AMI 410 Manual

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INSTALLATION, OPERATION AND MAINTENANCE
INSTRUCTIONS FOR THE AMI
MODEL 410, 411, AND 412
MAGNET POWER SUPPLY PROGRAMMERS
I. INTRODUCTION
The AMI Model 410, 411 and 412 Magnet Power Supply Programmers are a family of electronic
power supply programmers used to control both linear and switching power supplies for
superconducting magnet systems. The basic functions of these three models are identical. The
Model 410 is the basic power supply programmer, the Model 411 provides an indication of
magnet voltage with the programmer and the Model 412 provides the same features as the Model
411 as well as providing a regulated current source for magnet persistent switch heater operation.
The front and rear panels are shown in figures 1 and 2.
The Model 410 is available as either a stand alone cabinet model or in a EIA standard 3 1/2 inch
rack version. The Model 411 and 412 are only available in EIA rack mount versions (3 1/2" x
19"). This manual covers the installation, operation and maintenance of the Model 410, 411 and
412. The readers should ignore the sections of the manual (if any) that do not apply to their
particular instrument as the manual is written to cover all three models.
An important consideration in working with superconducting magnets is to charge the magnet
current linearly in time or in some non-linear way as a function of time. Attempting to inject the
desired function into the current control terminals of an ordinary power supply usually results in a
current oscillation in the magnet due to the interaction of the large inductance zero resistance
magnet with the power supply. Alternatively, since the voltage across a superconducting coil is
V=L*dI/dt, one can also control the magnet current by appropriately controlling the voltage
across the coil. However, the voltage across the coil is not the same as the voltage produced by
the power supply because of the voltage drop in the current leads. Large errors result if the
desired function is simply introduced at the voltage control terminals of the power supply. The
Model 410 family of programmers eliminate these problems by measuring the magnet current (an
external shunt is required), comparing the current to the desired current functions and then
producing the appropriate voltage across the magnet which is necessary to achieve the desired
result. Compensation for the voltage drop in the current leads is achieved automatically with no
adjustments required on the part of the operator. The programmer provides for remote operation
via computer utilizing a proper interface between the computer and the programmer's 25 pin D
connector mounted on the rear panel. Analog voltages corresponding to ramp rate and current
limit are used as inputs and magnet current is supplied as an output at this connector.

A magnet quench protection circuit is incorporated to rapidly reduce the power
supply output voltage to zero in the event a magnet quench is detected. The
function is defeatable from the front panel.
II. SPECIFICATIONS
Input power ............................. 115 or 230 Vac, 50-60 Hz
Rampoutput ............................. 0to5VDC
Charging rate ............................ 0to10Amps/sec
Charging rateranges ..................... 0.1, 1 and 10 Amps/sec
Charging rateadjustment ................ 10turn potentiometer
Current limit ............................. 10turn potentiometer
Current control ........................... Up/Pause/Downswitch
Voltage limit ............................. 10turnpotentiometer
III. INSTALLATION
WARNING: Before energizing the instrument, the earth
ground of the power receptacle must be verified to be at earth
potential and able to carry the rated current of the power circuit.
Using extension cords should be avoided. If one must be used,
however, ensure the ground conductor is intact and capable of
carrying the rated current.
In the event that the ground path of the instrument becomes less
than sufficient to carry the rated current of the power circuit, the
instrument should be disconnected from power, labeled as unsafe,
and removed from place of operation.
This document contains operating instructions as well as
calibration instructions. The calibration procedure is to be
performed only by trained service personnel familiar with electrical
safety precautions and proper energized electrical safety
procedures. Do not perform any operations on any AMI equipment
with the cover removed unless qualified to do so and another
person qualified in first aid and CPR is present.
Do not operate this instrument in the presence of flammable
gases. Doing so could result in a life-threatening explosion.
WARNING: Do not modify this instrument in any way. If
component replacement is required, return the instrument to AMI
facilities as described in section IX of the manual.
Page 2

