APT TranSafe™ Circuitry
Various APT products include an ingenious circuit layout patented by US Patent 6,122,157.
Below is a diagram of our TranSafe™ Circuitry configuration on a per phase basis. The next page shows this circuit’s ‘Regenerative’ feature. Note that each mode has completely separated surge paths and safety elements. Thus, failure of any one mode limits failure to that mode.
Surge rated fusing is sized correctly. Overtemperature controls handle MOV faults below fusing thresholds. These are coordinated together to eliminate blind spots in real-world scenarios. All of these components are within the TVSS. No external or supplemental overcurrent protection is required to achieve UL Listed 200kA SCCRs.
This design allows several advantages:
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There are positive safety disconnectors for thermal and overcurrent protection
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This circuit has unique ‘regeneration’ qualities shown on the next page. For example, it can regenerate a new surge path under certain failure conditions. This is an important benefit in critical load applications.
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By monitoring at both ends of each N-G MOVs, the N-G MOVs are monitored, as are all L-N and L-G MOVs. This is an advantage for a couple of reasons:
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Every fuse and thermal disconnector is monitored
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Many TVSS do not monitor N-G MOVs
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Many TVSS do not monitor every MOV, rather selected MOVs.
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There is no chance of an inadvertent N-G MOV failure causing an accidental downstream N-G bond (i.e., due to shorted N-G MOV)
APT XGA, XT, XF and XP TVSS include this circuitry.
Stay in touch with APT Engineering Sales at 800-237-4567, visit our website, www.apttvss.com, or email us at
info@apttvss.com.
APT Engineering Sales
TranSafe™ Surge Path Regeneration – used in XGA, XT, XF and XP families
Recall that MOVs fail short. Any failed MOV will open the appropriate safety element and clear from the circuit. In a three-phase application, redundant surge paths are automatically generated due to the unique N-G configuration.
1.) Three Phase Configuration
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2.) Normal Operation
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3.) Simulate Random Failed MOV
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4.) Safety Element Clears Surge Component
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5.) Alternate Surge Path Generated
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Further examination reveals many contingency combinations. This system can operate when a neutral or ground conductor is corrupted. In unusual circumstances, it can also reconfigure itself so two MOV sets are series connected providing continued, albeit reduced protection. The advantages for Extreme-Duty applications are obvious.
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