Hitachi X200 Series instruction manual Torque Control Algorithms, Manual Torque Boost The Constant

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Torque Control Algorithms

Inverter 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).

Variable freq. control, 00 constant torque

Variable freq. control, 01 reduced torque

Variable freq. control, 06 reduced torque1

A044

Output

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

The built-in V/f curve 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.

Configuring Drive Parameters

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

VA044 = 01 Variable torque

100%

V	A044 = 00	Constant torque
100%
0			Hz
	Base		Max.
	freq.		freq.
V	A044 = 06	Variable torque
100%

0	Hz	0		Hz
	Max.		Base	Max.
Base		10% Base
freq.	freq.	freq.	freq.	freq.

The graph above (right) shows the variable (reduced) torque curve, having constant torque from 0Hz to 10% of the base frequency. This helps to achieve higher torque at low speed even with reduced torque curve.

Manual Torque Boost – The Constant					V
and Variable		Torque	algorithms	A042 = 5(%)
feature an adjustable torque boost				100%
curve. When the motor load has a lot of
inertia or starting friction, you may				5% boot of		A
need to increase the low frequency				the base
starting	torque	characteristics by		frequency					Hz
boosting the voltage above the normal				0
						1.8Hz	30Hz	fbase = 60Hz
V/f ratio (shown at right). The function
attempts	to compensate		for voltage
						A043 = 3(%)
drop in the motor primary winding in

the low speed range.

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