1. Carefully remove the programmer from the shipping carton and remove all packaging
materials. Inspect the equipment for any physical damage that may have occurred during
shipment.
NOTE: If there is any shipping damage, save all packing
material and contact the shipping representative to file a damage
claim. Do not return the instrument to AMI unless prior
authorization has been received.
2. Install the Model 410 programmer on a flat secure surface or install the Model 411, 412
programmer in a 19 inch rack by securing the front panel to the cabinet rails with
mounting hardware supplied by the cabinet manufacturer. It is recommended to support
the rear of the instrument in some fashion.
3. If the programmer and power supply were purchased as part of a console, they should
already be wired together prior to shipment. In any event, the wiring should be checked
prior to applying power to the equipment.
4. Figure 3 depicts a typical system configuration consisting of a superconducting coil,
energy absorber (optional), power supply and programmer.
5. A suitable power supply for operating your system should be available.
NOTE: The power supply is part of the feedback loop for the
programmer and therefore the noise and stability of the system is a
function of the quality of the power supply. The ideal power supply
has zero phase shift, a voltage control mode where 1 volt input
produces 1 volt output, has zero current ripple and would be much
slower than the programmer time constant (0.1 millisecond,
typically). Some switching power supplies may be too noisy for this
application. AMI recommends the Hewlett-Packard Model 6259B
or Model 6260B, as modified by AMI for use with superconducting
magnets, where an extremely quiet and stable linear power supply
is required. AMI also recommends the Power Ten Model 10100, as
modified by AMI, in applications where more power supply noise
can be tolerated. The modifications performed on these power
supplies includes an output rectifier to protect the power supply
from damage due to transfer of the stored energy in the
superconducting magnet back to the supply.
NOTE: An energy absorber should be installed in a system
where it is important to ramp the magnet down at the maximum
rate (i.e. the shortest time). The magnet discharge rate is
determined by the voltage across the magnet according to the
equation V=L*dI/dt and without an energy absorber, the discharge
voltage is determined by the IR drop in the system power supply
cables and many be as low as 0.1 volt. Since the inductance is
Page 5

typically several Henries, it can take a very long time to discharge
a magnet without an energy absorber. For energy absorber
installation, refer to its reference manual.
6. Ensure the power supply and programmer are unplugged and power switches are in the
OFF position.
WARNING: Superconducting magnets can produce and
extremely large inductive voltages that can be dangerous and
potentially fatal. Ensure that all magnets are completely
discharged and all power supplies deenergized before making or
breaking any electrical connection.
7. Connect the magnet power leads from the energy absorber (or directly from the power
supply if the system does not contain an energy absorber) to the magnet's vapor cooled
current lead connection points.
8. Locate the current shunt leads terminated in banana plugs from the energy absorber (or
power supply if the system does not have an energy absorber) and connect to the jacks
marked CURRENT SHUNT INPUT on the rear panel of the programmer. Ensure proper
polarity by plugging red-to-red and black-to-blue.
9. Locate the leads marked PROGRAM OUT and COMMON from the power supply.
Connect these into the appropriately marked plugs on the rear panel of the programmer.
NOTE: If using a Hewlett Packard power supply with the
programmer, ensure the COMMON lead contains a 750
Ω
resistor
in series with the lead. Refer to the power supply manual.
10. Locate the magnet voltage tap leads (blue and yellow) and connect to the terminal strip in
the programmer rear panel marked MAGNET VOLTAGE INPUT. Connect blue to
positive and yellow to negative (Model 411 and 412 only).
11. Locate the wires on the magnet from the persistent switch heater and connect them to the
terminals marked PERSISTENT SWITCH HEATER CURRENT on the rear panel of the
programmer (red to positive and black to negative) [Model 412 only].
12. Connect an appropriate computer interface to the rear panel computer control connector
J5. Two analog inputs and one analog output minimum is required for computer
operation (optional). A pin out of the 25 pin D-connector appears in Figure 6.
13. Connect the programmer and power supply to appropriate AC power sources.
Ensure the programmer line cord and the power supply are plugged into the
appropriate voltage source. The
Page 6

