Blocking Time And Blocking Current; Device Protection Model - Siemens 3RK1308‑0 00‑0CP0 Series Equipment Manual

6.7.4

Blocking time and blocking current

The blocking current specifies how much current is consumed by the motor (at rated voltage)
when the drive is blocked.
If the motor current exceeds 400 % of the set motor current I
ramps up, the blocking protection is tripped and a trip command is generated.
After the motor is switched on, the parameterized values for the blocking current and
blocking time apply. A switchover to the fixed values (400 %, 1 s) takes place depending on
the set motor protection class (CLASS 5/ 10 A → 5 s, CLASS 10, off → 10 s).
● The "Tripping due to motor blocking" and "Group fault" diagnostic messages are
generated
● The statistic "Number of motor overload trips" is incremented by 1
If the parameter "Group fault diagnostics" is set to "Enabled", a corresponding diagnostic
interrupt is set if blocking protection responds.
Setting ranges
The table below shows the possible setting range for the blocking current and the blocking
time:
Device parameters
Blocking current
Blocking time
6.7.5

Device protection model

To protect the switching elements in the main circuit against impermissible operating states,
an integrated intrinsic device protection is provided in the upper load range. The device
protection model consists of the relay protection model (dotted line) and the thermal motor
model (continuous line) with the highest permissible current setting. The device protection is
active 20 ms after the ON command. This means that, in the case of ET 200SP motor
starters, an overload trip may occur in the upper current range before the motor protection
trips. The device protection is active even when the overload protection is set to "Warn" and
the "Response of the thermal motor model on restart" parameter is set to "Delete".
Motor starter (3RK1308‑0**00‑0CP0)
Equipment Manual, 11/2019, A5E34821005002A/RS-AC/003
Default setting
800 % 150 ... 1500 % of I
Increment: 50 %
1 s 1 ... 7.5 s
Increment: 0.5 s
Functions
6.7 Substation monitoring
for a time > 1 s after the motor
e
Setting range
e
95