Page 401 - Contactors_Catalogue

ABB MOTOR CONTROL AND PROTECTION FOR ROLLING STOCK APPLICATIONS 8/17

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DOL and reversing starters protected by overload relays
With AF..B contactors - Open type version in kit form
Switching frequency diagrams

General
Overload relays cannot be operated at any arbitrary switching frequency in order to avoid tripping. Applications involving up to
15 operations per hour are acceptable. Higher switching frequencies are permitted if the duty ratio and the motor starting time are
allowed for and if the motor's making current does not appreciably exceed 6 times the rated operating current. Please refer to the
adjacent diagram for guideline values for the permitted switching frequency.

Thermal overload relay
Intermittent periodic duty Example:

(Op/h)
Switching frequency (ops/h) switching frequency 120 t = 1.5 s a Starting time of the motor: 1 second - Duty ratio: 40 % means a permitted
140
switching frequency of max. 60 operating cycles per hour.
100
80
t = 0.5 s
a
60
a
t = 1 s
40
a
20
a
t = 5 s
0 t = 3 s
0 20 40 60 80 100 (%)
duty ratio
Duty ratio (%)
ta: motor starting time

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1SBC100259S0201