REFER TO POWER SUPPLY OPERATIONS MANUAL
FOR PROPER POWER SUPPLY STRAPPING FOR
REMOTE PROGRAMMING BY EXTERNAL VOLTAGE, VOLTAGE MODE.
Page 8

programmer may be operated on 110V ac or 220V ac, 50 or 60 Hz. Instruction for
proper wiring (or to change) the input voltage transformer are include in figure 5.
The voltage the unit was wired for from the factory is marked on the rear panel.
IV. DESCRIPTION OF OPERATION
The programmer can be operated in three modes:
Mode A is used to control a magnet by manually ramping the current up and down in a linear
fashion. This will be referred to as the normal mode of operation.
NOTE: Do not connect any electronic device or wiring to the
Ramp Out connector (green) on the rear of the instrument in Mode
A or Mode B operation. This connection can only be used for Mode
C operation.
Mode B is used to control the magnet via computer. Analog ramp rate and current limit
signals are supplied to the computer control connector and an analog representation of magnet
current is read back from the programmer to the computer. Operation in this mode requires
either a DAC/ADC interface card, a GPIB card and controller or RS-232 card and controller.
Mode C allows use of the programmers internal ramp generator for other laboratory uses.
The following paragraphs provide a description of the front panel displays and controls.
1. Power Switch - This switch energizes and de-energizes the programmer. In the POWER
position the programmer is energized and the green POWER LED should be lit.
2. Charge Rate - The RAMP RATE, AMPS/SECOND will select a 0.1, 1 or 10
amperes/second charge rate. The VARIABLE ramp rate is a ten turn potentiometer that
divides the selected range into sub-increments (i.e. 1 amp/sec is controlled from 0.1 to 1
amp/sec).
3. Up/Down/Pause switch - The magnet current can be controlled for ramp up, ramp down,
or pause, depending on the setting of this switch. If the switch is left in the Up position,
the current will ramp up to the Current Limit setting. Allowing the magnet current to be
controlled by the current limit setting produces a constant, highly stable, magnet current.
When the switch is in the pause position, the magnet current can drift slightly depending
on the stability of the ramp generator.
4. The Current Limit is a ten turn potentiometer that will set the upper limit the programmer
will ramp to ( i.e. when using a 100 amp power supply a setting of 9 will limit the magnet
current to approximately 90 amperes). When the current reaches the current limit the
CURRENT LIMIT LED will light. The current limit can be reset at any time. If the
Up/Down/Pause switch is in the UP position the Current Limit will control the current as
follows: If the current limit is moved to a higher value from the locked mode, then the
ramp will restart at the rate set by the RATE dial and RATE RANGE switch until the
Page 12

current limit is reached again. If the current limit is reduced to a lower value, then the
current will ramp down to the lower value at the set rate and lock in at the new current
limit.
5. The Voltage Limit controls the output voltage maximum value. The maximum value is
normally set at 10 volts when the programmer is attached to a 10 volt in/10 volt out power
supply. THIS DIAL SHOULD BE SET TO 10. In some special cases, e.g. short sample
measurements, it might be desirable to limit the voltage. However, any time the voltage
limit light is on the ramp rate will be non-linear and the current will not reach the current
limit linearly. When the voltage limit is reached the red VOLTAGE LIMIT LED will
light.
6. Digital Current Meter - This meter reads the power supply current as read from the current
shunt.
7. The Magnet Voltage indicates the voltage across the magnet. (Model 411 and 412 Only)
NOTE: It is convenient to have the magnet voltage indicating
the positive direction when the current reversing control switch is
in the UP position. If this is not the case, simply reverse the
magnet voltage leads or the magnet supply leads at the vapor
cooled current lead connection. This note applies to systems
utilizing an energy absorber.
Quench Detection - This protection circuit continuously monitors magnet current (when
enabled) and in the event of magnet quench, quickly ramps the power supply output to zero.
This circuit can be reset by placing the switch in the OFF/RESET position momentarily and
then returned to the QUENCH DETECTION position. This protection feature can be
disabled if magnet voltage transients cause the protection circuit to operate when the magnet
has not quenched. To disable this feature put the switch in the down position.
Persistent Switch Heater - The heater is controlled by the key switch. The POWER LED
indicates the control circuit is operational but does not indicate heater operation. The
OUTPUT LED indicates current is being supplied to the heater; i.e. the LED is on when the
heater is energized thereby removing the magnet from persistent mode.
The AMI programmer incorporates a unique stability circuit which makes it compatible with
many power supplies which could not previously be used with superconducting magnets. A
current programmer includes the power supply in a feedback loop. Not only do various
power supplies have different characteristics but the load can be resistive (including a short
circuit) highly inductive, or a combination (series leads, parallel persistent switch). A circuit
which achieves stability (no current oscillations) under all these conditions is difficult to
achieve. The Models 410, 411, and 412 have been designed to achieve this goal. It has been
tested with the HP 6260B power supply as well as the Power Ten 10100 switching power
supply. Other power supplies are expected to work equally well. It should be mentioned that
the programmer cannot improve on the natural dynamic noise level of the power supply.
Page 13

