GMC-I Messtechnik GmbH
15
4.4.4 AC Currents with (Clip-on) Current Transformers
Attention!
!
Prior to closing the primary circuit, verify that the secondary
circult is closed. If current transformers are operated in open
state on the secondary side, e.g. due to defective or not con-
nected leads, due to a blown fuse because of prior overload,
or due to a wrong position of the range switch (not on the cur-
rent range), dangerously high voltages can appear at the con-
nection terminals. Therefore, first check that the current circult
of the measuring instrument and the secondary winding of the
transformer which is connected to the instrument form an
uninterrupted measuring circuit. This can be done for all mea-
suring ranges by means of a resistance measurement as
described in chapter 4.6.
Clip-on current transformers allow for measurements of AC currents
without the need to interrupt the operating circuit. For the use of both
bushing type current transformers and clip-on current transformers the
maximum permissible operating voltage is the rated voltage of the cur-
rent transformer. Take into account the additional error in indication.
V~
M
I(A)
