Hitachi SJ300 Series Inverter Torque Control Algorithms, Algorithms, Torque Control

V/f control, constant torque

V/f control,

variable torque

V/f control, free-

setting curve

Sensorless vector

(SLV) control

3–14

“A” Group: Standard Functions

Torque ControlAlgorithms

Configuring Drive Parameters

The inverter generates the motor output according to the V/f algorithm or the sensorless vector control algorithm. Parameter A044 selects the inverter torque control algorithm for generating the frequency output, as shown in the diagram to the right (A244 and A344 for 2nd and 3rd motors, respectively). The factory default is 00 (constant torque V/f control).

Inverter Torque Control Algorithms

00 A044

01

Review the following descriptions to help you choose the best torque control algorithm for your application.

•The built-in V/f curves are oriented toward developing constant torque or variable torque characteristics (see graphs below).

02

Output

03

•	The free-setting curve provides an even	Sensorless vector,	04
		0Hz domain
	more flexible characteristic, but it
	requires more parameter settings.
•	Sensorless vector control calculates an	Vector control with	05
		sensor
	ideal torque vector based on current
	motor position, winding currents, and so
	on. It is a more robust control method than the V/f control methods. However, it is more
	dependent on actual motor parameters and will require you to set these values carefully or to
	perform the auto-tuning procedure (see “Auto-tuning of Motor Constants” on page 4–67) to
	obtain optimum performance.

•Sensorless vector control, 0Hz domain increases the low-speed torque performance (0– 2.5Hz) via an advanced Hitachi torque control algorithm. However, you will need to size the inverter for one frame size larger than the motor for proper operation.

•Vector control with sensor requires expansion card SJ–FB encoder feedback board and a motor shaft encoder. Choose this method when precise position/velocity control is required.

Constant and Variable Torque – The graph below (left) shows the constant torque characteristic from 0Hz to the base frequency A003. The voltage remains constant for output frequencies higher than the base frequency.

Output	Constant torque	Output	Variable torque
voltage		voltage
100%		100%

		a.	b.		c.
0	Maximum	0		Base	Maximum
Base		10% of
frequency	frequency	base		frequency	frequency
		frequency

The graph above (right) shows the general characteristic for variable torque. The curve may be best described in three sections, as follows:

a.The range from 0Hz to 10% of the base frequency is the constant torque characteristic. For example, a base frequency of 60Hz ends the constant torque characteristic segment at 6Hz.

b.The range from 10% of the base frequency to the base frequency is the variable (reduced) torque characteristic. The voltage is output in the curve of frequency to the 1.7 power.