Should any instability occur, the Model 410-412 is equipped with an adjustable damping
circuit. Refer to the Troubleshooting Section VII for more information.
V. OPERATION
1. System Test:
Prior to connecting the power supply cables to the magnet current leads, it may be desired
to preset your magnet controller current limit to the current that corresponds to the rated
central field (i.e. rated current) and check to ensure the controller operates properly. The
first time you use the programmer it is best to test the system on a short circuit rather than
a magnet. This can be done as follows:
a. Ensure the magnet power supply is de-energized and short the output leads from the
power supply together securely.
NOTE: If you have an energy absorber in your system you will
short the output leads of the energy absorber instead of the power
supply.
b. Ensure the key operated PERSISTENCE SWITCH HEATER switch is OFF.
c. Set the VARIABLE ramp rate potentiometer on 10 and the current control switch in
the DOWN position.
d. Set the CURRENT LIMIT potentiometer to the rated current as indicated on you AMI
magnet data sheet.
e. Turn on power to the magnet programmer.
f. Turn on power to the power supply.
g. Place the CURRENT CONTROL switch to the UP position. The current indication
should rapidly increase to the approximate rated current.
h. Adjust the current to the specified value by fine tuning the CURRENT LIMIT
potentiometer. The current limit is now set and you are assured the power
supply/magnet programmer is working properly.
i. Place the CURRENT CONTROL switch to the DOWN position to ramp the current to
zero.
j. Turn off power to power supply and then to the magnet programmer.
CAUTION: Always energize the programmer first, then the
power supply upon system startup and always deenergize the
programmer last on system shutdown to allow the programmer to
always have control of the system. Not doing so could result in
Page 14

voltage/current spikes introduced in the magnet system with could
produce undesirable results.
k. Reconnect the power leads to the vapor cooled current leads.
2. Mode A (normal mode) operation:
a. Place the Computer-Manual switch in the MANUAL position.
b. Place to Up-Pause-Down switch in the DOWN position.
c. Adjust the Voltage Limit to 10, Ramp Rate and Current Limit as desired.
d. Use the charging voltage and inductance in the specification sheet to calculate the rate
from the equation V = L dI/dt.
e. Energize the programmer and the power supply.
CAUTION: Always energize the programmer first, then the
power supply upon system startup and always deenergize the
programmer last on system shutdown to allow the programmer to
always have control of the system. Not doing so could result in
voltage/current spikes introduced in the magnet system with could
produce undesirable results.
f. Enable the quench detection circuit (if desired).
g. Ramp the magnet up or down by using the Up-Pause-Down switch.
h. The various switches (Ramp Rate Range, Ramp Rate, Current Limit, and
Up/Down/Pause ) can be changed at any time. Care should be exercised not to set the
current limit or ramp rate to higher values than can be tolerated by the magnet.
i. To change the current setting (and field) place the ramp up-down switch in the
PAUSE position. Set the rate range switch and rate dial to the charge rate desired and
the current limit to the desired point. Placing the ramp switch to the UP position will
cause the current to ramp up at the desired rate. The current can be stopped, and held
at any time by placing the ramp switch to PAUSE, or can be ramped down at the
chosen rate by flipping the switch to the DOWN position. The desired rate is
maintained provided the charge and discharge voltages demanded by the
superconducting coil (V = L dI/dt) are within the capabilities of the power supply -
diode system. If the ramp switch is left in the UP position the current will ramp up to
the current limit where it will be locked in to a stable current mode.
3. Mode B (computer mode) operation:
a. Connect a cable from your computer interface to the Computer Control connector on
the back of the programmer. The pin connections to the programmer are shown in
Figure 6.
Page 15

