4-47
Commercial power source switching(CS)
This function is used for systems with an excessive amount of starting
torque requirements. The motor would be started direct-on-line and then
when the motor had started the inverter would take over. This function
is comonly used to reduce the costing of the inverter. For example, a system may
require 55kW to start but only 15kW to run at constant speed. Therefore, a 15kW rated inverter would be
sufficient when using the commerical power source switching. Assign 14(CS) to an intelligent input terminal.
Using the example below. When the motor has been started direct-on-line, Mg2 is switched OFF and Mg3 is
switched on. With the Forward command to the inverter already on the CS terminal is switched on and Mg1 is
closed. The Inverter will then read the motor RPM and when the CS terminal is switched OFF the retry wait
time (b003) is started.
Once the wait time has elapsed the inverter will then start and match the frequency which is set (b007).
When the Earth Leakage Breaker (ELB) trips on ground fault, the commercial circuit will not operate. When a
backup is required, take the supply from the commercial circuit ELBC.
For FWY, RVY, CSY, use control relays. The sequence above is reference to the circuit and timing diagram
below.
If an over-current trip occurs when frequency matching, extend the retry wait time (b003).
When the power is supplied to the inverter, also it is possible to activate retry operation too. In this case,
follwing CS terminal is out of necessary. For more information, refer to Reset(RS).
Connection figure example and timing on commercial power source switching
INV commercial power source switching
commercial power source INV switching
b003
: retry waiting time
b007
: frequency setting to
match
C001-C005 : Intelligent input terminal
Relation code
Chapter 4 Explanation of function
Mg2
R
S
T
U
V
W
O
L
FW
RV
CS
CM1
AL1
AL2
AL0
THRY
Mg1
Mg3
ELBC
NFB
FWY
RVY
CSY
H
Frequency matching and
operation
Motor
Mg1
Mg2
Mg3
FW
ON
ON
ON
ON
Operation
20ms
over
b003
retry waiting time
Normally set for 0.5-1 seconds
Interlock time of Mg2 and
Mg3
OFF
Inverter output frequency
CS
ON
ON
ON
ON
Inverter
output frequency
CS
ON
Operation
Mg1
Mg3
FW
Mg2
