Time Mark 276B3 Data Sheet
8.5"
1.47"
.45"
1.11"
.28"
1.50"
1.63" dia.
1.80"
.28" x .44" slots typ.
2.75"
3.70"
2.0"
TIME MARK is a division of
MODEL 276B3
9.0"
1.73"
.38"
1.11"
.38"
1.75"
2.08" dia.
1.78"
.28" x .47" slots typ.
2.75"
3.94"
2.0"
3-Phase
Current Transformers
Monitor 3-phase currents
from 50-1200 amps
25 - 400Hz
Brass stud secondary terminals
Agency approved
DESCRIPTION
The Model 276B3 Current Transformer is a ring-type
3-phase current transformer (CT) for currents from 50 to
1200 amps. The Model 276B3 has an accuracy rating
of ±2% for 50-100 amp CT’s and ±1% over 100 amps at
60Hz. This CT also features a 25-400Hz frequency
range and #8-32 brass secondary terminals. Polarity
markings are stamped on the transformer. The Model
276B3 is UL Recognized and CSA Certified.
SPECIFICATIONS
Part No. Ratio Max VA
for 1% accuracy
276B3-50 50:5 2.5 .0153
276B3-100 100:5 2.5 .0306
276B3-150 150:5 7.5 .0459
276B3-200 200:5 10 .0612
276B3-250 250:5 12 .0765
276B3-300 300:5 20 .0919
276B3-400 400:5 25 .122
276B3-500 500:5 5 .0643
276B3-600 600:5 10 .0771
276B3-750 750:5 15 .0964
276B3-800 800:5 15 .1030
276B3-1000 1000:5 20 .1290
276B3-1200 1200:5 25 .1540
Secondary Winding
Resistance at 167º F
DIMENSIONS: 500 - 1200 Amps DIMENSIONS: 50 - 400 Amps
11/2011
© 2011 TIME MARK CORPORATION
Ip Ns
Is Np
300p
60s
5s
1p
INCOMING
POWER
POLARITY
MARKETING
TURNS ARE
COUNTED IN
THIS WINDOW
X1 WHITE LEAD
X2 BLACK LEAD
H1
INCOMING
POWER
POLARITY
MARKETING
H1
TURNS ARE
COUNTED IN
THIS WINDOW
X1 WHITE LEAD
X2 BLACK LEAD
325p
65s
5s
1p
275p
55s
5s
1p
MODEL 276B3
TIME MARK is a division of
3-Phase Current Transformer
READ ALL INSTRUCTIONS BEFORE INSTALLING, OPERATING OR SERVICING THIS DEVICE.
KEEP THIS DATA SHEET FOR FUTURE REFERENCE.
GENERAL SAFETY
POTENTIALLY HAZARDOUS VOLTAGES ARE PRESENT AT THE TERMINALS OF THE MODEL 276B3.
ALL ELECTRICAL POWER SHOULD BE REMOVED WHEN CONNECTING OR DISCONNECTING WIRING.
THIS DEVICE SHOULD BE INSTALLED AND SERVICED BY QUALIFIED PERSONNEL.
Installation Instructions
Primary Turn Ratio Modification
The nameplate of the current transformer is based on the
condition of that the primary conductor will be passed once
through the transformer window. This rating can be reduced
in even multiples by looping the conductor two or more times
through the window. A transformer having a rating of 200 to 5
amps will be changed to 50 to 5 amps if four loops or turns are
made with the primary cable as illustrated.
Nameplate
Ratio
100:5 100:5 400:5 400:5
150:5 150:5 500:5 500:5
200:5 200:5 600:5 600:5
300:5 300:5 800:5 800:5
Nameplate
Ratio
100:5 50:5 400:5 200:5
150:5 75:5 500:5 250:5
200:5 100:5 600:5 300:5
300:5 150:5 800:5 400:5
Nameplate
Ratio
100:5 25:5 400:5 100:5
150:5 37.5:5 500:5 125:5
200:5 50:5 600:5 150:5
300:5 75:5 800:5 200:5
1 Primary Turn
Actual
Ratio
2 Primary Turns
Actual
Ratio
4 Primary Turns
Actual
Ratio
Nameplate
Ratio
Nameplate
Ratio
Nameplate
Ratio
Actual
Ratio
Actual
Ratio
Actual
Ratio
Secondary Turn Ratio Modification
Formula:
Where: Ip - Primary amperage
Is-Secondary amperage
Np-Number of primary turns
Example: A 300:5 current tranformer
(in practicality, one turn is dropped from the secondary as a
ratio correction factor).
Ns-Number of secondary turns
The ratio of the current transformer can be modified by altering the
number of secondary turns by foward or back-winding the
secondary lead through the window of the CT.
By adding secondary turns the same primary amperage will result
in a decrease in secondary output. By subtracting secondary turns
the same primary amperage will result in greater secondary
output.
Again using the 300:5 example, adding 5 secondary turns will
require 325 amps on the primary to maintain the 5 amp secondary
output, or
Deducting 5 secondary turns will only require 275 amps on the
primary to maintain the 5 amp secondary output, or
The above ratio modifications are achieved in the following
manner.
• To add secondary turns, the
white lead should be wound
through the CT from the side
opposite the polarity mark.
• To subtract secondary turns,
the white lead should be wound
through the CT from the same
side as the polarity mark.
TROUBLESHOOTING
Should this unit fail to operate properly, contact the manufacturer
at 800-862-2875.
WARRANTY
This product is warranted to be free from defects in materials and
workmanship for one year. Should this device fail to operate, we
will repair it for one year from the date of manufacture. For
complete warranty details, see the Terms and Conditions of Sales
page in the front section of the Time Mark catalog or contact Time
Mark at 1-800-862-2875.
11/2011
© 2011 TIME MARK CORPORATION
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