Page 270 - Motor_protection_and_control_Manual_motor_starters_ contactors

Star-delta starters protected by overload relays

With AF contactors - Open type version in kit form
Switching frequency diagrams

General
Switching frequency/hour, according to acceleration time and load factor. Respect of the following conditions enables utilization of the starter
without excessive overheating of the connections or nuisance tripping of the thermal overload relay.

Thermal overload relay
Intermittent periodic duty Example:
70
Switching frequency (ops/h) 50 ta = 8 s This corresponds to a 4 minute operating cycle (15 starts/hr) with 7 seconds
5 60 ta = 5 s Starting time of the motor: 7 second (use 8s curve) - Duty ratio: 63 % means
a permitted switching frequency of max. 15 operating cycles per hour.
40
acceleration, 2.5 minutes operation and 1.5 minutes rest.
30
ta = 12 s
20 ta = 10 s
ta = 15 s
ta = 20 s
10
0
0 10 20 30 40 50 60 70 80 90 100
Duty ratio (%)
ta: motor starting time

Electronic overload relay : please consult us

1SBC101958S0201

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