6. 3 EXTERNAL CURRENT LIMIT REFERENCE •
CIRCUIT [P-CL, N-CL]
I
Current can be limited from the outside as well as
within SERVOPACK. The external current limit is 300 /
/
used for the following "cases:
• To protect the motor from overloading current when
an abnormal load lock occurs in the load.
2oo
CONTINUOUS
• To change the current limit value according to the ex- CU R R ENT
ternal sequence. RATIO
The current can be limited by multi-stage setting by (%)
100
the use of relays (Fig. 6.6). The same effect can be ob-
tained by giving voltage signals making analog change.
0 [APPROX%--3 --6 --9
_ _ I SETVOLTAGE(V)
_'1 i_ SERVOPACK
VOLTAGECONSTANTf!_]_ f _ _1-44 (a) Current Limit at Forward Side
• SUPPLY+; '_
L__.J
300
Relay:Low levelrelay
Fig. 6.6 Multi-stage Switching of
Current Value at Forward Side
CONTINUOUS 2o0
6.3.1 Method of Giving External Current CURRENT
RATIO
q
Limit Reference (%)
Forward current and reverse current can be controlled 100
independently. The forward current can be controlled
by giving a reverse voltage (0 to --9.0 V) between
SERVOPACK terminals 1CN-@ and @; the reverse cur-
rent can be controlled by a forward voltage (0 to
+9.0V) between terminals 1CN-@ and @. 0 (APPROX_3 6 9
\ 0.6V)
The relation between the rated current of the motor SETVOLTAGE(V)
and applicable motor. The power supply must use an
internal resistance less than 2k12. The input resistance (b) Current Limit at Reverse Side
at SERVOPACKside must be greater than 5kl2. When •
external current is not restricted, contacts between ter- Note : If setting value exceedsmax output current value of
minals 1CN-@ and @ and between 1CN-and O and @ SERVOPACK, maxoutputcurrentvalue becomessaturationvalue.
are opened.
Fig. 6.7 Set Voltage and Current Limit Values
6.3.2 Set Voltage and Current Limit Values
The relationship between set voltages of 0 to +-9.0V
6.3.3 Current Limit when Motor is Locked
and current limit values are shown in Fig. 6.7.
When locking a motor by applying a current limit, de-
termine a current limit value less than 70% of the
rated current of the motor. If the load condition re-
quires a current limit exceeding the rated motor cur-
rent, refer to Par. 6.5. (3), "Overload detection level"
and make sure to unlock the motor before reaching the
trip level.
Note that when the speed reference voltage is less
than tens or so millivolts (affected by setting of GAIN •
of VR4, VR6 and SW3), the motor lock current some-
times pulsates. If this is not desirable, the current pul-
sation can be removed by increasing the speed reference
voltage.
-38-
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