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Spindle Amplifier Shunt Loads
Regenerative energy during deceleration causes the normal voltage on the amplifiers bus to
increase. The amount of energy is application dependent and relates to total inertia. In
general the amplifiers internal shunt load can dissipate this energy within the constraint that
the load inertia is not more than 20 times that of the rotor but this is a guideline. The
deceleration rate of the load determines the rate that voltage rises in the bus capacitors.
The voltage on the bus is sensed and when it becomes too high a solid state device turns on
and causes a load to be placed in parallel with the bus. There are three protection devices
that are used to protect the amplifier from this application dependent loading. The shunt loads
are thermally protected to 85° maximum. There is a fuse in series with the shunt load that
limits the average power in the shunt. If this fuse blows, another circuit measures the bus for
an even higher voltage, and a high bus fault occurs and disables the amplifier.
For 230 volt amplifier products the shunt is turned on at 400 Vdc and turns off at 360 Vdc. A
hi-bus fault occurs if the bus goes over 440 Vdc.
For 460 volt amplifiers the shunt is turned on at 780 Vdc and turns off at 750 Vdc. A hi-bus
fault occurs at 860 Vdc
MODEL
MPA-25
MPA-35
MPA-50
MPA-75
MPA-50-460
EXTERNAL SHUNT
LOAD
EXS-50-230
EXS-100-230
EXS-50-460
26
Load
Fuse
ohms
amps
12
MDL-5
12
MDL-5
12
MDL-6
4
LPCC-15
16
LPCC-8
8.0
MDL-7
4
LPCC-15
16
LPCC-8
Peak
Bus Cap
amps
(min)
MFD
33.3
4400
33.3
6000
33.3
12000
100
12000
49
3000
50
100
49
Continuous
Watts
1000
1600
1600
2000
2000
4000
8000
2400
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