Jetter JM-208-480-OEM, Руководство пользователя

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5 Technical Data
40 Jetter AG
For this calculation it is important that the following parameters are programmed
correctly:
– continuous rated current (which is the minimum of the continuous rated motor
current and servo amplifier current)
– overload factor
– and time constant of the motor
The I²t calculation must be activated by JetSym or by the PLC program.
It is possible to parameterize the warning level.
The error level (error 30) is set to 100 %.
The I²t value is readable in a register of JetMove 208-480 through JetSym or the
PLC.
The digital servo amplifier JetMove 208-480 calculates the percentage of motor
power loss according to the following formula:
x(t) = displayed value of motor power loss in %
t = Time since start of motor running it with the average current (in seconds)
T = Motor time constant (in seconds)
The formula shows that the 100 % value will never be reached as long as the average
motor current is lower than the nominal current of the motor.
Further, calculating always starts by 0 (at t = 0, the result of the equation is 0). After
some time that is by far longer than the motor time constant, the result does virtually
not change any more.
The time till error stop (x = 100 %) is a result of the following formula:
After reset, the values of the important parameters are:
With these parameters the 100 % error level will be reached if, for example the motor
is run by a current of 16 A for about 8 minutes and 30 seconds.
Continuous rated current: 8 A
Overload factor: 2
Motor time constant: 1800 s (30 min.)
x t
( )
100%
average motor current
rated current
-----------------------------------------------------
 
 
2
×
1 e
t
T
--- –
–
 
 
 
×
=
t T 1
rated current
average motor current
-----------------------------------------------------
 
 
2
–
ln
×
– =
Important
Because of the fact that after reset the I²t calculation always starts with zero, the
motor overload calculation is wrong if the motor is already hot when the digital
servo amplifier JetMove 208-480 is switched on (i. e. at the time of parameters of
I²t calculation are written after switching on 24 V logic power supply).