Crompton Controls M20 - Manual (Page 16)

Emotron AB 01-2551-01r4 Selection of Current Transformer 15
Example
• Rated motor current = 12 A.
• Select 10.1-12.5 A from the first column in Table 1.
• This gives:
CTM025 with 2 windings (the motor wire is drawn through the CT’s hole
twice).
In order to ensure an accurate calibration of the M20, it is essential that you use
the correct CTM and apply the exact number of windings in accordance with
the above table.
Table 1 Motors and CT less than 100 A
RATED MOTOR
CURRENT [A]
CURRENT TRANSFORMER TYPE and
NUMBER OF WINDINGS
CTM 010 CTM 025 CTM 050 CTM 100
0.4 – 1.0 10
1.01 – 2.0 5
2.01 – 3.0 3
3.1 – 5.0 2
5.1 – 10.0 1
10.1 – 12.5 2
12.6 –25 1
26 – 50 1
51 – 100 1
NOTE: Normally the appropriate Current Transformer will have been ordered
and shipped with the M20. Check that this is the case; contact the supplier
if in doubt.