4. CHARACTERISTICS Where, •
NR : Rated motor speed (r/rain)
1
4.1 OVERLOAD CHARACTERISTICS JM (=GD_/4) : Motor moment of inertia
(kg.rr_X10-' =lb'in's 2 ×10 -3)
The overload protective circuit built in SERVOPACK JL (=GD[/4) : Load moment of inertia
prevents the motor and SERVOPACK from overloading (kg" n{ × 10- 4 = lb-in" s 2 x 10- 3)
and restricts the allowable conduction time of Kt : Torque constant of motor (N'm/A=lb'in/A)
SERVOPACK. (See Fig. 4.1.) IR : Motor rated current (A)
a =I_/IR : Acceleration/deceleration current
The overload detection level is set precisely by the constant
hot start conditions at an ambient temperature of Is : Acceleration/deceleration current
55°C and cannot be changed. (Acceleration/deceleration current a times
the motor rated current) (A)
NOTE fl =IL/IR : Load current constant
Hot start is the overload characteristics when the IL : Current equivalent to load torque
(Load current fl times the motor rated
SERVOPACK is running at the rated load and current) (A)
thermal ly saturated. I_%_,,:_1 l
MOTOR _NN N_:
ARMATURE t' I f _TIME
CURRENT I _ - [_| _,
, I_ T_
' I
MOTOR_
SPEED ] = TIME
1000 Fig. 4.2 Timing Chart of
Motor Armature Current and Speed
4. 3 ALLOWABLE FREQUENCY OF OPERATION
OPERATING The allowable frequency of operation is restricted by
TIME (S) I
the SERVOMOTOR and SERVOPACK, and both the
conditions must be considered for satisfactory opera-
100 tion.
k .Allowable frequency of operation restricted by the
SERVOPACK
The allowable frequency of operation is restricted by
the heat generated in the regenerative resistor in the
SERVOPACK, and varies depending on the motor
,0 __ values,types'capacity, JL, acceleration/decelerationcurrentandmotor speed.
If the frequency of operation exceeds t_
_ 60 times/min when JL=0 before the rated speed is
II
6O
reached, or if it exceeds -- cycles/rain when
2100 200 300 m
MOTOR RATED CURRENT (%) JL = JM X m, contact your YASKAWA representative.
Fig. 4.1 Allowable Overload Curve
of SERVOPACK -Allowable frequency of operation restricted by the
SERVOMOTOR
The allowable frequency of operation varies depending
4. 2 STARTING AND STOPPING TIME on the load conditions, motor running time and the
operating conditions. Typical examples are shown
The starting time and stopping time of SERVOMOTOR below. See Par. 4.2, "STARTING AND STOPPING
under a constant load is shown by the formula below. TIME" for symbols.
Viscous or friction torque of the motor is disregarded.
•When the motor repeats rated-speed operation and
Starting Time : being at standstill (Fig. 4.3).
tr=104.7 × NR (JM+JL) (ms) Cycle time (T) should be determined so that RMS
Kt'IR (a-fl) value of motor armature current is lower than the
motor rated current : •
Stopping
Time
II
NR (JM+JL) (ms) T_Ip_ (tr+t/) + I[ts (s)
tf=104.7 X Kt.I_ (a+fl) In'
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