2-12 Installation
Power Factor
Correction Capacitors
The controller can be installed on a system with power factor
correction (PFC) capacitors. The capacitors must be located on the
line side of the controller. This must be done to prevent damage to the
SCRs in the SMC-Flex controller.
When discharged, a capacitor essentially has zero impedance. For
switching, sufficient impedance should be connected in series with
the capacitor bank to limit the inrush current. One method for limiting
the surge current is to add inductance in the capacitor’s conductors.
This can be accomplished by creating turns or coils in the power
connections to the capacitors.
• 250V — 15 cm (6 in.) diameter coil, 6 loops
• 480…690V — 15 cm (6 in.) diameter coil, 8 loops
Take care in mounting the coils so that they are not stacked directly
on top of each other; stacking will cause a cancelling effect. Also,
mount the coils on insulated supports away from metal parts so they
will not act as induction heaters. If an isolation contactor is used, put
capacitors in front of contactor.
Note: For further instructions, consult the PFC capacitor vendor.
Figure 2.9 Typical Wiring Diagram for Power Factor Correction Capacitors
Figure 2.10 Typical Wiring Diagram for Power Factor Correction Capacitors
and Contactor
L1
L
L2
T
T2
T1
-Phas
In
ut Powe
Br
n
h
Prot
tio
M
-Flex
ontrolle
Pow
r F
to
Correction Ca
acitor
➁ Overload protection is included as a
standard feature of the SMC-Flex controller.
L1/1
L3/5
L2/3
T3/6
T2/4
T1/2
M
3-Phase
Input Power
Branch
Protection
SMC-Flex
Controller
Power Factor
Correction Capacitors
➀
➀ Customer Supplied
➁
➀
➀
➁ Overload protection is included as a standard feature of the SMC-Flex controller.
➂ Energize 1/2 second before start command to SMC.
➂
➃ Open contactor after stopping method is complete.
➂ Energize contactor after up-to-speed.
➃ Open contactor before initiating a stop.
Alternate
➃
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