145
7 - THEORY OF OPERATION
7.3.5 Open Loop Voltage Ramps and Times
General The open loop voltage ramp provides soft starting of a motor by increasing the voltage applied to motor from
the Initial Voltage setting to full (100%) line voltage. The ramp time sets the speed at which the voltage is
increased. Because this is an open loop control profile, the motor current during starting tends to be reduced;
however, the current is not limited to any particular level. This starting mode (old), is not commonly used
except in special circumstances. In most applications, the use of one of the other closed loop starting profiles
is recommended.
Initial Voltage This parameter sets the initial voltage level that is applied to the motor. To adjust the starting voltage level,
give the starter a run command and observe the motor operation. If the motor starts too quickly reduce the
initial voltage level. If the motor does not start rotating immediately or starts too slowly then increase the
initial voltage level until the motor just starts to rotate when a start command is given. If the initial voltage
level is set too low, a Fault 39 - No Current at Run may occur. In this case increase the initial voltage level to
permit more current to initially flow to the motor.
Ramp Time The ramp time setting is the time that it takes for the applied voltage to go from the initial voltage level to the
full voltage (100%) level. To make the motor accelerate faster, decrease the ramp time. To make the motor
accelerate slower, increase the ramp time.
Voltage
Time
Kick Time Ramp Time
Initial Voltage
Optional Kick
Current
Full Voltage
Start
command
Figure 32: Voltage Ramp
To Next Page
Loading...
Need help?
General
