Megger TTR25, Инструкция по эксплуатации

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INTRODUCTION
AVTMTTR25 Rev C April 2008
3
provide information about the condition of a transformer’s core. Unwanted
circulating currents, unintentional grounds or even an incipient short circuit can
affect the exciting current and indicate a problem.
Transformer Polarity
Polarity of a distribution transformer becomes of interest in order to determine its
proper connection within a power network. The Megger TTR25 will identify
normal (in phase) and reverse polarity of the single-phase transformers
.
A block diagram of TTR25 is shown in Figure 1-1. The excitation voltage
oscillator applies a 55-Hz test voltage to a transformer under test. There are
three test voltages: 0.5 V, 1.5 V, and 8 V used for transformer testing. Test
voltage selection is based on excitation current required. The required test
voltage is selected automatically.
Input and output transformer voltages are applied to conditioning circuitry. This
circuitry improves signal-to-noise ratio of the test signal, and provides full voltage
range of the test signals at A/D converter inputs.
A/D converter is used to convert the analog measurement signals to their digital
replica. The converted output digital signals are applied to CPLD (complex
programmable logic device) and then are transferred to microprocessor.
The microprocessor is the main part of the TTR test set. It provides proper timing
sequence of operation, gathers and calculates the test result, and interfaces with
peripherals. There are three main peripherals in the TTR25 test set:
RS-232/Printer port, LCD and keypad.
DC power supply converts the primary battery voltage, six Energizer
®
X91 AA-
alkaline batteries, 9 V (nominal), 3135 mAh nominal capacity, into the secondary
DC voltages required for proper operation of the TTR25 test set.