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1.3 TYPICAL APPLICATIONS
Versatile features make the Protect 4A an ideal choice in a wide
range of motor applications. It should be considered for these
and other typical uses:
1) Basic protection on low and medium voltage motors. The
lowest horsepower selected for protection in an installa-
tion will depend on frequency of motor failure.
2)
Protection of motors and equipment from operator abuse
3) Personnel safety from shock hazard using sensitive ground
fault settings to detect winding shorts or leakage current
from moisture in mines.
4) Fault indication of ground fault without shutdown to warn
that corrective maintenance is required.
5) Mechanical protection of gears, pumps, fans, saw mills, cut-
ters and compressors against mechanical jam.
6) Simplified spare parts stocking using one universal model
to cover all motor sizes and settings.
7) Output of motor current suitable for programmable controller
interface (4–20mA).
The motor phase currents are sensed by 3 conventional 1 amp
or 5 amp secondary current transformers (CTs). If ground fault
sensing is required then a separate zero sequence ground fault
CT, through which all 3 phase conductors pass, is required. This
CT is available in 2 sizes: HGF-3 (3½" diameter window) or HGF-
5 (5½" diameter window).
Note: Ground fault sensing only works on systems that are solid
or resistance grounded. Ungrounded systems require an artifi-
cial ground, through the use of a zigzig transformer, for ground
fault sensing to work.
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