BENSHAW RediStart MX3 Series, User Manual

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NOTE : Depending on loading, the motor may achieve full speed at any time during the Power ramp. This
means that the Maximum Power level may not be reached. Therefore, the maximum power level is the
maximum power level that is permitted. However, the motor power may not necessarily reach this value
during all starts.
Ramp Time
When in Power acceleration mode, the ramp time setting is the time it takes for the power to go from the
initial power setting to the maximum power setting. To make the motor accelerate faster, decrease the ramp
time. To make the motor accelerate slower, increase the ramp time.
If the ramp time expires before the motor reaches full speed, the starter maintains the Maximum Power level
until either the motor reaches full speed, the UTS timer expires, or the motor thermal overload protection trips.
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NOTE: Setting the ramp time to a specific value does not necessarily mean that the motor takes that exact
amount of time to accelerate to full speed. The motor and load may achieve full speed before the ramp time
expires if the load does not require the set ramp time or set power level to reach full speed. Alternately, the
motor and load may take longer than the set ramp time to achieve full speed depending on the parameter
settings and load level.
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.
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7 - THEORY OF OPERATION
Voltage
Time
Kick Time Ramp Time
Initial Voltage
Optional Kick
Current
Full Voltage
Start
command
Figure 42: Voltage Ramp