Hitachi AN070827-1 Control, Application, Phenomenon, Cause of the phenomenon, How to adjust

1.Inverter model SJ300

2.Control

Vector Control (V2 mode)

3. Application

General applications where operation at low speed or zero speed operation is required.

4. Phenomenon

Actual rotation of the motor does not match the target speed, or the rotation becomes unstable in the low frequency range (roughly less than 1 Hz). Or the motor shaft creeps even with a 0 Hz speed reference.

5. Cause of the phenomenon

V2 (closed-loop vector) control is a speed control method based on calculating shaft speed from the pulse train input from the motor encoder. In the case of low speed, the number of input pulses decrease and it becomes difficult to count them within the pulse counting period. Therefore on SJ300 V2 mode, in the absence of encoder pulses, the process of motor speed estimation (speed observing) is done by using information like motor current, motor parameters, etc. This process is an estimation, and will have some errors. It sometimes results in instability as described above in item 4.

Encoder pulse

Speed detection when there are pulses from the encoder

Speed observer

Speed data for speed control

Motor current Motor constants

6.How to adjust

(1)Adjust motor parameters, inertia parameter (J) in particular, and try to obtain optimal motor performance.

(2)Disable the speed-observing function by the following method:

c Set debug mode ON ([C091] = “01” and STR) using the standard keypad (cannot be changed via ProDrive)

d Configure a value of “4000” into [C193] and STR (default is “0000”) This change disables the speed observer function.

e Set debug mode OFF ([C091] = “00” and STR

(3)This phenomenon occurs at low speed. Therefore using an encoder having a higher PPR (pulse per revolution) will improve performance at lower speeds.

Hitachi America, Ltd.

© 2007 Hitachi America, Ltd.