Toshiba JKSSS Series Instruction Manual page 61

Basic Installation and Operation
Guide
This feature can be used with or without the Maximum Current Limit setting. To achieve Current Ramping select
CURRENT for START RAMP #1 TYPE setpoint and set the MAXIMUM CURRENT #1 setpoint to the desired level.
• Current Limit Only (Current Step) uses the Current Limit feature exclusively. This method of starting eliminates
the soft start voltage/current ramp and instead, maximizes the effective application of motor torque within the
limits of the motor. In this mode, setpoint RAMP TIME #1 is set to minimum so that the output current jumps to the
current limit setting immediately. Typically used with a limited power supply when starting a difficult load such as a
centrifuge or a deep well pump, when the motor capacity is barely adequate (stall condition or overloading occurs)
or if other starting modes fail. Since ramp times are set to minimum, START RAMP #1 TYPE is set to either
VOLTAGE or CURRENT.
• Initial Torque (Initial Voltage #1 or Initial Current #1) sets the initial start point of either Voltage Ramp or the
Current Ramp. Every load requires some amount of torque to start from a standstill. It is inefficient to begin
ramping the motor from zero every time, since between zero and the WK2 break-away torque level, no work is
being performed. The initial torque level should be set to provide enough torque to start rotating the motor shaft,
enabling a soft start and preventing torque shock damage. Setting this start point too high will not damage the
starter, but may reduce or eliminate the soft start effect.
• Ramp Time #1 sets the maximum allowable time for ramping the initial voltage, current (torque) or power setting
to either of the following:
- The Current Limit setting when the motor is still accelerating.
- Full output voltage if the Current Limit is set to maximum.
- KW if Power Ramp is selected.
Increasing the ramp time softens the start process by gradually increasing the voltage, current or power. Ideally,
the ramp time should be set for the longest amount of time the application will allow (without stalling the motor).
Some applications require a short ramp time due to the mechanics of the system. (i.e., centrifugal pumps, because
pump problems can occur due to insufficient torque).
• Current Limit sets the maximum motor current the starter will allow during the acceleration. As the motor begins
to ramp, the Current Limit feature sets a maximum at which the current draw is held. Current Limit remains in
effect until the following occurs:
1) The motor reaches full speed (Detected by the At-Speed detection circuit) or;
2) The Overload Protection trips on Motor Thermal Overload. Once the motor reaches full speed, the Current
Limit feature becomes inactive.
In the Voltage Ramp Profile, the voltage output is increased until it reaches the Current Limit. Ramp time is the
maximum amount of time it takes for the voltage to increase until the Current Limit setting takes over. With some
load conditions, the Current Limit is reached before the Ramp Time expires. The Current Ramp profile varies the
output voltage to provide a linear increase in current up to the Maximum Current setpoint value. A closed loop
feedback of motor current maintains the Current Ramp profile.
SP2.4 Start Ramp 2 Type: Please refer to Ramp 1 settings for Ramp 2 Type: Voltage selection.
Start Ramp 2: Power
• The Power Ramp feature has three programmable setpoints, Initial Power, Ramp Time and Maximum Power.
- The Initial Power setpoint allows the user to define an initial KW (motor power) value that will be applied to the
motor when the start sequence is begun. It has a range of 0-100% and a default value of 20%.
- The Ramp Time functions as all other ramp time and allows the user to define a time period during which the
applied KW (motor power) will be increased linearly to the Maximum Power value setpoint. The adjustment range
is 1-120 seconds. Once the Power Limit value is reached, the system enters a constant power
mode that regulates the applied motor power until the motor reaches full speed.
- The Maximum Power setpoint has an adjustment range of 0-300% and a default value of 80%.
TOSHIBA
CAUTION
!
Do not use on an unloaded un-coupled motor!
The power ramp should only be used with a loaded
motor.
JKSSS Series Solid State Soft Starters
Cont.
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