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hello, I have managed to obtain a measured step response (speed in revs/sec vs time)of a BLDC motor system (motor, driver circuit) and now need to obtain a transfer function in order to design a controller in matlab. Does anybody know how to work out a systems transfer function from a step...

Hello, I am trying to design some pi and t attenuators using passive components. I can design quite easily for a matched source and load impedance but I'm having trouble with a mismatched source and load. Is there any methods to match the source and load impedances? Will I have to somehow...

Hello, I'm trying to understand a wien bridge oscillator circuit built using op amps. I've heard of a design that uses an op amp buffer on the output of the oscillator, does anyone know the reason for this buffer? is it to do with amplitude stabilisation? many thanks fg

I have carried out a power survey on a site with a 11KV to 400V transformer feeding several non-linear loads (which are VFDs). They are the most significant non-linear loads. The analyzer provided a graph showing third harmonic voltage distortion on two phases, but none on the other phase. Has...

In carrying out insulation resistance tests on three phase motors, is it possible for the resistance to earth to increase as well as decrease over time? Although over sufficient time it will decrease as the insulation breaks down.

yes we checked the measurements several times. we thought there could be a poor joint in the cable or it has been damaged, but it seems strange that all of the cores have almost the same resistance.

The cable length is approx 20 meters and the cable size is 25mm^2

I have discovered a feed cable (4 core, 3 phase and neutral)that supplies a panel from which several motors are fed from, having a resistance on each core of average 35 ohms. Normally a high resistance would reduce the current, but would it increase it to provide the motors with sufficient power?