A surge protector is an appliance designed to protect electrical devices from voltage spikes. A surge protector attempts to regulate the voltage supplied to an electric device by either blocking or by shorting to ground voltages above a safe threshold. The following text discusses specifications and components relevant only to the type of protector that diverts (shorts) a voltage spike to ground.
Many power strips have surge protection built-in; these are typically clearly labeled thus. However, sometimes power strips that do not provide surge protection are erroneously referred to as surge protectors.
Important specifications
Some specifications which define a surge protector for AC mains and some communication protection.
Clamping voltage — better known as the let-through voltage. This specifies what voltage will cause the metal oxide varistors (MOVs) inside a protector to conduct electricity to the ground line. A lower clamping voltage indicates better protection, but a shorter life expectancy. The lowest three levels of protection defined in the UL rating are 330 V, 400 V and 500 V. The standard let-through voltage for 120 V AC devices is 330 volts.
Joules — This number defines how much energy the surge protector can absorb without failure. A higher number indicates greater protection and longer life expectancy because the device will divert more energy elsewhere and will absorb less energy. More joules conducting the same surge current means a reduced clamping voltage. Generally, 200 joules is undersized protection since harmful voltage spikes are significantly larger than 200 joules. Better protectors start at 1000 joules and 50,000 amperes. If properly installed, for every joule absorbed by a protector, another 4 or 30 joules may be dissipated harmlessly into ground.
Response time — Surge protectors don't kick in immediately; a slight delay exists. The longer the response time the longer the connected equipment will be exposed to the surge. However, surges don't happen immediately either. Surges usually take around a few microseconds to reach their peak voltage and a surge protector with a nanosecond response time would kick in fast enough to suppress the most damaging portion of the spike .
Surge current in kiloamperes (see Joules above).
Standards — The surge protector may meet IEC 61643-1, BS6651, Telcordia TR-NWT-001011, ANSI / IEEE C62.xx, or UL1449. Each standard defines different protector characteristics, test vectors, or operational purpose. For example, a protector may obtain UL1449 approval even though it fails during testing. That standard tests only for fire hazards and other safety threats. Irrelevant to that approval test is whether the protector actually provides protection throughout testing. BS6651 and ANSI / IEEE C62.xx define what spikes a protector might be expected to divert. IEC only writes standards and does not certify any product to meet those standards. None of those standards say a protector will provide proper protection. Each standard defines what a protector should do or might accomplish.
没有评论:
发表评论