Hitachi L2002 Torque Control Algorithms, Manual Torque Boost – The Constant

3–18

“A” Group: Standard Functions

Torque Control Algorithms

The inverter generates the motor output according to the V/f algorithm selected. Parameter A044 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 00 (constant torque).

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

Inverter Torque Control Algorithms

		A44
V/f control,	00
constant torque			Output
V/f control,	01
variable torque

Configuring Drive Parameters

The built-in V/f curves are oriented toward developing constant torque or variable torque characteristics (see graphs below). You can select either constant torque or reduced torque V/f control.

Constant and Variable (Reduced) 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. The graph below (right) shows the general variable (reduced) torque curve. The range from 0Hz to the base frequency is the variable characteristic.

V	A044 = 00	Constant torque	V	A044 = 01	Variable torque
100%			100%

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

Manual Torque Boost – The Constant								(%)
	V					A042 = 8
and Variable Torque algorithms feature an
	100%
adjustable torque boost curve. When the
					Torque boost
motor load has a lot of inertia or starting
friction, you may need to increase the low	8%			A
frequency starting torque characteristics
by boosting the voltage above the normal	3%
V/f ratio (shown at right). The function
	0										Hz
attempts to compensate for voltage drop in
			1.8Hz
the motor primary winding in the low									f base =
										60Hz
speed range. The boost is applied from							(%)
zero to 1/2 the base frequency. You set the		A043 = 3
breakpoint of the boost (point A on the

graph) by using parameters A042 and A043. The manual boost is calculated as an addition to the standard V/f curve.