7
MU 03.04.MMM REV.2
1. GENERAL
The regulator works according to binary logic sequence; the switching on and off capacitors banks always starts from the first
bank. The regulator effects a measurement of reactive power with “square method”, therefore it’s important that the regulator is
supplied with two phases and the current signal is brought from the third phase. Simple connection mistake can cause incorrect
working.
2. INSTALLATION
MECHANICAL FIXING
The Regulator should be fixed to a board, (drilling template 91x91mm.) by special accessories included. The plastic case is
insulating self-extinguishing material.
ELECTRICAL CONNECTIONS
The terminal board with male faston 6,35 x 0,8 mm. is available on the back of the regulators. The wiring diagram is shown in
Fig.1 (pag.9). In connecting the voltmetric circuit (V-V), make sure that the voltage of the regulator is the same as the mains
voltage.
HOW TO CHOOSE THE CURRENT TRANSFORMER (C.T.)
•
Use a Current Transformer (C.T.) with 5A at secondary circuit and primary equal or slightly higher than the maximum
current absorbed by the loads. The C.T. must be chosen in such a way to obtain a good current signal in the secondary
circuit. Current values between 0.5 and 5Amps are suitable to obtain good working conditions of the regulator.
•
The C.T. must be good quality (first class) and with power equal or higher to 5VA. If the C.T. has been mounted far from
the equipment, it needs to add to the normal demanded, the power consumed from connection cables (normally 0.2VA per
meter of bifilar lines with 2.5mm
2
c.s.a.) and the power dissipated by others possible devices connected in the circuit.
The equations, used to calculate the real losses, are as below:
R=2x
ρ
ρ
ρ
ρ
xL/S
(
Ω
)
Total resistance of amperometric circuit
P=(R+0.08) x I
2
(VA)
Losses of amperometrical circuit
‘
ρ
ρ
ρ
ρ
‘ is the electrical resistivity ( 0.018 for the copper )
‘
L
’ is the length of amperometric circuit (m)
‘
S
’ is the cross sectional area of cables at the secondary of C.T.
‘
I
’ is max. current at the secondary of C.T.
‘
0
.08’ are the internal resistance of P.F. regulator
•
The cables at the secondary of C.T. have to be of 2,5mm
2
c.s.a. (cross sectional area)
•
The C.T. connection must not be protected with fuses or interrupted by switch.
•
The C.T. has to be connected to the line, upstream to the load and the P.F.Equipment: the C.T., can then measure the
current demanded by the load, inductive and capacitive. Possible capacitors for fixed P.F.Regulation will be connected
downstream to the C.T., as they aren’t used and dimensioned for the compensation of the no load losses of transformer that
supplies the load.
•
It’s important to check that the phase, where the C.T. is connected, is the same that will be connected to terminals of the
main switch, inside the equipment, signed with the letter “R” (L1).
•
Before doing any work on the C.T. circuit, be sure that the C.T. is short-circuited, otherwise dangerous voltages can rise,
bringing to breakdown the C.T.
•
Compensating two or more lines (transformers in parallel), you need to use two or more C.T (.../5) of which the secondary
circuits will supply an add transformer with 5Amps at secondary: connect the current transformers at the same phase.
•
Connecting two or more cables (for load and P.F.Regulator) on the same terminal - phase “R”(L1) - from the general main
switch, it
needs to pass through the hole of the C.T. all the derived cables.
NUMBER OF CAPACITOR BANKS
The banks that can be controlled by the regulator are the following: 3 (series QR3), 4 (series QR4) and 6 (series QR6)
POWER OF CONTROLLED BANKS
For correct operation of the automatic banks, the power ratio per bank should be:
a. equal to each other
(1.1.1.1.1.1)
b. double of the previous bank
(1.2.4.8.16.32)
c. equal or double of the previous bank (1.1.2.2.4.4)
NUMBER OF STEPS
Is determined by the power combination which has been used on single capacitor bank:
Examples:
6 banks in the sequence 1.1.1.1.1.1
make 6 steps
6 banks in the sequence 1.1.2.4.4.4
make 16 steps
6 banks in the sequence 1.2.4.8.16.32
make 63 steps
Note.Where the step sequence is uneven too high a number of steps will result in a high number of switching operations which
will considerably reduce the life of the equipment. With the first step too high hunting may occur which again would
produce excessive wear and reduced life of the components.
•
Normally 8-16 regulating steps is the best solution to adopt.
