Mitsubishi Electric FR-A700 Technical Manual page 217

(2) Optimum excitation control mode
[Pr. 60 = 9]
F700 E700
Optimum excitation control is a control method which
controls excitation current to improve the motor
efficiency to maximum and determines output
voltage.
1) Control method
By converting the motor current to d-q axis to find
the excitation current Id and torque current Iq,
then obtain the motor loss by an original method.
Since application is fan and pump, low speed
torque is not required. Therefore, it controls
excitation current Id to make the motor loss
minimum focusing on the improvement of motor
efficiency rather than torque generation.
Namely, it controls the ratio of the excitation
current Id and torque current Iq becomes
maximum efficiency of the motor.
Torque current
I q
2) Restrictions
• Since it automatically sets the output voltage to
V/F control, the output voltage is not as set in [Pr.
0 Torque boost] and [Pr. 14 Load pattern selection].
• When the motor capacity is too small as
compared to the inverter capacity or two or more
motors are connected to one inverter, the energy
saving effect is not expected.
• Optimum excitation control functions only during
V/F control. Optimum excitation control is
disabled when Simple magnetic vector control,
Advanced magnetic vector control or General-
purpose magnetic vector control are selected.
3) Dedicated parameters
Dedicated parameters to automatically set the
output voltage are not available.
4) Energy-saving effect
• Motor efficiency improvement example (when
inverter operation frequency is 60Hz and the FR-
F740-3.7K and motor SF-JR 4P3.7kW are used)
100
Optimum excitation control
80
60
Energy-saving mode
V/F control
40
20
0 20 40
Motor load torque (%)
D700
Output torque
I d
Excitation current
60 80 100
• The motor efficiency has further improved by the
optimum excitation control and it is economical.
When the motor load torque is 10%
Control Method
Conventional V/F mode
Energy-saving mode
Optimum excitation control
The motor efficiency has increased approx. 15%
by the optimum excitation control as compared
to conventional V/F control.
• The energy-saving effect of the FR-F700 has
increased even during acceleration/deceleration
as compared to the FR-F500.
Conventional model(FR-F500)
100
6
12
90
FR-F700
0 10 20
Ratio of Motor Power Consumption during Acc./Dec.
(Driving of the Mitsubishi 400V
4 poles 45kW motors comparison)
• Ex. of blower operation characteristics (discharge
side)
(when the V/F pattern is constant torque load [Pr.
14 = 0])
Commercial
100
power
operation
80
60
40
20
0 10 20
• The optimum excitation control reduces the
motor loss to further save power consumption,
and it is economical.
When the inverter running frequency is 20Hz
• The optimum excitation control has reduced
approx.45% of the power consumption ratio as
compared to the V/F control method.
• Approx. 5% of the power consumption ratio has
been reduced as compared to the energy-saving
mode.
251
PARAMETER
Motor Efficiency
Approx. 65%
Approx. 75%
Approx. 80%
30 40 50
Motor Lord Torque (%)
V/F control
Energy
saving
mode
Optimum
excitation
control
30 40 50 60
Frequency (Hz)
2