Technical Terminology & Cautions for Use

AECTB38E 201811-T

TYPES OF LOAD

■ Resistance load

Resistance load is a power factor of 1 (cos

φ = 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).

■ 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 current + reverse current) from flowing.

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.

■ 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.

Circuit example

Notes

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.

Switch contact

Can be used for both AC and DC circuits.

r = R

C: 0.1

μF

Switch contact

For DC circuits only.

Switch contact

Can be used for both AC and DC circuits.

rc

R

r

c

R

R

diode

ZNR

Varistor

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

Example of 1-pole motor reverse rotation circuit

Good wiring

Bad wiring

Example of single-phase induction motor

(capacitor) strong-weak switching circuit

Good wiring

Bad wiring

Example of three-phase motor

reverse rotation circuit

Good wiring

Bad wiring

M

M

Power

supply

Power

supply

M

M

Power

supply

Weak

Strong

Strong

Strong

Strong

Weak

Weak

M

M

Power

supply

Power

supply

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