ABB CIRCUIT SHIELD 49/50 Instructions Manual - Page 5
Browse online or download pdf Instructions Manual for Relays ABB CIRCUIT SHIELD 49/50. ABB CIRCUIT SHIELD 49/50 14 pages. Overcurrent relay for motor protection
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Motor Overcurrent Relay
Solutions to the equation yielding values greater than 1 are not valid, and should be set equal to 1.
IB 7.2.1.7-4
Page 5
Note that the solution is in terms of the time required for a trip. There is no requirement that the second overload be the
same magnitude as the first. For example if the second overload is 2X pickup, and T2 was calculated as 100%, then the
second overload can last as long as 60 sec. (using time dial #1), before a trip occurs. However, if the second overload
happens to be 4X pickup, it can only last 16 seconds or a trip will occur. The minimum interval between overloads may be
calculated by setting T2= 1 ; then T12 = T1 TR. Another example is shown graphically in Fig. 5 for a repetitive overload of
200% tap value, with the 49 unit time dial set at 2 minutes.
LOCKED ROTOR PROTECTION (Function 51)
This element is designed to provide stalled rotor and high-overload protection. The shape of this curve accommodates both
full and reduced voltage starts. The time delay is adjustable from 5 to 30 seconds at 6 times the overload setting, allowing its
use even with motors having very long starting times.
PHASE FAULT PROTECTION (Function 50)
This instantaneous element is adjustable from 4 to 16 multiples of the overload unit setting. The operating time of this unit
is such that on fused motor starters the relay will trip before the fuse opens on low grade faults, thus saving fuses, but the fuse
will be faster than the relay for faults above the interrupting capability of the starter.
COMPOSITE CHARACTERISTIC
An example of the composite Time-Current Tripping Characteristic for a relay equipped with the 49, 50, and 51 elements is
given in Figure 6. For this example the relay settings are: pickup tap at 120% of motor full load current; time dial (49) set
at 2 minutes; time dial for stall unit at 5 seconds; and instantaneous pickup at 7.2 times full load amperes.
Relay Type
49
49/50
49/50/51
CHARACTERISTICS OF COMMON UNITS
Function
Overload
Overload,
Fault
Overload,
Fault,
Locked Rotor
Connection
Diagram
16D414B
16D414B
16D414B
Control
Voltage
24 Vdc
48 Vdc
110 Vdc
125 Vdc
220 Vdc
250 Vdc
120 Vac
24 Vdc
48 Vdc
110 Vdc
125 Vdc
220 Vdc
250 Vdc
120 Vac
24 Vdc
48 Vdc
110 Vdc
125 Vdc
220 Vdc
250 Vdc
120 Vac
Catalog
Number
414A0096
414A0036
414A0006
414A0046
414A0026
414A0056
414A0066
414B0096
414B0036
414B0006
414B0046
414B0026
414B0056
414B0066
414C0096
414C0036
414C0006
414C0046
414C0026
414C0056
414C0066