1 ZB12-…/XTOB…BC1 and ZB32-…/XTOB…CC1 overload relays
1.3 Description of device
32
ZB12-…, ZB32-…
11/16 MN03407004Z-DE/EN
www.eaton.com
Figure 4: Function of the phase failure sensitivity by means of tripping and differential bridge
a
Trip bridge
b
Differential bridge
c
Differential travel
s = Tripping distance
Figure 5: Wiring of the overload relay for the protection of AC or DC motors
(bimetallic release switched in series)
(
section 5.2, “Auslösekennlinien/Tripping characteristics”, page 49)
1.3.5 Re-closing
After tripping, the bimetallic releases must first cool down before the
overload relay can be reset. Manual and automatic reset can be selected by
means of a selector switch (
section 4.1.1, “Reset”, page 44).
In auto mode, the contacts automatically fall back after the bimetallic
releases have cooled down, whereas in manual mode the tripping must be
acknowledged locally on the overload relay.
Normal operation (no
fault)
three-phase overload
Failure of one phase
(two-phase load)
￫
When a ZB12-…/XTOB…BC1 or ZB32-…/XTOB…CC1 relay is to
be used for monitoring an AC or DC motor, the current must
flow across all three current paths in order to avoid early
tripping.
97
S
95
98 96
97 95
98 96
97 95
98 96
햲
햳
햴
DANGER
To ensure explosion-proof operation, the overload relay may
only be reset/switched on manually, or automatically via a
control interlock circuit for the motor or electrical machinery,
after the bimetallic release has cooled down.
Resets may be carried out at the installation or by trained
personnel in the control room.
