Panasonic Corporation Electromechanical Control Business Division
industrial.panasonic.com/ac/e/
Technical Terminology & Cautions for Use (Operation Switches)
Panasonic Corporation 2021
AECTB38E 202110
TYPES OF LOAD
Resistance load
Resistance load is a power factor of 1 (cosφ = 1) where the load is
only for the resistance portion. The displayed switch rating indicates
the current capacity when using AC current.
DC load
Differing from AC, since the direction of current is fixed for DC, the
continuous arc time lengthens when the same voltage is applied.
Incandescent lamp load
Since an inrush current of 10 to 15 times the rated current flows for
an instant when the switch is turned on for the lamp, adhesion of the
contacts may occur. Therefore, please take into consideration this
transient current when selecting a switch.
Induction load
Since arc generation due to reverse voltage can cause contact
failure to occur when there is an induction load (in relays, solenoids
and buzzers, etc.), we recommend you insert a suitable spark
quenching circuit (see figure below).
Circuit example
Notes
r c
R
Switch contact
(1
) r = more than
10
Ω
(2) In an AC circuit,
impedance of R is to be slightly smaller
than impedance of r and c.
r
c
R
Switch contact
Can be used for both AC and DC circuits.
r = R
C: 0.1
μF
R
diode
Switch contact
For DC circuits only.
ZNR
Varistor
Switch contact
Induction load
Can be used for both AC and DC circuits.
Motor load
Contacts may adhere due to the starting current at the start of motor
operation which is three to eight times the steady-state current.
Although it differs depending on the motor, since a current flows that
is several times that of the nominal current, please select a switch
taking into consideration the values in the table below. To make the
motor rotate in reverse, use an ON-OFF- ON switch and take
measures to prevent a multiplier current (starting c reverse
current) from flowing.
Motor type
Type
Starting current
Three-phase
induction motor
Squirrel-cage
Approx. 5 to 8 times current
listed on nameplate
Single-phase
induction motor
Split-phase-start
Approx. 6 times current
listed on nameplate
Capacitor-start
Approx. 4 to 5 times current
listed on nameplate
Repulsion-start
Approx. 3 times current
listed on nameplate
A current that is approximately two times that of the starting current
will flow when reverse rotation is caused during operation. Also,
when using for a load that will cause transient phenomena such as
when operating the motor in reverse rotation or switching the poles,
an arc short (circuit short) may occur due to the time lag between
poles when switching. Please be careful.
Weak Strong
M
M
M
M
M
M
Power
supply
Power
supply
Example of 1-pole motor reverse rotation circuit
Example of single-phase induction motor
(capacitor) strong-weak switching circuit
Example of three-phase motor
reverse rotation circuit
Good wiring
Bad wiring
Good wiring Good wiring
Good wiring Good wiring
Strong
Power
supply
Power
supply
Power supply
Power
supply
Strong
Strong
Weak
Weak
Weak
Capacitor load
In the case of mercury lamps, florescent lamps and the capacitor
loads of capacitor circuits, since an extremely large inrush current
flows when the switch is turned on, please measure that transient
value with the actual load and then either use the product keeping
within the range of the rated current or after verifying the actual
load.
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