Updated Tests on the Original Mini-MRA

Updated Tests on the Original Mini-MRA

(6-27-96)

I. Updated Tests on the Original Mini-MRA

A new breadboard of the original Mini-MRA was put together, using all new parts. The test circuit is shown in Figure (1). A 620 pF silver mica capacitor was used as C1, since the 680 pF was no longer available. Thus the resonance frequency was a bit higher. Previous testing had shown that if the current sensing resistor (R_S) was placed between the two reactances of this series circuit, it was possible to directly measure the enhanced circulating current in the system. At resonance, the ordinary line current is generally determined by the DC resistance in the line since reactances are generally cancelled out. This does not mean that reactive voltages and currents are not present --- they are! Since the reactive voltages and currents are now 90° out-of-phase, there is no power dissipation. Both reactive voltages are reactive currents are 180° out-of-phase, thus they do not appear in the line RMS measurements, per se. However, the high reactance voltages can be measured across each reactance and the high reactive current is possible being measured across R_S (in scope measurements).

The present circuit and test results are given in Figure (1) and Tables (1) and (2). The data is self-explanatory.

II. Conclusions

Tests of the original Mini-MRA continue to indicate that these results are real and there is better than 10X power gains in these circuits (depending upon operating conditions). It would be nice if those of you who have received the pulse transformer (or your equivalent) to try these tests. One caution: you must use reactive sources and loads!

Figure 1: Circuit Used

Table 1: Philips Model PM 3214 Scope

Scope Tests:

V_G = 4V (pk-pk) ~ 2.8 V (rms)

I_G = V_G /R_G~ 2.8 / 5 x 10³ ~ 0.56 mW (rms)

P_in~ 2.8 c 0.56 ~ 1.57 mW (rms)

V_out = 5.8 V (pk-pk) ~ 4.1 V (rms)

i_out = V_out / R_L ~ 4/1 / 4.1 ~ 16.8 mW (rms)

P_out ~ 4.1 x 4.1 ~ 16.8 mW (rms)

P.G. = Pout / P_in~ 16.8 / 1.57 ~ 10.7 X

Also:

V_C1 = 28 V (pk-pk) ~ 19.8 V (rms)

V_L1 = 30 V (pk=pk) ~ 21.2 V (rms)

i_circ = V_RS / RS ~ 27 mV (pk-pk) / 3.3 Ohms ~ 19.1 mV (rms) / 3.3 ~ 5.8 mA (rms)

i_circ/i_G ~ 5.8 / .056 ~ 10.4 X (Same order as P.G.!)

Note: All waveforms are good sinusoidals!

Table 2: RMS Digital Voltmeter Tests

Parameter Fluke 87 Micronta 22-198U Micronta 22-191

V_G1.6 V 1.61 V 1.35 V

i_G0.32 mA 0.32 mA 0.27 mA

P_in0.52 mW 0.52 mW 0.36 mW

i_line0.32 mA < 0.5 mA < 0.5 mA
R_sense1.5 Ohm 1 Ohm 1 Ohm

V_out2.3 V 2.3 V 1.93 V

i_out2.3 mA 2.3 mA 1.93 mA

P_out5.3 mW 5.3 mW 3.7 mW

P.G. 10.2 X 10.2 X 10.3 X

Note: V_G is 'tuned' by f_o for minimum.

Remarks ~

(1) i_G = V_G /R_G = V_G / 5 x 10³

(2) i_line is read at point X using the mA range of the DVM (with R_sense as shown)

(3) R_L was made 1 Kohm to enable an i_out reading directly related to V_out.

(4) While the Fluke 87 and Micronta 22-198U meters read rather closely, the Micronta 220191 reads somewhat lower. However, all power gains (P.G.) are close. This again confirms that power gains determined using most DVMs outside of their calibrated ranges probably are valid provided that resistive sources and loads are used with good sinusoidal waveforms.