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Technical Data
Effective: May 1998
Page
6
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.
For the Instantaneous curve see 70C1007.
4. The Long Delay Pickup Point (indicated by rapid flashing of unit status LED on the product) nominal
occurs at 110% of the lr current, with a
±
5% tolerance. The short delay settings have conventional 100%,
±
5% as the pickup points.
5. With zone interlocking on Short Delay utilized and no restraining signal, the minimum time band
applies regardless of the setting.
6. This curve is shown as a multiple of the Long Delay Setting.
7. For additional curve tolerances contact Cutler-Hammer.
8. Total clearing times shown include the response times of the trip unit, the breaker opening and the
extinction of the current.
9. M1 setting
200A through 1250A rating.
M1 = 14 x lr
1600A through 2500A rating.
M1 = 12 x lr
3000A through 3200A rating.
M1 = 10 x lr
10. See Instantaneous Curve 70C1007, note 9.
Ratings
Table R10 – Magnum DS Circuit Breakers with Digitrip RMS 520 Trip Unit
Typical Long Delay and Short Delay Time/Phase Current Characteristic Curve (LS)
Magnum DS
Metal-Enclosed
Low-Voltage Switchgear
Curve No. 70C1006
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