b. Place the Computer-Manual switch in the COMPUTER position.
c. Set the voltage limit potentiometer to 10.
d. Energize the programmer and power supply.
CAUTION: Always energize the programmer first, then the
power supply upon system startup and always deenergize the
programmer last on system shutdown to allow the programmer to
always have control of the system. Not doing so could result in
voltage/current spikes introduced in the magnet system with could
produce undesirable results.
e. Enable the quench detection circuit (if desired).
f. Set the ramp rate RANGE switch to the correct rate. Note that the computer does not
control this switch. It must be set manually.
g. The programmer is now under computer control. To control the magnet current the
computer must furnish analog signals (0-5 volts) to the Ramp Rate connections (J5
Pins 1 & 14) and the Current Limit connections (J5 Pins 2 & 15). Five volts on the
ramp rate pins produces 0.1, 1.0, or 10.0 A/S depending on the setting of the ramp rate
range switch on the programmer. Five volts on the current limit pins will set the
current limit to full scale current for the system. Intermediate voltages produce scaled
values for the ramp rate and current limit. In this mode the external Up/Down/Pause
switch is inoperative because it has been disconnected internally and placed in the
"up" mode. This means that the magnet current always ramps up or down to the value
corresponding to the voltage signal from the computer. An opto-isolator signal is
available from the programmer (pins 5 & 18) which can be read to indicate when the
current limit has been reached. An analog voltage is supplied by the programmer (0-5
volts, Pins 19 & 7) which can be read directly by the computer to indicate the current
at any time. One can approximate any current function within the range of the
magnet/power supply system by a sequence of straight lines controlled by the
computer supplied ramp rate voltage and current limit voltage.
4. Mode C (internal ramp generator function) operation:
a. Set up the programmer and power supply as described for mode A operation.
b. Disconnect jumper W2 on the printed circuit board.
c. A linear ramp voltage controlled by the ramp range switch, the variable ramp rate
potentiometer, and the Up/Down/Pause switch is available between the green RAMP
OUT and the black COMMON terminals on the rear panel of the programmer.
d. If your magnet is equipped with a persistent switch be sure that the persistent switch
heater power supply is turned on to charge the magnet.
Page 16

5. ( Model 412 ) Magnet Persistent Mode Operation:
a. Record the current displayed on the Magnet Current meter.
b. Lock the current against the current limit by leaving the current control switch in the
UP position when the desired current limit has been established. Wait for the
inductive voltage across the magnet to reach zero. If the voltage is measured any place
except at the magnet terminals, it is more difficult to tell when the inductive voltage is
zero because the voltage drop in the lead system is added to the inductive voltage.
c. Turn the key operated switch to the OFF position. When the persistence switch heater
is turned off you should allow the switch to cool off for approximately 30 seconds.
This is a safe number. Actually, most AMI persistent switches cool adequately in a
few seconds.
d. A more reliable technique for ramping the current to zero is to program the current to
zero with the ramp down switch. The ramp rate range switch can be increased to
hasten the discharge. The voltage across the magnet should remain zero. A negative
voltage during magnet discharge means the current is decaying and the magnet is not
in the persistent mode. In this case, ramp the current back to the desired value and try
again.
e. To return to the programmed control mode of operation ensure the current limit is set
to the value recorded when you switched into the persistent mode.
NOTE: The best method is to not have moved the current limit
setting after switching to the persistent mode.
f. Turn the power supply back on and put the Up/Down/Pause switch in the Up position.
The current indication should begin ramping up while the voltage across the magnet
remains zero.
NOTE: If You switch the ramp selector to "10" to decrease the
time to ramp the current to the desired value. Be sure to return the
range switch to the appropriate setting before switching out of the
persistent mode.
g. When the current reaches the desired value turn the persistent switch heater ON.
There will be a 10 to 15 second time delay as the switch heats up. You may see a
small voltage across the magnet as the current of the magnet and power supply match
up but this should quickly decay to zero.
VI. CALIBRATION
NOTE: This instrument was calibrated at the factory and should
require no further adjustment for many years. The following
Page 17

