MTS Systems MPA-05-460, Manual

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Example 1 shows a typical factory configuration. It shows a ungrounded delta secondary
and there is existing equipment already running. on line. This equipment could be simple
3-phase induction motors where an ungrounded secondary is not an issue. However,
before a 3-phase MPA amplifier, or a machine utilizing 3-phase amplifiers, can be
connected, an isolation transformer, with a grounded secondary must be installed.
Everyone, (OEM's, End users, etc.) must be made aware of this possible situation when a
machine is installed at a customer's site. The power distribution needs to be known and a
transformer, with a grounded secondary, may need to be added to the system before
power is applied.
If you find one of the unacceptable
connections above, you must:
A. Ground the secondary if possible
B. Add an isolation transformer per
acceptable connection (See example
1 below)
Primary
Wye
or
Delta
L1
L2
L3
N (GND)
Acceptable 3-phase Wye Secondary
A1
Primary
Wye
or
Delta
A2
L1
L2
L3
N (GND)
Acceptable 3-phase Delta with high leg
Primary
Wye
or
Delta
A3
L1
L2
L3
(GND)
Acceptable 3-phase Delta with grounded leg
U2
Primary
Wye
or
Delta
Not Acceptable Delta
Primary
Wye
or
Delta
U3
Not Acceptable Delta
Primary
Wye
or
Delta
L1
L2
L3
GND
Not Acceptable Wye
U1
Primary
Wye
or
Delta
Machine 1
Machine 2
L1
L2
L3
GND
Ground
Rod
Add Isolation
Transformer with
Grounded Secondary
1
MPA
Amplifier