20 • Starting Procedure
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8.2
Examples of starting curves
Light loads
- pumps, etc.
(In these cases actual current is always less than Current limit setting)
Current limit - set to 300-350%
Initial Voltage - set to 30%
Ramp-up time - set to 10 sec.
U%
100%
t
I%
600%
100%
50%
30%
10%
400%
350%
t
Upon start, the voltage quickly increases to the Initial Voltage value (30% of Un) and then gradually ramps-up to
nominal.
The current will simultaneously increase to peak current value (Lower than the current Limit setting), before
smoothly decreasing to the operating current.
High inertia loads – crushers, centrifuges, mixers etc.
(In these cases actual current is at Current limit setting in part of the starting time)
Current Limit - set to 400%
Initial Voltage - set to 40%
Ramp-Up time - set to 3 sec.
U%
100%
t
I%
600%
100%
40%
10%
400%
t
Upon start the voltage and current increase until current reaches Current Limit value. The voltage remains at
this value until motor reaches close to nominal speed, where current starts to decrease, voltage continues to
ramp-up to nominal.
End of process
Motor acceleration time
to full speed is as
required?
No
Yes
Apply Start command
If acceleration time is too short, increase
“Acceleration Time” setting and/or decrease C.L.
(when decreasing CL, make sure motor increases
speed gradually and does not stall).
A
