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BUENO ELECTRIC
BUENO ELECTRIC
BUENO ELECTRIC
BUENO ELECTRIC
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Fax: +86-25-51816989
12
When a group of τ value is get, take the relevant smaller value.
②
If the rotor-locked current I and permitted rotor-locked time t are already known, τ could be estimated
according to following formula:
4.3 Instantaneous protection
The instantaneous protection could be realized through judging the amount of current, with setting range of
(4
～
12)I
e.
The instantaneous protection current setting would automatically be halved after motor startup. In this
way, on one hand, the huge startup current of motor could be effectively avoided, and on the other hand,
rotor-locked protection caused by serious overload would be ensured after normal motor startup.
The operation time could be set. For motors controlled by breaker, the setting time is relevantly short. For
motors controlled by contactor, the setting time is relevantly long. The selectable setting time is 0.3 seconds.
4.4 Over-current protection
Over-current protection would automatically exit when motor starts, and would automatically operate when
the startup finishes. When the current is larger than setting current and reaches setting time, over current
protection would output. The over current protection function would be controlled through control character
KG1.2, to select definite-time limit or inverse-time limit mode.
4.5 Zero-sequence current protection
The motor grounding current is dependent on power supply system grounding mode. In ungrounded or
high-resistance-grounded system, fault current is only a few Ampere. In the medium-resistance ground system,
fault current is hundred of amperes.
In most cases, in order to examine the low grounding current, zero-sequence current transformer is often needed
to obtain zero-sequence current.
This device is configured with two types of zero-sequence auxiliary TA, and according to practical condition,
one type could be selected. The linear range of first type zero-sequence TA is
（
20mA
～
5.50A
）
, input through
terminal2 X2:13
～
2X2:14. If this zero-sequence TA is applied to obtain zero-sequence current, the control
