement to our 25-year free replacement for ANY electrical anomaly.
Performance claims can be tough to verify - especially if you don't have a surge generator to actually "test" the device via test protocols to validate its marketing claims.
After all, the performance claims are usually why you buy one product over another, isn't it? And when it comes down to it...don't you want to make sure your purchase performs as advertised?
Otherwise, why buy it?
A lesson to learn; Putrajaya spent millions of Ringgit to replace the damaged xxxx brand SPD after their 1 year warranty expired, instead of an investment to...
Reduce Electrical Maintenance Overhead
Reduce Down Time
Provide Catastrophic Protection
They now have to budget $millions for SPDs replacement and if the cost was the primary budget concern, the low initial cost has escalated into a higher yearly maintenance budget many times over the initial cost.
Surge protection devices with replaceable modules
Another surge protective device (SPD) design that is offered by several manufactures is known as a modular design. Modular designs include parts that can be replaced in the field. The most common replaceable module version is a metal box with replaceable surge components housed in a smaller 'plug in' plastic box.
In an SPD, the most commonly used surge suppression component is a MOV (metal oxide varistor). The MOV becomes a conductive component when the voltage across it exceeds a certain level known as the maximum continuous operating voltage (MCOV). Once the voltage exceeds MCOV, the current is allowed to flow through the MOV, which then passes the surge to the ground (Earth). For 'modular type' SPD, the MOVs are built into these plastic boxes that are available for easy field replacement if the internal MOV was damaged.
Some SPD manufacturers promote modular design to minimize their production costs. Plus, the use of modules creates an aftermarket replacement business for the SPD manufacturer. However, there are a number of potential technical flaws with modular designs.
• If one module is damaged, the remaining undamaged modules begin to compensate for the lost module, resulting in stress to the undamaged modules. This may lead to a second failure before the first module is replaced
• Many failures result in unacceptable damage to the interior of the metal box. Replacement of the modules is not sufficient to get the unit back to operating condition. These failures require replacement of the complete unit
• A damaged module may also cause unbalanced protection, in which the surge current is not equally shared across the MOVs. Most manufactures match the performance of the MOVs to achieve the specified performance. A new module will not be matched to the modules already in the product
• Many manufacturers of modular designs utilize “banana” pin connectors instead of low impedance bolt-on connections or leads. During high surge currents, the mechanical forces can rip these connectors out of their sockets. Many environmental conditions can degrade these connectors, as they rely solely on spring force to keep the connection
• Performance specifications can be misleading. Often the published suppression ratings are for the individual module and not for the entire SPD unit. Some manufacturers have designed modular products just for this reason. It is important to get the SVR (UL’s surge voltage ratings, markings required on all UL- listed products) ratings and surge current ratings for both the module and for the complete product
Another aspect to look at closely is theoretical surge current ratings. In order for accurate theoretical surge current ratings, there are two design criteria that must be considered.
1. Integrity of internal wiring
Low-end surge suppression devices may use small diameter circuit traces or wires, which cannot handle the rated surge current. Exposure to a large transient the modules can survive, but the total product cannot survive, leaving downstream loads unprotected. Most of the time these potential wiring deficiencies are inside of the SPD and hidden from the customer or specifying engineer.
2. Equal current sharing to each MOV
The SPDs internal wiring must ensure that each component is electrically balanced. In other words, a suppressor manufacturer must ensure the following performance criteria are met:
• Integrity of rated surge performance
• All surge paths must achieve the rated surge current
• Life expectancy
The total device must meet its lifetime performance rating. A possible result to SPDs that do not share surge current equally is a premature failure.
Premature failure is a common problem in modular designs since “newer” and “older” modules do not have the same MOV voltage, and therefore experience a reduction in surge current capacity.
3. Typical Protection Designs
Types of protection designs available in both Panel and integrated units:
Standard Clamp Circuitry
EMI/RFI Filters Circuitry
Sinewave Tracking Circuitry
Series Mode/Coil Circuitry
Devices available may incorporate one or more of the circuitry types to improve effectiveness - but again, the type and quality of components and a good design are key for a good SPD/TVSS.
Depending on unit design and other factors, performance and/or results will vary with different units...again regardless if the units in question are external unit TVSS or integrated units.
Please remember...Depending on how effective and dependable a protection unit you desire...you have different choices of "design" and components available.
Depending on the quality of design and components of the device you choose, the buyer should also determine the unit's overall effectiveness.
All surge protectors are not created equal. Although at times...marketing material performance claims seem to take you in that direction.
Some product marketing materials are accurate...some not so accurate...especially when placed in actual use.
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