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Introduction to Variable-Frequency Drives

Geting Started

Acceleration and deceleration settings

 

specify the time required to go from a stop to

 

maximum frequency (or visa versa). The

Speed

resulting slope (speed change divided by

 

time) is the acceleration or deceleration. An

 

increase in output frequency uses the accel-

 

eration slope, while a decrease uses the

 

deceleration slope. The accel or decel time a

 

particular speed change depends on the

 

starting and ending frequencies. However,

0

the slope is constant, corresponding to the

 

full-scale accel or decel time setting.

 

For example, the full-scale acceleration

 

setting (time) may be 10 seconds—the time

 

required to go from 0 to 60 Hz.

 

The SJ300 inverter can store up to 16 preset

 

speeds. And, it can apply separate accelera-

Speed

tion and deceleration transitions from any

preset to any other preset speed. A multi-

 

speed profile (shown at right) uses two or

 

more preset speeds, which you can select via

 

intelligent input terminals. This external

 

control can apply any preset speed at any

 

time. Alternatively, the selected speed is

 

infinitely variable across the speed range.

 

You can use the potentiometer control on the

 

keypad for manual control. The drive

 

accepts analog 0-10V signals and 4-20 mA

 

control signals as well.

 

The inverter can drive the motor in either

 

direction. Separate FW and RV commands

 

select the direction of rotation. The motion

Speed

profile example shows a forward motion

 

followed by a reverse motion of shorter

 

duration. The speed presets and analog

 

signals control the magnitude of the speed,

 

while the FW and RV commands determine

 

the direction before the motion starts.

 

Maximum speed

Accelerationt

Acceleration (time) setting

Speed 2

Speed 1

t

Multi-speed Profile

Forward move

t

Reverse move

Bi-directional Profile

NOTE: The SJ300 can move loads in both directions. However, it is not designed for use in servo-type applications that use a bipolar velocity signal that determines direction.