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would a 15kv 300 amp mri power supply
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From: Mark S. Rzeszotarski, Ph.D. [SMTP:msr7-at-po.cwru.edu]
Sent: Thursday, February 19, 1998 1:09 AM
To: Tesla List
Subject: Re: would a 15kv 300 amp mri power supply
Hello All:
>would a 15kv 300 amp mri power supply.....
I worked with one of the early resistive MRI units. The power
supply provided 180 volts at 250 amps. I think it is extremely unlikely
that you have a supply producing 15 kV. Resistive MRI units
circulate the huge currents in four or six large coils to produce the strong
magnetic field (0.15 tesla in my case). MRI requires extremely uniform
magnetic fields, and this is now done most often using superconducting
magnets with a circulating current of 200-300 amps to produce field
strengths in the neighborhood of 1.5T with modern units.
The old resistive MRI power supplies had to have extremely tight
voltage regulation, on the order of several parts per million. The unit we
had used around 90 water cooled paralleled power transistors to regulate the
voltage in a simple series pass type voltage regulator circuit. The biggest
problem we had was trying to keep the cooling water temperature constant
enough for good regulation. A few degrees change in temperature changed the
operating characteristics of the power transistor bank substantially.
Regards,
Mark S. Rzeszotarski, Ph.D.