Functions
7.2 Start-up
SIRIUS 3RW55 soft starter
Manual, 08/2018, A5E35630887002A/RS-AB/002
85
Starting voltage The starting voltage determines the starting torque of the motor. A lower starting voltage
results in a lower switch-on torque and a lower starting current. Set the starting voltage to a
value that ensures that the motor starts up immediately and smoothly once the start
command reaches the 3RW55 soft starter.
• Factory setting: 30%
• Setting range: 20 ... 100%
• Increment: 5%
Ramp-up time The ramp-up time determines the time taken to increase the motor voltage from the
parameterized starting voltage to the line voltage. This has an influence on the motor's
acceleration torque which drives the load during the ramp-up operation. A longer ramp-up
time results in a shorter acceleration torque across the motor ramp-up time. The motor
therefore runs up more slowly and smoothly.
Set the length of the ramp-up time so that the motor can reach its rated speed by the time
the end of the ramp is reached. The actual motor starting time is load-dependent and can
differ from the parameterized ramp-up time. If you choose a time that is too short, the ramp-
up time ends before the motor has accelerated to speed. If the time selected is too short, a
very high starting current that equals the direct starting current at the same speed will occur.
In this case, the 3RW55 soft starter can switch itself off via the internal overload protection
function and go into fault mode.
If parameter value "0" is set, the motor is switched on with a ramp-up time of
approx. 100 ms.
• Factory setting: 10 s
• Setting range: 0 ... 360 s
• Increment: 0.1 s
Maximum starting time This time determines the period after which the drive must have completed its run-up. If the
drive is not operating under rated service conditions after the specified interval has expired,
the current limiting is interrupted and the motor is switched to 100%.
Maximum starting time ≥ ramp-up time.
• Factory setting: 0 s
• Setting range: 0 ... 1 000 s
• Increment: 0.1 s
See Breakaway pulse for startup functions (Page 94)
Breakaway voltage
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