Extech Instruments 380385 Manual page 7

DC Motors
1. Disconnect the motor from the line.
2. To test the brush rigging, field coils and armature, connect the RED lead to the
grounded motor housing and the BLACK lead to the brush on the commutator.
3. If the resistance measurement indicates a weakness, raise the brushes off of the
commutator and separately test the armature, field coils and brush rigging by
connecting one lead to each individually, leaving the other connected to the grounded
motor housing. This also applies to DC Generators.
Testing Single Conductor Cables
1. Completely disconnect the cable
under test from its source and
destination.
2. Connect the test leads to the
cable as shown at right.
Testing Multi Conductor Cables
1. Completely disconnect the cable under test from its source and destination.
2. Refer to the diagrams below for three possible tests.
EARTH
LINE
Testing one conductor to
all of the conductors
Transformer Testing
Transformer tests are performed with the transformer completely disconnected from the
line and the load. Note that the case ground should not be removed.
The five tests listed below will completely test a single-phase transformer. Note that at
least 1 minute should be allowed
between each test.
1. High voltage winding to low voltage
winding and ground
2. Low voltage winding to high
voltage winding and ground
3. High voltage winding to low voltage
winding (pictured at right)
4. High voltage winding to ground
5. Low voltage winding to ground
Core
EARTH
EARTH
LINE
GUARD
Testing one conductor
to earth
Connect the
BLACK lead here
7
Insulation Sheath
GUARD LINE
GUARD
LINE
EARTH
One conductor to all
minus ground
380385 V1.5 3/04
Covering
Connect the
RED lead here