information is furnished in the event changes are desired or due to
aging of the components causing calibration errors.
Current Shunt - The calibrations of the programmer are based on the use of a 100 ampere/100
millivolt current shunt, however, shunts of other sizes can be used if the scale factor F =
(shunt amps/volt)/(100/0.1 amps/volt) is applied to the current rates and current limits. For
example, to use a 50 amp, 0.1 volt shunt, F = (50/.1)/(100/.1)-.5. Thus 10 amp/sec rate is now
0.5 x 10 amp/sec = 5 amp/sec and the full scale current limit is 0.5 x 100 amp = 50 amperes.
WARNING: This calibration procedure is to be performed
only by trained service personnel familiar with electrical safety
precautions and proper energized electrical safety procedures. The
Models 410-412 contains high voltages capable of producing
life-threatening electrical shock. Do not perform any operations on
any AMI equipment with the cover removed unless qualified to do
so and another person qualified in first aid and CPR is present.
1. Deenergize the instrument by disconnecting the power plug from the power receptacle.
2. Disconnect the programmer from any power supplies.
3. Remove the instrument cover.
4. Verify the main PCB jumper configuration is as follows:
W1 ............................... JUMPERED
W2 ............................... JUMPERED
W3 ............................... JUMPERED
W4 .................OPEN
W5 ............................... JUMPERED
W6 ............................... JUMPERED
W7 ............................... JUMPERED
W8 ................. OPEN
W9 ................. OPEN
W10 ................ OPEN
W11 ................ OPEN
5. Adjust the STABILITY potentiometer P7 fully counter-clockwise.
6. Place a shorting jumper across the CAL test points on the PCB.
7. Plug in the line cord to the proper voltage source.
8. Place the front panel COMPUTER/MANUAL switch in the MANUAL position.
9. Place the POWER switch to the ON position.
10. Ensure the power LED and the DVM on the front panel are lit.
Page 18

11. Look for any unusual signs of component heating on the PCB
12. Measure the power supply outputs on the PCB at TP +15V, -15V, and +5V with respect
to COMMON.
13. Connect a voltmeter between TP7 and COMMON. Adjust the input NULL potentiometer
P2 until the meter reads 0.000 volts.
14. Connect the voltmeter between TP13 and common. Adjust the CURRent LIMIT pot P12
to obtain 5.000 volts.
15. Connect the voltmeter between TP14 and common. Adjust the VOLTage LIMIT pot P11
to obtain 10.000 volts.
16. Connect the voltmeter between TP15 and common. Adjust the RAMP RATE pot P10 to
obtain 5.000 volts.
17. Place the front panel CHARGE RATE RANGE switch to 10 amperes/second.
18. Place the front panel CURRENT CONTROL switch in the UP position.
19. Turn the front panel VOLTAGE LIMIT potentiometer fully CW (10.0).
20. Connect the voltmeter between TP5 and common. Adjust the VOLTage LIMIT pot P11
to obtain +10.000 volts.
21. Connect the voltmeter between TP3 and common. Adjust the output voltage PROGRAM
OUT pot P6 to obtain 10.000 volts if the programmer is in a system with a HP 6260B
power supply. If the programmer is in a system with a switching power supply, adjust P6
to obtain 5.000 volts.
NOTE: Refer to the power supply manual for the proper control
voltage.
22. Place the front panel CURRENT CONTROL switch in the DOWN position.
23. Connect the voltmeter between TP11 and common. Adjust the ZERO LOCK
potentiometer P8 to obtain 0.000 volts.
24. Deenergize the programmer.
25. Remove the shorting jumper across the CAL test points on the PCB.
26. Connect the programmer to the power supply and energy absorber (if possible). Ensure
the PROGRAM OUT and CURRENT SHUNT terminals on the rear panel are properly
connected to the power supply and current shunt as described in the Installation section of
this manual.
27. Short the current leads of the power supply system.
Page 19