Start-up 01.04
7-18 SIEMENS AG 6SG7000-0BA76
SIMOTRAS HD Operating Instructions
t
t
t
t
U638 (- U639)*
)
(S4)
U636 (- U637)*
)
(S3)
U634 (- U635)*
)
(S2)
S2
n
S3
S4
Actual speed
value
(K0167)
Control
output S2
(B0528)
Control
output S3
(B0530)
Control
output S4
(B0532)
U638 (S4)
U636 (S3)
U634 (S2)
*
)
Hysteresis
Fig. 7.6.15.2 Time characteristic of rotor contactor stepping
Preventing current peaks during rotor stage stepping:
• To prevent excessive stator current values occurring when switching in the next rotor contactor,
it is desirable, at the same time as the contactor is switched in, to reduce the I component of the
speed controller by roughly the same proportion by which the rotor resistance is also reduced.
This enables the rotor current to be held at about the same value as before the switchover,
despite the fact that the rotor resistance will now be lower.
Setting instructions:
U641 Reduction when connecting stage 1: R (stage 1) / R (counter-torque stage)
U642 Reduction when connecting stage 2: R (stage 2) / R (stage 1)
U643 Reduction when connecting stage 3: R (stage 3) / R (stage 2)
U644 Reduction when connecting stage 4: R (stage 4) / R (stage 3)
Example: Quotient = 0.8
=
∧
U641 = 80.0%
Increasing rotor contactor service life:
Off-load switching is recommended to increase the service life of the rotor contactors.
• U640.001: Pick-up time of rotor contactors (zero current interval)
• U640.002: Drop-out time of rotor contactors (zero current interval)
A disadvantage of off-load switching of rotor contactors:
there is a torque-free interval, and this may lead to a deviation in the speed.
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