Tips For Making Precise Ratio Measurements - AEMC DTR 8510 User Manual

As in VT/PT, the CT test may be run as many times as needed by pressing
the TEST button.
The measurement records can be saved in Manual or Auto mode as in
VT/PT mode.
The CT remains active until the configuration is changed. Powering the
instrument down and turning it back on will not change the Test Type.
5.3

Tips for Making Precise Ratio Measurements

The DTR Model 8510 is designed for step-down transformers. It sources
®
low voltage on the primary. It starts with a fraction of the final source
voltage and checks the secondary voltage.
If it exceeds the primary by a pre-determined value, the safety feature stops
the measurement. The recommended procedure is to reverse the leads in
these circumstances so that the primary of the transformer is connected
to the H cables and the secondary of the transformer is connected to the
X cables.
CAUTION: It is important to check that the H cables are connected to
the primary side and the X cables are connected to the secondary side
of the transformer before the test begins.
• Always verify the integrity of the cable connections and reposition
the clips as necessary for robust and low-resistance connections.
Inspect the transformer terminals for dielectric coatings, fungus, dirt
or corrosion.
• Running a continuity test before the ratio test will provide a useful
way to check windings and connections.
• When testing polyphase transformers, keep in mind that in some
cases, the measured ratios must be multiplied or divided by √3.
Refer to § 6 for polyphase connection diagrams and associated ratio
equations.
Digital Transformer Ratiometer DTR
Shop for AEMC products online at:
Model 8510
®
ShopAEMC
www. .com 1.877.766.5412
35