Application To Standard Motors; Motor Loss And Temperature Rise; Torque Characteristic; Motor Torque - Mitsubishi Electric FR-A700 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.
Maximum torque for short time
Maximum torque for short time (0.4 to 3.7K)
200
* (5.5K to 55K)
150
100
70
(%)
63
0
0.3
*4
150
140
110
100
80
70
63
(%)
30
10
0
1 3 6
⋅
200% torque (60Hz torque reference) is output at 0.3Hz operation under real
sensorless vector control. (0.4 to 3.7K)
(* 0.3Hz 150% torque for the 5.5K to 55K)
⋅
A 60Hz torque reference indicates that the rated torque of the motor running at
60Hz is 100%, and a 50Hz torque reference indicates that the rated torque of
the motor running at 50Hz is 100%
Continuous torque (real sensorless vector control)
60Hz Torque Reference
0.4K to 3.7K 5.5K
100
95
90
85
80
70
65
37K to 55K 37K to 55K 37K to 55K
50
45
V/F control V/F control V/F control
(%)
(0.2K to 55K) (0.2K to 55K) (0.2K to 55K)
30
0
3 6 20 30 40
A general-purpose, squirrel-cage motor must be used at lower continuous operating torque in rated operation as shown in the chart since the
cooling capability of the fan installed on the rotor reduces at a lower speed. (Instantaneous torque occurs)
200/220V 60Hz or 200V 50Hz in the chart indicates a motor torque reference (base frequency set in Pr.3 of the inverter) and is not the frequency of the power
supply. You can also set 60Hz in a 50Hz power supply area.
As shown in the chart, the 60Hz torque reference setting allows you to use the motor more efficiently as it can bring out the 100% torque of the motor
continuously.
93

Application to standard motors

60Hz Torque Reference
220V
20 60
Output frequency (Hz)
*3
*2 *1
220V
20 60
Output frequency (Hz)
7.5K to 30K
220V
200V
60 120
Output frequency (Hz)
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 Pr.72 PWM frequency
selection is changed. When a two-pole motor is operated at higher
than 60Hz, caution should be taken since such operation may cause
abnormal vibration.
Maximum torque for short time(0.4 to 3.7K)
170
200V
130
100
53
(%)
0
120
0.3
130
200V
120
95
80
67
53
(%)
25
9
120 1 3 6
*1. Torque boost minimum (0%)
*2. Torque boost standard (initial value)
*3. Torque boost large (0.4K, 0.75K... 10%, 1.5K to 3.7K... 7%, 5.5K, 7.5K... 6%,
11K or more... 4%)
*4. Torque boost adjustment (3.7kW or less)
0.4 to 3.7K
85
80
75
70
65
60
55
45
38
(%)
25
0
3 6
50Hz Torque Reference
* (5.5K to 55K)
20 50
Output frequency (Hz)
*4 *3
*2 *1
20 50
Output frequency (Hz)
50Hz Torque Reference
5.5K 7.5K to 30K
37K to 55K 37K to 55K 37K to 55K
V/F control V/F control V/F control
(0.2K to 55K) (0.2K to 55K) (0.2K to 55K)
20 30 40 50 120
Output frequency (Hz)
120
120