The following shows summary which facilitates the correct choice. Since general rules exist, will gladly give you further advice spe
cial cases such heavy starting.g.
Protection against: overload
• phase failure imbalance
• phase loss
E fficiency rotection device
current-dependent:
Fuses
O verload relays ith
p rotection device
in case phase failure
P rotection device,
tem perature-dependent:
Therm istor
m achine protection
CUSTORAPID-
Reasons for unwanted overloading
of the motor winding
1 Current overloading
2 Rated duty types S1-S8
to IEC 34-I
3 Operation when starting,
braking, reversing
4 Operation starting rates
OOperating cycles ops.
For direct starting, fuses around 1. The specifications relation short-circuit protection for contactors and overload relays
must noted when selecting the rating fuses circuit-breakers.
The effectiveness the available motor protection devices depends the range application. This would entail thermal overload the motor. They serve only short-circuit protection switchgear and cables.
S
2CDC 1GS 014 CG2G3
ABB STOTZ-KONTAKT GmbH
.Motor protection
Selection the protection device
Motor protection General aspects
Selection adequate motor protection great importance with regard the operational reliability and service life motor./h
D
D
D
D
5 Locked motor
In the case
of motors with
thermally critical rotor
6 Overload phase failure
7 Over-/undervoltage supply mains
D
D
8 Variation frequency supply mains D
9 Increased ambient temperature D
10 External heating
of the motor
(e.3 tim its rated current for a
sustained period.5 tim the rated current should used. order protect motors against short-circuits, advisable use fuses
aM conjunction with the thermal overload relay.: bearing heating)
D D
11 Obstruction otor cooling D
Efficiency protection device: not effective
■ partly effective
• fully effective
Note fuses
Fuses not protect motor against overload.5 2. fuse must withstand 1
