Figure 27, Figure 28, Power connections (continued) – Precision Control Systems 3629C User Manual
Page 21
MODEL 3629C
17
04/10/2007
POWER CONNECTIONS (Continued)
FUSES
LINE 1
LINE 2
LINE 3
LOAD 1
LOAD 2
LOAD 3
TO
3 PHASE SUPP
LY
A
B
C
4 WIRE WYE LOAD
DELTA - 4 WIRE
WYE XFRMR
X
X
1 2
C
LO
S
E
D
Mode Switch
Note: It is recommended that the load and controller be protected by 3 class
"T" or "Semiconductor” fuses. Choose a fuse size approximately 120 to
125% of the current rating of the controller.
DELTA-WYE TRANSFORMER - With WYE load
Using a Delta primary to a 3 wire Wye secondary transformer into a wye load with an SCR
controller is not recommended. If the load across any two legs would happen to open, the
high voltages induced across the primary would almost certainly cause the SCR's to fail.
Using a fourth wire, to connect the junction of the secondary Wye to the junction of the Wye
load, would eliminate this problem.
See Replacement Parts sections.
Figure 27. In-line connections to delta-wye transformer coupled 4 wire wye load.
X
X
1 2
C
LO
S
E
D
Mode Switch
DELTA-WYE TRANSFORMER - With DELTA load
Applying a Delta load to the Wye secondary would be less likely to create the same problem,
as two loads would have to open to induce high voltages across the primary.
DE
LT
A
LOA
D
DELTA WIRE
WYE XFRMR
FUSES
LINE 1
LINE 2
LINE 3
LOAD 1
LOAD 2
LOAD 3
TO
3 PHASE SUPP
LY
A
B
C
Figure 28. In-line connections to a delta-wye transformer couple delta load.