Toshiba 18 - 1250 A Benutzerhandbuch

67 

3. Closed Loop Current (Torque) Ramping is good for smooth linear 
acceleration of output torque. Ramp Time becomes the time from Initial 
Torque and Current Limit settings. Output torque is constantly updated 
using an internal PID feedback loop to provide a linear ramp, and 
therefore the available torque is maximized at any given speed. The 
best use of this feature is for applications where rapid changes in torque 
may result in load damage or equipment changes. Examples would be: 
ƒ  Long overland conveyors where belt stretching may occur. 
ƒ  Low pressure pumps where slight surges at the end-of-ramp may 

pose mechanical problems. 

ƒ  Fans and mixers where blade warping is a problem. 
ƒ  Material handling systems where stacked products may fall over or 

break. 

This feature can be used with or without the Maximum Current Limit 
setting. 

To achieve Torque Ramping with the TE Series, set the Ramp Profile 
(F010) to 0002 or 0004 (Current Ramp), and the Maximum Current Limit 
setting (F014) to the desired level. Initial Torque setting comes from the 
Initial Current function F012. 

 

4. Current Limit Only (Current Step) starting means using the Current 
Limit feature exclusively without the benefit of soft starting by ramping 
the voltage or current first (also known as Pedestal Starting). This will 
maximize the effective application of motor torque within the limits of the 
motor. In this mode, Initial Torque is set to maximum and Ramp Time is 
set to minimum, so the output current jumps to the Current Limit setting 
immediately. Examples of when to use this mode are: 
ƒ  Applications with a severely limited power supply 
ƒ  When starting a difficult load such as a centrifuge or deep well 

pump 

ƒ  When the motor capacity is barely adequate without stalling or 

overloading. 

ƒ  It is a good choice when other starting modes fail. 
Since ramp times are set to minimum, this mode functions in either 
Voltage Ramp or Current Ramp setting. 

 

 

Ramp Parameter Descriptions 
Following are detailed descriptions of the individual settings that make 
up each ramp profile. 

Initial Torque (Initial Voltage or Initial Current).  
These functions set the initial start point of either the Voltage Ramp or 
Current Ramp as programmed in F010. Every load requires at least 
some amount of torque to start from a standstill. It is not efficient to 
begin ramping the motor from zero every time, since between zero and 
the (WK

2

) breakaway torque level, no useful work is being performed. 

The initial torque level should be set to provide just enough torque to 
make the motor shaft begin to rotate, enabling the softest possible start 
and preventing torque shock damage to the mechanical components. 
Setting this function too high will not damage the starter, but may 
reduce or eliminate the soft start advantages.