Hitachi SJ300 Series V/f, Free-setting, Torque Boost

3–15

SJ300 Inverter

c.After reaching the base frequency, the characteristic maintains a constant output voltage for higher frequencies.

Using parameter A045 you can modify the voltage gain of the inverter. This is specified as a percentage of the full-scale setting AVR (Automatic Voltage Regulation) in parameter A082. The gain can be set from 20% to 100%. It must be adjusted in accordance with the motor speci- fications.

Torque Boost – The Constant and

Variable Torque algorithms feature an

100%

A042 = 10

adjustable torque boost curve. When the

Torque boost

motor load has a lot of inertia or starting

friction, you may need to increase the

10%

low frequency starting torque character-

istics by boosting the voltage above the

normal V/f ratio (shown at right). The

frequency

boost is applied from zero to 1/2 the

base frequency. You set the breakpoint

6.0Hz 30.0Hz

f base =

of the boost (point A on the graph) by

60Hz

using parameters A042 and A043. The

A043 = 10%

manual boost is calculated as an

addition to the standard straight V/f line (constant torque curve).

Be aware that running the motor at a low speed for a long time can cause motor overheating. This is particularly true when manual torque boost is ON or if the motor relies on a built-in fan for cooling.

NOTE: Manual torque boost applies only to constant torque (A044=00) and variable torque (A044=01) V/f control.

NOTE: The motor stabilization parameter H006 is effective for constant torque (A044=00) and variable torque (A044=01) V/f control.

V/f Free-setting – The free-setting V/f inverter mode of operation uses voltage and frequency parameter pairs to define seven points on a V/f graph. This provides a way to define a multi- segment V/f curve that best suits your application.

Parameters	Drive Configuring

The frequency settings do require that F1 ≤ F2 ≤ F3 ≤ F4 ≤ F5 ≤ F6 ≤ F7; their values must have this ascending order relationship. However, the voltages V1 to V7 may either increase or decrease from one to the next. The example to the right shows the definition of a complex curve by following the setting require- ments.

Free-setting f7 (B112) becomes the maximum frequency of the inverter. Therefore, we recommend setting f7 first, since the initial value of all default frequencies f1–f7 is 0Hz.

Output voltage

Output

V2, V3

frequency

B101 to

B113

(odd)

(even)

B100 to B112

NOTE: The using of V/f free-setting operation specifies parameters that override (make invalid) certain other parameters. The parameters that become invalid are torque boost (A041/ A241), base frequency (A003/A203/A303), and maximum frequency (A004/A204/A304). In this case, we recommend leaving their settings at the factory default values.