Hitachi L2002 Velocity Profiles

Velocity Profile

1–22

Introduction to Variable-Frequency Drives

Velocity Profiles

Getting Started

The L2002 inverter is capable of sophisticated speed control. A graphical representation of that capability will help you understand and configure the associated parameters. This manual makes use of the velocity profile graph used in industry (shown at right). In the example, acceleration is a ramp to a set speed, and deceleration is a decline to a stop.

Speed Set speed

Accel Decel

0

t

Acceleration and deceleration settings specify	Speed	Maximum speed
the time required to go from a stop to
maximum frequency (or visa versa). The
resulting slope (speed change divided by time)
is the acceleration or deceleration. An increase
in output frequency uses the acceleration	0
slope, while a decrease uses the deceleration
			Acceleration	t
slope. The accel or decel time a particular
			(time setting)
speed change depends on the starting and

ending frequencies. However, 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 L2002 inverter can store up to 16 preset	Speed
speeds. And, it can apply separate acceleration			Speed 2
and deceleration transitions from any preset to
		Speed 1
any other preset speed. A multi-speed profile
(shown at right) uses two or more preset	0
speeds, which you can select via intelligent
				t
input terminals. This external control can		Multi-speed Profile

apply any preset speed at any time. Alterna-

tively, 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 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 FWD and REV commands determine the direction before the motion starts.

Speed Forward move

0

t

Reverse move

Bi-directional Profile

NOTE: The L2002 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.