4171
Mach4 General Discussion / Re: WHATS THIS ERROR..??? Clearing a spurious limit hit latch event,
« on: June 30, 2018, 07:11:49 AM »
Hi,
this is probably a bit off topic but here goes.....
I have stated that a VFD often requires line reactors, essentially high inductance filters to accommodate the current pulses that occur in the rectifier/capacitor input circuit.
I have attached two pics, one of the rectifier/capacitor circuit (representative) and its output voltage. Note the ripple on the DC. The second pic is the Fast Fourier Transform (FFT)
of the output voltage waveform. Note the spectral components at the 2nd, 4th, 8th and 10th harmonics. Low order harmonics like this require a highly inductive filter because of the low
frequencies involved.
I have also stated that a phase controlled bridge such as OP is using is noisy and requires line filters capable of filtering higher frequencies. Accordingly I have attached another two pics,
the first a circuit of a phase controlled bridge rectifier (representative). Note that the gate drive voltage sources are low voltage pulses to turn the SCRs on. The output voltage of the bridge
is also shown. Now look at the second pic being the FFT of the output voltage. Note how the harmonic distortion extends all the way out to over 100kHz.....noisy as hell!
Craig
this is probably a bit off topic but here goes.....
I have stated that a VFD often requires line reactors, essentially high inductance filters to accommodate the current pulses that occur in the rectifier/capacitor input circuit.
I have attached two pics, one of the rectifier/capacitor circuit (representative) and its output voltage. Note the ripple on the DC. The second pic is the Fast Fourier Transform (FFT)
of the output voltage waveform. Note the spectral components at the 2nd, 4th, 8th and 10th harmonics. Low order harmonics like this require a highly inductive filter because of the low
frequencies involved.
I have also stated that a phase controlled bridge such as OP is using is noisy and requires line filters capable of filtering higher frequencies. Accordingly I have attached another two pics,
the first a circuit of a phase controlled bridge rectifier (representative). Note that the gate drive voltage sources are low voltage pulses to turn the SCRs on. The output voltage of the bridge
is also shown. Now look at the second pic being the FFT of the output voltage. Note how the harmonic distortion extends all the way out to over 100kHz.....noisy as hell!
Craig