Application To Motor - Mitsubishi Electric FR-F700PJ Series Manual

Application to Motor

Motor loss and temperature rise
The motor operated by the inverter has a limit on the continuous operating
torque since it is slightly higher in temperature rise than the one operated by
a commercial power supply. At a low speed, reduce the output torque of the
motor since the cooling effect decreases. When 100% torque is needed
continuously at low speed, consider using a constant-torque motor.
Torque characteristic
The motor operated by the inverter may be less in motor
torque (especially starting torque) than the one driven by the commercial
power supply. It is necessary to fully check the load torque characteristic of
the machine.
Motor torque
When the Mitsubishi standard squirrel-cage motor (SF-JR, 4-pole) and inverter of the same capacity are used, the torque characteristics are as shown
below.
Short time maximum torque
120
100
90
80
70
63
50
45
30
0
1 3 6
When the boost is increased
120
100
90
80
70
50
35
30
3 6
 The continuous operation torque is not an output torque of the motor. It is used to know the limit of permissible load torque for the use of
motor within the permissible temperature range. The maximum output torque of the motor is indicated as the maximum short-time torque.
 Depending on the capacity or number of poles of the motor, operation at 60Hz or higher may not be available. Fully check the maximum
permissible running frequency of the motor.
 The 60Hz torque reference indicates that the rated torque of the motor running at 60Hz is 100%, and the 50Hz torque reference indicates
that the rated torque of the motor running at 50Hz is 100%
 For 3.7K, the characteristic is shown with the stall prevention operation level adjusted.
 To operate continuously with the 50Hz torque reference, reduce the load torque to 85% or less.
 Under V/F control, the same torque characteristics apply to the SF-JR type with two, four, or six poles.
Since a constant-torque motor is greater in current than the standard motor, the inverter capacity may be one rank higher.
For a constant-torque motor, decrease the Pr.0 Torque boost setting.
Recommended value 0.75kW... 6%, 1.5 to 3.7kW... 4%, 5.5kW or higher...2%
When two or more motors are operated synchronously, torque imbalance is likely to occur as motor slip is smaller than that of the standard motor.
76
Application to standard motor
60Hz torque reference
220V
Continuous operation torque
(1.5K or lower)
Continuous operation torque (2.2K or higher)
20 30 60
Output frequency (Hz)
Maximum torque at the
initial value (boost setting)
Short time maximum
torque
Continuous operation
torque
20 30 60
Output frequency (Hz)
Application to constant-torque motor
Vibration
The machine-installed motor operated by the inverter may be slightly
greater in vibration than the one driven by the commercial power supply.
The possible causes of vibration are as follows.
1. Vibration due to imbalance of the rotator itself including the machine
2. Resonance due to the natural oscillation of the mechanical system.
Caution is required especially when the machine used at constant
speed is operated at variable speed. The frequency jump function
allows resonance points to be avoided during operation.
(During acceleration/deceleration, the frequency within the setting
range is passed through.) An effect is also produced if the PWM
carrier frequency in Pr. 72 is changed. When a two-pole motor is
operated at higher than 60Hz, caution should be taken since such
operation may cause abnormal vibration.
Short time maximum torque
104
200V
85
75
65
60
45
38
25
0
120 1 3 6
220V
When the boost is increased
200V
104
85
75
70
65
45
38
30
25
120 3 6
50Hz torque reference
Continuous operation torque
(1.5K or lower)
Continuous operation torque
(2.2K or higher)
20 30 50
Output frequency (Hz)
Maximum torque at the initial value (boost setting)
Short time
maximum torque
Continuous
operation torque
20 30 50
Output frequency (Hz)
120
120