NIetz Electric Co.,Ltd
Soft starter SSN/SSA serie User Manual
13
6.
Control mode
This product has three start modes: Current Limit and Voltage Ramp and jogging. These start modes
is independent. Only one of them can be chosen. Text below introduce that the different of them
and which mode should be selected.
6.1 Voltage Ramp
The waveform of the voltage shows in Figure 6-1. U1 in figure is initial output voltage. When
starting, the output voltage is up to U1 immediately, and then ramps up gradually according to
the parameter Start Time “t” setting in advance. Then the motor accelerates continuously. When
the output voltage reaches the rate value Ue, the motor reaches the rate speed. Starting process
is finished. The Initial Voltage U1 and the Start Time t can be set according to the load. The
range of U1 is 5~75%Ue, and the range of t is 1~200s.
This mode is used in the state with large inertia load, or in the state in which the current is
not the important parameter but the stability is important. Using the mode, the mechanical stress
and starting striking may decreased greatly. The bigger the initial voltage is, the more the
initial torque and starting striking is. The time of starting is related to the parameter of
“starting time” and load. It is unconcerned with current limited. For detail see chapter 8 and
chapter 9.
6.2 Current Limit
At the Current Limiting mode, the output voltage increases quickly until the output current
reaches the limited current value Im. See figure 6-2. And then the output current maintains below
this limited value. Then the output voltage is increased gradually, and the motor accelerate
gradually; when the motor's speed is close to the rated，the output current decreases quickly
to the rated value Ie, the starting is over. The limited current value can be set according to
the load instance. The range of this parameter is 0.2-4Ie.
This mode is used in the state in which the current is very important parameter. Special in the
state in which the grid capacity is small. The parameter of the current limit multiples should
be set 2.5-3. If this value is small, the starting will be abnormal. At this mode, the time of
电压斜 坡起动
U e
U
U
1
t1 t 2 t 3
t
图 6-1
Voltage Ramp
Figure 6-1
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