Current Transformers Differential Motor Protection
Description:
Current transformers are a means of determining current flow through the input leads of
A.C. motors.
Construction:
Current transformers consist of laminated iron core with windings of a predetermined ratio
for use with specific metering devices.
Application:
A typical application would be the use of three current transformers, one per phase (Self
Balancing Differential Protection). This provides the ability to monitor each phase of an
incoming line and thereby alert the user to any conditions of unequal current, either in
the power source or in the motor windings. The differences in current may also trip the
off line if requested. Six current transformers may also be used (Conventional
Differential Protection) in which three current transformers are at the motor and three
are at the starter.
Installation:
The current transformers can be supplied and mounted in an oversize main motor conduit
box. The current transformers will be identified by a ratio on the current transformers
nameplate and will include screw type terminals on the secondary terminal.
Selection:
The selection of the current transformers is based upon the ratio the user requires for
matching their meters or related instrumentation.
Availability:
Current transformers are available in wide range of ratios.
Specification:
If current transformers are required by the user the sales order must show the ratio
required at the time of entry.
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