TOSHIBA
6F9EOlll
7.3 Repetitive Starting
When the motor is started, the repetitive starting protection checks the
starting current and the starting time to see if the temperature rise exceeds
the rotor':; allowable temperature rise.
If the allowable temperature rise of
the rotor is exceeded, this protective function issues a lock signal to
prevent the motor from starting.
The rotor heating caused by a single starting is expressed by the following
equation:
E
.
($)2
.
BRM
..:
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
&)
However,
if
at starting
l(t)
=
1st.
then the following holds:
Tst
B
FE'
RM
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..I . . . . . . . . . . . . . . . . . . .
(6b)
Where Tst:
motor starting time
(set)
(setting value)
TSC: allowable rotor locking time
(set)
(setting value)
9
nM:
allowable rotor temperature rise
(rc)
(fixed at
200°C)
1st: starting current (A) (setting value)
Hence, when there is no margin defined in
(6b)
between the rotor's temperature
rise BR(i;) and the allowable rotor temperature rise
~?RM,
a lock output is
issued.
e
RM
-
8R(t)
5
E
.
(3~
.-
www . ElectricalPartManuals . com
To Next Page
Loading...
