Capacitor Bank Installations Flashcards
Why is a capacitor bank installed?
To correct the power factor of various inductive loads, and reduce the demand on the line.
When sizing feeders for capacitor banks what must be considered?
The wires should be sized to handle at least 135% of the total rated load of the bank.
How long may tap conductors be?
7.5 m. after this, they will be the same size as the feeders and not be considered a tap.
What is the maximum size overcurrent protection for a capacitor bank?
250% of the rated load of the bank. If it does not match an O/c value, then round down.
Does a capacitor produce significant heat? How does this affect how they are mounted?
Almost no heat as they are nearly entirely reactive. They can be mounted in a variety of ways as they do not pose a fire hazard under normal operating conditions.
Capacitors must have a discharge circuit, what are the requirements for 750 V or less circuits and more than 750 V circuits?
750 or less = cap must drain to 50V or less in 1 min,
more than 750 = cap must drain to 50V or less in 5 min.
May motor windings be used as a discharge resistor?
Yes, if there is no disconnect between the capacitor and motor.
If a capacitor bank is mounted on the line side of a motor, what is one important consideration?
When the motor is shut down the capacitor will provide leading vars to the rest of the system.
When a capacitor bank is connected on the load side of a motor controller, what is a very important consideration?
The overload devices must be resized as the line current will be less.
Where is the lower current obtained from power factor correction evident?
only on the line side of the capacitor bank.
What considerations must be taken in the installation of a capacitor bank disconnect?
It must be within sight and not more than 9 m, unless capable of being locked open.
If an enclosed type contactor is used to disconnect a capacitor circuit, what must it be rated for? Otherwise what must the disconnect be rated for?
150% of the capacitor load (enclosed type contactor),
Otherwise 135% of the capacitor load.
