MAGNET POWER SUPPLY SYSTEM 7000
40
DANFYSIK A/S - DK 4040 JYLLINGE - DENMARK.
4.3.21
Load Dump
The Load Dump circuit will dissipate the power stored in magnet connected to the MPS
SYSTEM 7000, if the main AC power suddenly drops.
The Load Dump circuit is designed only with discrete components, because auxiliary power
will disappear when the AC input supply drops.
The Load Dump circuit is capable of dissipating up to 500J in two large power resistors
mounted on the chassis.
The current stored in the magnet will be returned to the Power Amplifier positive or negative
supply line by the two reverse diodes in the Power Amplifier D502 and D518. When the
positive supply line reaches app. 125V, the discrete thyrister Q511 and Q512 will turn Q515
ON. When The FET is ON, the Power resistor is connected across the supply line to dissipate
the magnet energy. The “thyrister” will turn the FET OFF, when supply lines gets below 100V.
Circuit equal to positive line, but transistor of complimentary types protects the negative line.
4.3.22
Auxiliary Voltage and Ground planes
The Amplifier Board is supplied by a ±15V-regulated supply.
The Amplifier Board carries its own +5V supply for the digital interface, interlock and LED’s.
This +5V is regulated from the +15V by U603.
The Ground in the Amplifier Board is divided in five ground planes;
GNDD:
Are ground for ON/OFF/STANDBY circuit, Interlock and digital interface.
GNDA
Are ground for Analog measurements.
GNDP
Are ground for the Output Power Stage.
LGND
Are ground for the Regulation Loop.
GNDDCCT
Are ground for the DCCT circuit.
GNDD, GNDA, and GNDP are connected in one star-point.
LGND and GNDDCCT are connected to GNDA in a star point.
4.3.23
Current Transducer
The Current Transducer delivers a current proportional to the output MPS current measured by the
DCCT head. This module is calibrated with the DCCT head to give exact 0,1A with a 100% output
current.
This circuit contains the following four main functions:
_
A power output amplifier.
_
A zero flux detector.
_
An interlock circuit.
_
A low voltage supply.