K8AB-PA 데이터 시트보기 (PDF) - OMRON Corporation

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K8AB-PA

Three-phase Asymmetry and Phase-sequence Phase-loss Relay

OMRON Corporation 

Q Motor Load Phase Loss during Operation

Phase loss cannot be detected for motor loads during

operation. Use the asymmetry detection function.

Normally, three-phase motors will continue to rotate even if

one phase is open. The three-phase voltage will be induced

at the motor terminals. The diagram shows voltage induction

at the motor terminals when phase R is lost with a load

applied to a three-phase motor. The horizontal axis shows

the motor load as a percentage of the rated load, and the

vertical axis shows voltage as a percentage of the rated

voltage. The lines in the graph show the voltage induced at

the motor terminals for each load when phase loss occurs

during operation. As the graph shows, phase loss cannot be

detected because the motor terminal voltage does not drop

very much even if a phase is lost when the load on the motor

is light. Use the asymmetry detection function to detect

asymmetry in the motor terminal voltages.

Set the operating time carefully because it will affect the time

from when the phase loss occurs until tripping when this

function is used.

Characteristic Curve Diagram

Note: This characteristic curve

shows the approximate values

only.

100

95

90

VST

85

80

VTR

75

70

65

60

55

50

45

VRS

0 10 20 30 40 50 60 70 80 90 100 110

Motor load (as a percentage of rated load)

Note: For phase loss of phase R. VST, VTR, and VRS indicate the motor

terminal voltage at phase loss.

K8AB-PA

ALL DIMENSIONS SHOWN ARE IN MILLIMETERS.

To convert millimeters into inches, multiply by 0.03937. To convert grams into ounces, multiply by 0.03527.

In the interest of product improvement, specifications are subject to change without notice.

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