Mitsubishi Electric 800 Series Instruction Manual page 145

 PM motor control
• Highly efficient motor control and highly accurate motor speed control can be performed by using the inverter with a PM
(permanent magnet embedded) motor, which is more efficient than an induction motor.
• The motor speed is calculated based on the output voltage and current from the inverter. It does not require a speed
detector such as an encoder. The inverter drives the PM motor with the least required current when a load is applied in
order to achieve the highest motor efficiency.
Inverter
Speed
command
Speed/magnetic
pole position
NOTE
• Perform offline auto tuning when using a PM motor.
• For the motor capacity, the rated motor current should be equal to or less than the inverter rated current. (It must be 0.4
kW or higher.) Using a motor with the rated current substantially lower than the inverter rated current will cause torque
ripples, etc. and degrade the speed and torque accuracies. As a reference, select the motor with the rated motor current
that is about 40% or higher of the inverter rated current.
• Single-motor operation (one motor to one inverter) is preformed.
• The overall wiring length with the motor is 100 m or less. (Refer to
144
5. PARAMETERS
5.2 Control method
PM sensorless vector control image
Output
voltage
Inverter
Controller
circuit
Magnetic field observer
∗1
Virtual motor
∗1 A magnetic field observer is a control
Output
method that calculates the motor
current
speed/magnetic pole position based
on the motor voltage and current of a
virtual motor which is set up in the
inverter.
page 48.)