Lakeshore Learning Materials 647 - Manual (Page 22)

Lake Shore Model 647 Magnet Power Supply User’s Manual
Setup & Connections 2-6
2.5.8 Remote Sense Connections
The factory configures the MPS to sense, but not control remote voltage. Call Lake Shore to reconfigure the
MPS to control voltage at the load. When using remote sense, the MPS measures voltage at the magnet
instead of at the MPS output terminals allowing a more accurate reading of magnet voltage by eliminating
voltage drops in the leads connecting the MPS to the magnet. If using remote sense, the MPS bases the
voltage at the voltage monitor output on the remote sense voltage instead of the MPS terminal voltage.
Use AWG #24, shielded, twisted pair wiring for sense leads to minimize pickup of external noise. Any noise
on the sense leads may appear at the unit output. Ground sense shield to the MPS back panel.
Make Remote Sense Connections to rear panel detachable terminal block defined in Table 2-4 and Figure 2-
3.
NOTE: The MPS includes a protection circuit which reduces the effect of open sense leads during remote
voltage sensing operation. If the +S lead opens, the output voltage changes because it is sensed between
+OUT and the negative side of the load. If the –S lead opens, the output voltage changes because it is
sensed between the positive side of the load and –OUT. If both leads open, the output voltage is sensed
internally.
The procedure below configures the MPS for remote voltage sensing as shown in Figure 2-4.
1. Turn off the unit.
2. If present, disconnect any wires between the +OUT and –OUT terminals
and the +S and –S connections on the MPS rear panel.
3. Connect the sense leads from the MPS +S and –S connections to the
load. Maintain polarity when making these connections.
CAUTION: Maintain polarity between +S and +OUT and –S and –OUT.
The +S and –S inputs control the output voltage. Improper polarity may
apply damaging voltages to the load.
4. Connect the ground shield to the mounting screw. Make sure that the
shield does not come into electrical contact with either magnet lead.
2.6 MULTIPLE AUTO-PARALLEL SETUP
Connect up to four MPS units in an auto-parallel configuration for increased output current capability. The
maximum total current allowed is the sum of the maximum currents of the individual units. For example four
623 MPS units provide 4*155 = 620 amps total current. The maximum total power is the sum of the maximum
power ratings of the individual units.
Assign each unit a unique address: 1 for MPS 1, 2 for MPS 2, etc. The MPS at address 1 polls the control bus
to determine if an auto-parallel configuration is present and how many MPS units are involved. When multiple
MPS units are present, MPS 1 sends the output current and voltage limits, ramp status, output current step
limit, and other operating parameters to the other MPS units so all units operate identically.
For two MPS configuration, each MPS is programmed for half of the total output current. This is true for the
ramp destination current and ramp rate. Each MPS contributes half the output current required. MPS 1
software polls MPS 2 to determine the total output current. The output voltage, current settings during a ramp,
and instrument status from MPS 1 are reported (since the values are the same for both units.)
An analog signal is also provided for remote activation of the output over voltage protection (OVP) circuit. The
signals connect in parallel so that the output OVP circuits of each MPS activate in unison.
CAUTION: Consult Lake Shore prior to operating multiple MPS units in auto-parallel mode.
MPS Rear View
Maintain
polarity!
Connect -S
to -OUT and
+S to +OUT.
Figure 2-4 Remote Sensing
Connections