Re: UPS Neutral Help
Big John good question, I have been waiting for it. The “amp per phase” rating is simply the addition of the L-N modules plus the L-G modules. For example if you had a 150 KA module installed from L-N and another 150 KA installed from L-G the “amps per phase rating would be 300 KA. It makes a bold assumption the neutral and ground systems have equal impedance values and perfect current sharing between non-linear MOV modules can be accomplished. Rubbish!
It is important to understand that a “per phase” rating is not supported by any standard or legitimate rating. It is simply a theoretical value that cannot be verified through testing. NEMA LS1-1992 dictates that max surge current rating is provided on a “Per Mode” basis.
Joule is a meaningless rating. It has to be quantified. Is it 10-amps @ 10 minutes, 100-amps in one minute, or 100 KA in 10 microseconds? The answer depends on how the unit is designed, like what size fuses, wire, length, circuit impedance, etc. The maximum surge current rating is defined by NEMA LS1-1992 as “The maximum 8/20 microsecond surge pulse the SPD is capable of surviving on a single-impulse basis without more than 10 percent deviation of clamping voltage at a specified current”.
Here is a good example of a spec sheet and what I look for.
STANDARDS
UL 1449, Second Edition, UL 1283, cUL
ANSI/IEEE C62.41 – 1991, C62.45 – 1995
NEMA LS-1 – 1992
ELECTRICAL
Maximum Surge Current
The maximum surge current rating based on the 8/20ms test waveform is as follows. The rating is based on testing of a complete TVSS unit including fuses and all components that make up the TVSS system are expressed per mode. Third party NEMA LS-1 test results available on request.
Part Number L-L L-N N-G L-G
XXXXX 65kA 65kA 65kA 65kA
XXXXX 80kA 80kA 80kA 80kA
XXXXX 100kA 100kA 100kA 100kA
Maximum Continuous Operating Voltage (MCOV) 115% of nominal.
Minimum Repetitive Surge Current Capacity (Per ANSI/IEEE C62.41-1991 and ANSI/IEEE C62.45-1992)
The TVSS device is repetitive surge current capacity tested utilizing a 1.2x50ms, 20kV open circuit voltage, 8x20ms, 10kA short circuit Category C3 test waveform at one minute intervals.
The Blank device is capable of surviving 5,000 impulses without failure.
UL Witness Fault Current Rating: 65k AIC
Recommended Location Service Entrance Equipment, Distribution Equipment, Branch Panel
UL-1449, 2nd Edition Suppression Voltage Rating (SVR) & Clamping Voltages (all measured with 6” leads)
UL-1449 SVR6kV / 500A Cat. B3 Ringwave100kHz Cat. B3/C1Combination 6kV / 3kA Cat. C3Combination 20kV / 10kA
Part Number Voltage L-N N-G L-G L-N N-G L-G L-N N-G L-G L-N N-G L-G
XXX 120/240 400 400 400 600 650 600 700 700 700 800 850 800
XXX 120/208 400 400 400 600 650 600 700 700 700 800 850 800
XXX 277/480 800 1500 800 1000 1400 1100 1100 1650 1100 1200 1700 1200
Noise Attenuation
The TVSS device EMI-RFI noise rejection or attenuation value is measured in accordance with the procedures outlined in NEMA LS 1-1992/MIL 220A.
Noise Filter Capability 100KHz, 1MHz, 10MHz and 100MHz Max –44db attenuation.
Fusing One fuse per phase, a Surge Rated Fuse (Gould # VSP100) in combination with patented thermal fuse technology.
Standard Monitoring
The TVSS is monitored with a green indicating light per each phase
Contacts for remote monitoring (5 amp, 125VAC)
Connection 10 AWG Conductors
Environmental and External Conditions
Temperature -40? C to +60?C Operating Altitude 0 - 12,000 ft
Surface Temperature less than 55?C Humidity 95% RH, non-condensing atmosphere
No Audible Noise Frequency 50-60 Hz
