Hitachi SJ100 Torque Control Algorithms, Torque Boost –

3–13

SJ100 Inverter

Torque Control Algorithms

The inverter generates the motor output according to the V/f algorithm or the sensor- less vector control algorithm. Parameter A_44 selects the inverter algorithm for generating the frequency output, as shown in the diagram to the right (A244 for 2nd motor). The factory default is 02 (sensorless vector control).

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

Inverter Torque Control Algorithms

	00	A 44
V/f control,
constant torque	01		Output
V/f control,
variable torque
Sensorless vector	02
(SLV) control

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

•Sensorless vector control calculates an 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 perform the auto-tuning procedure (see “Auto-tuning for Sensorless Vector Control” on page 4–35).

Constant and Variable (Reduced) Torque – The graph below (left) shows the constant torque characteristic from 0Hz to the base frequency A_03. The voltage remains constant for output frequencies higher than the base frequency. The graph below (right) shows the general variable (reduced) torque curve. The range from 0Hz to the base frequency is the variable characteristic.

V	A_44 = 00	Constant torque	V	A_44 = 01	Variable torque
100%			100%

0			Hz	0			Hz
	Base
		Max.			Base	Max.
	freq.	freq.			freq.	freq.

Parameters Drive Configuring

Torque Boost – The Constant and Variable Torque algorithms feature an adjustable torque boost curve. When the motor load has a lot of inertia or starting friction, you may need to increase the low frequency starting torque characteristics by boosting the voltage above the normal V/f ratio (shown at right). The boost is applied from zero to 1/2 the base frequency. You set the breakpoint of the boost (point A on the graph) by using

V			A_42 = 11
100%
		Torque boost
11.8%	A

0				Hz
	6.0Hz 30.0Hz
			f base =
		(%)	60Hz
A_43 = 10