Nidec Digistart D3 User Manual

Digistart D3: User Guide 49
Issue: G
7.2.1 Constant Current
Constant current is the traditional form of soft starting, which raises the current from zero to a specified level and
keeps the current stable at that level until the motor has accelerated.
Constant current starting is ideal for applications where the start current must be kept below a particular level.
Current
(%motor full load current)
700%
600%
500%
300%
100%
400%
200%
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
1
3
2
1: Initial Current (Pr 2C)
2: Current Limit (Pr 2B)
3: Full voltage current
Rotor speed (% full speed)
7.2.2 Current Ramp
Current ramp soft starting raises the current from a specified starting level (1) to a maximum limit (3), over an
extended period of time (2).
Current ramp starting can be useful for applications where:
• the load can vary between starts (for example a conveyor which may start loaded or unloaded). Set the
initial current (Pr 2C) to a level that will start the motor with a light load, and the current limit (Pr 2B) to a
level that will start the motor with a heavy load.
• the load breaks away easily, but starting time needs to be extended (for example a centrifugal pump where
pipeline pressure needs to build up slowly).
• the electricity supply is limited (for example a generator set), and a slower application of load will allow
greater time for the supply to respond.
Current
(%motor full load current)
700%
600%
500%
300%
100%
400%
200%
1
4
3
2
1: Initial Current (Pr 2C)
2: Start Ramp Time (Pr 2D)
3: Current Limit (Pr 2B)
4: Full voltage current
Time
7.2.3 Adaptive Control for Starting
In an adaptive control soft start, the Digistart D3 adjusts the current in order to start the motor within a specified time
and using a selected acceleration profile.
CAUTION
Adaptive Control cannot start the motor faster than a direct on-line (DOL) start. If the start ramp time (Pr
2D) is shorter than the motor's DOL start time, starting current may reach DOL levels.
Every application has a particular starting profile, based on characteristics of the load and the motor. Adaptive Control
offers three different starting profiles, to suit the requirements of different applications. Selecting a profile that
matches the inherent profile of the application can help smooth out acceleration across the full start time. Selecting a
dramatically different Adaptive Control profile can somewhat neutralise the inherent profile.
The Digistart D3 monitors the motor's performance during each start, to improve control for future soft starts.

Nidec Digistart D3 Specifications

General

Brand	Nidec
Model	Digistart D3
Category	Controller
Language	English