Advertisement
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.
A1
Acceptable 3-phase Wye Secondary
Primary
Wye
or
Delta
U1
Not Acceptable Wye
Primary
Wye
or
Delta
22
L1
L2
N (GND)
L3
Acceptable 3-phase Delta with grounded leg
A3
Primary
Wye
or
Delta
L1
L2
L3
GND
U3
Not Acceptable Delta
Primary
Wye
or
Delta
1
Primary
Wye
or
Delta
Ground
Rod
A2
Primary
Wye
or
Delta
L1
(GND)
L3
L2
Not Acceptable Delta
U2
Primary
Wye
or
Delta
Machine 1
Machine 2
Transformer with
Grounded Secondary
Acceptable 3-phase Delta with high leg
N (GND)
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)
MPA
L1
Amplifier
L2
L3
GND
Add Isolation
L3
L2
L1
Advertisement
