Toshiba VF010H05 - Manual (Page 36)

JKSSS+ Series - 30
JKSSS+ Series 2.3 - 4.2KV
3.3.3 Current Limit
Factory Setting = 350% of unit FLA
Range = 200% - 500% of unit FLA
The current limit adjustment is factory set for 350% of the unit’s rating.
The range of adjustment is 200% to 500%. The main function of cur-
rent limit is to cap the peak current. It may also be used to extend the
ramping time if required. The interaction between the voltage ramp
and the current limit will allow the soft start to ramp the motor until the
maximum current is reached and the current limit will hold the current
at that level. The current limit must be set high enough to allow the
motor to reach full speed. The factory setting of 350% is a good start-
ing point. Do not set the current limit too low on variable starting
loads. This could cause the motor to stall and eventually cause
the overload protection to trip.
Note: If the motor does stall, refer to the motor manufacturer’s motor data
for the proper cooling time.
3.4 Deceleration Adjustments (Pump Control)
Decel extends the stopping time on loads that would otherwise stop too
quickly if allowed to coast to stop. Decel control provides smooth deceler-
ation until the load comes to a stop. Three adjustments optimize the deceleration
curve to meet the most demanding requirements. The unit is shipped from the
factory with the decel feature disabled.
Deceleration Applications
The unit is shipped from the factory with the decel feature disabled.
Apply power and adjust the soft start before enabling or modifying the
deceleration adjustments. Both acceleration and deceleration adjust-
ments should be made under normal load conditions.
The deceleration feature provides a slow decrease in the output voltage,
accomplishing a gentle decrease in motor torque during the stopping
mode. This is the OPPOSITE OF BRAKING in that it will take longer to
come to a stop than if the starter were just turned off. The primary use
of this function is to reduce the sudden changes in pressure that are
associated with “Water Hammer” and slamming of check valves with
centrifugal pumps. Decel control in pump applications is often referred to
as Pump Control.
In a pump system, liquid is being pushed uphill. The force exerted by
gravity on the column of liquid as it goes up hill is called the “Head
Pressure” in the system. The pump is sized to provide enough Output
Pressure to overcome the Head Pressure and move the fluid up the
pipe. When the pump is turned off, the Output Pressure rapidly drops
to zero and the Head Pressure takes over to send the fluid back down
the hill. A “Check Valve” is used somewhere in the system to prevent
this (if necessary) by only allowing the liquid to flow in one direction. The
kinetic energy in that moving fluid is suddenly trapped when the valve
slams closed. Since fluids can’t compress, that energy is transformed
into a “Shock Wave” that travels through the piping system looking for
an outlet in which it dissipates. The sound of that shock wave is referred
to as “Water Hammer”. The energy in that shock wave can be extremely
damaging to pipes, fittings, flanges, seals and mounting systems.
By using the Soft Stop/Deceleration feature of the soft starter, the pump
output torque is gradually and gently reduced, which slowly reduces the
pressure in the pipe. When the Output Pressure is just slightly lower than
the Head Pressure, the flow slowly reverses and closes the Check Valve.
By this time there is very little energy left in the moving fluid and the