Time Mark 276 series Data Sheet
Model 276B
One primary turn
Model 276A
One primary turn
Loop one leg of AC
line thru transformer
2.00"
B
0.44"
3.90"
1.25"
3.88"
4.50"
C
L
1.25"
.43"
1.95"
2.38"
.19" dia. typ.
Secondary
Space for primary
turn :0 .25" x 0.38"
1.63"
MODEL 276 SERIES
TIME MARK is a division of
Current Transformers
25 to 400Hz
0 to 5 Amp Secondary
Wide Application Range
Agency Approved
DESCRIPTION
Model 276A Current Transformer - A low cost, openframe type current transformer (CT). For use with up to 8
gauge wire, and up to 40 amps on the primary. 2500
VRMS insulation is standard. Frequency range is 25400Hz. The Model 276A CT is CSA Certified.
Model 276B Current Transformer - A ring-type current
transformer for currents from 50 to 1200 amps. The Model
276B 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, #8-32
secondary terminals and mounting brackets. Polarity
markings are stamped on the CT. The Model 276B is UL
Recognized and CSA Certified.
276A APPLICATION DIAGRAM
SPECIFICATIONS
Ratio Part No. Ratio Part No. Burden Ratio Part No. Burden
50:5 276B-50 1.0 300:5 276B-300 12.5
10:5 276A-10 60:5 276B-60 1.0 400:5 276B-400 12.5
15:5 276A-15 75:5 276B-75 1.5 500:5 276B-500 25.0
20:5 276A-20 80:5 276B-80 1.5 600:5 276B-600 15.0
25:5 276A-25 100:5 276B-100 2.0 750:5 276B-750 7.0
30:5 276A-30 150:5 276B-150 5.0 800:5 276B-800 8.0
35:5 276A-35 200:5 276B-200 5.0 1000:5 276B-1000 10.0
40:5 276A-40 250:5 276B-250 12.5 1200:5 276B-1200 12.5
Burden VA @ 60Hz
276A DIMENSIONS
276B DIMENSIONS
276B APPLICATION DIAGRAM
11/2011
© 2011 TIME MARK CORPORATION
Ip Ns
Is Np
300p
60s
5s
1p
325p
65s
5s
1p
275p
55s
5s
1p
TURNS ARE
COUNTED IN
THIS WINDOW
X2 BLACK LEAD
X1 WHITE LEAD
INCOMING
POWER
POLARITY
MARKING
TURNS ARE
COUNTED IN
THIS WINDOW
X2 BLACK LEAD
X2 WHITE LEAD
INCOMING
POWER
POLARITY
MARKING
MODEL 276
TIME MARK is a division of
Current Transformers
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 276.
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 ratio of the current transformer is based on the
condition 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
S E C O N D A R Y T U R N R A T I O
MODIFICATION
Formula:
Where: Ip - Primary amperage
Is - Secondary amperage
Np - Number of primary turns
Ns - Number of secondary turns
Example: A 300:5 current transformer
(in practicality, one turn is dropped from the secondary as a
ratio correction factor).
The ratio of the current transformer can be modified by altering
the number of secondary turns by forward 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.
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
Loading...