DTE-M series current injector operating principle based on power regulation in primary circuit of power matching transformer and, accordingly, regulation of output current, which flows through automatic circuit breaker under test. Power output can be regulated by voltage regulator (RNO-SVR) or inbuilt thyristor regulator.
DTE-M allows regulating current value (voltage) with inbuilt thyristor regulator and with this output current has distorted waveform (see. figure 1 oscillogram 1) or using separate voltage regulator (RNO-SVR),then output current will have sinusoidal waveform (see. figure 1 oscillogram 2).
Using RNO-SVR operating mode, thyristor module act as power key and after automatiс circuit breaker operation, when current stops flow through, thyristor module closes and deenergises RNO-SVR.
Oscillogram 1 – Thyristor module operating handle turned on 35º;
Oscillogram 2 – Thyristor module operating handle turned fully clockwise (thyristor regulator fully opened)
Figure 1 – Oscillograms of output current of DTE-M series injector
1. Current regulating with single-phase voltage regulator (RNO-SVR)
This mode assumes presence of RNO-SVR voltage regulator. In this mode thyristor regulator works only as a solid state power relay, which connects during transition voltage through zero, the primary winding of RNO with the input voltage supply.
The current, generated on the RNO-SVR output, has sinusoidal waveform that provides accurate measurement of the output current of the current-meter of the DTE-M series tester.
Smooth regulation of output current.
Measurement accuracy of current – 1.5%
2. Current regulating with inbuilt thyristor regulator (TRT)
The second mode is used for estimating workability protections of automatic circuit breakers with current measurement errors of more than 2.5%.
In this mode, the output current is regulated by inbuilt thyristor current regulator and has pulsed shape waveform with harmonic distortion factor more than 5.
Current measurement error – 3%.