Technical Data
Effective: May 1998
Page
7
TD.44A.01.T.E
Cutler-Hammer
1. There is a memory effect that can act to shorten the Long Delay. The memory effect
comes into play if a current above the long delay pickup value exists for a time and
then is cleared by the tripping of a downstream device or the circuit breaker itself.
A subsequent overload will cause the circuit breaker to trip in shorter time than
normal. The amount of time delay reduction is inverse to the amount of time that
has elapsed since the previous overload. Approximately five minutes is required
between overloads to completely reset memory.
2. The end of the curve is determined by the interrupting rating of the circuit breaker.
3. For ground fault time/current curve see 70C1008.
4. This curve is shown as a multiple of the Rating Plug (ln).
5. The instantaneous settings have conventional 100%,
±
10% as the pickup points.
6. For additional curve tolerances contact Cutler-Hammer.
7. Total clearing times shown include the response times of the trip unit, the breaker
opening and the extinction of the current.
8. Additional settings of "OFF" and M1 are also available with
200A through 1250A rating.
M1 = 14 x ln
1600A through 2500A rating. M1 = 12 x ln
3000A through 3200A rating. M1 = 10 x ln
9. For breakers rated 3200A and less having a 100 kA rms interruption rating, an additional
high Instantaneous Trip Module is provided in the breaker set to pick up a 170 kA
±
10%
instantaneous peak current level. This protection is functional even when the
Instantaneous is set to "OFF" position.
Magnum DS
Metal-Enclosed
Low-Voltage Switchgear
Ratings
Table R11 – Magnum DS Circuit Breakers with Digitrip RMS 520 Trip Unit
Typical Instantaneous Time/Phase Current Characteristic Curve (I)
Curve No. 70C1007
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