Driving With Sensorless Vector Control - Hitachi WJ Series User Manual

Chapter 9
9.5.7

Driving with Sensorless Vector Control

 How to use the inverter for applications that require a high torque at startup, such as
Q
conveyance and crane driving?
 What should be done when motor rotation slows relative to the frequency command for heavy
loads?
 How to use sensorless vector control to achieve stable operation with a high startup torque and
high level of precision?
 Sensorless vector control uses the inverter output voltage and current, and the set motor
A
constant to infer and control motor speed and output torque. This high precision mode of
operation allows for a high startup torque starting from the low frequency range (0.5 Hz) while
alleviating changes in motor speed even when load changes are made.
 When using sensorless vector control, be sure to set the specifications and motor constants for
the motor to be used. For details, refer to "8.1.3 Setting the Motor Specification Label Data to
Parameters", "8.1.5 Setting Motor Constant", or "8.3 Carrying Out Motor Auto-tuning".
 When changes in the load occur, you can adjust the following capability to change the actual
rotation speed according to the frequency command by using " Async. Motor speed response
*1
[H005] ". Hunting may occur in the motor if the speed response is too large. Make the proper
adjustments referring to the details provided on the next page.
 Sensorless vector control cannot be selected in low duty rating (LD mode).
 Inverter characteristics may be insufficient for long wiring lengths (20 meters or more), or when
!
controlling motors from other manufacturers.
 Sufficient inverter characteristics may not be obtainable when motors that are two frame sizes
smaller than the maximum applicable motor are operated.
 At low speeds (several Hz or less), the direction of rotation may be reversed relative to the RUN
command direction. In such cases, enable the "Direction reversal protection selection [b046]".
For details, refer to "9.4.3 Limiting the Rotation Output Direction".
 To secure torque during operation in the low speed range, even if the "Carrier frequency [b083]"
is set to a value exceeding 2 kHz, it is automatically lowered to 2 kHz. In addition, since the
carrier frequency increases with acceleration, so the electromagnetic sound and other
phenomena from the motor may vary depending on the output frequency.
 If "AVR function selection [A081]
current may increase and normal operation may be hindered when the voltage received from
the inverter exceeds the rated voltage of the drive motor. If this occurs, set this to "Always
enable (00)".
 When using a motor with frame size smaller than that of the inverter capacity, set a value that
does not exceed the value in the following formula for "Torque Limit [b041] to [b044]", and
enable the torque limit to prevent motor burnout. For details on the torque limit function, refer
to "9.6.2 Driving with Limited Torque".
[Torque limit setting] = 200% x [Motor rated current] / [Inverter rated output current]
(Example) 0.75 kW inverter (rated output current = 5.0 A) +0.4 kW motor (rated current = 2.3 A):
[Torque limit setting] = 200% × (2.3 A / 5.0 A) = 92 %
*1. "2nd-motor control [SET]" target parameter. The second control parameter is also subject to setting.
*1
" is set to "Disable (01)" or "Disable at deceleration (02)", the
9-5-11
Inverter Functions