C H A P T E R 7 – T E S T S A N D T E S T C O N D I T I O N S
AT5600 User Manual 98-119 issue 14 Page 165
7.45. DCRT - DC HI-POT Ramp
Where Used
Hi-Pot Ramp testing (to check for insulation breakdown between windings or
between windings and the screen or core) is often specified for power line
transformers or for switched mode power transformers in applications where
safety is important.
It is typically performed between all primary windings connected together, and all
secondary windings plus the screen connected together.
Specifying the Measurement
During the test, a DC target voltage is applied across two groups of windings with
the windings in each group being shorted together. The voltage and current are
monitored throughout the ramp time.
In programming the tester, you may select the voltage (from 100V to 7KVdc), the
current trip level (1A to 1mA), and the ramp up times (1 to 2sec), all to suit the
specification of the transformer under test.
The purpose is to check the safety isolation between windings, windings and
core, or windings and screens, measuring the voltage at which a user specified
current is exceeded, by ramping to a maximum user specified DC voltage.
The operation is to ramp up the test voltage continually monitoring the current to
check it is below the test limit.
If target voltage is reached and the maximum monitored current is not exceeded
the test has "Passed".
If the maximum monitored current is exceeded before the target voltage is
reached the test has "Failed".
Please also see
14.6.41 for specific advice on programming the test, and
10.2.30 for test accuracy specification
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