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(1) Incandescent Lamp Load
B remsen
Incandescent lamp
Approx. 1/3 second
Inrush current/rated current:
i/i
≈ 10 to 15
o
(4) Motor Load
i/i
≈ 5 to 10
o
Steady
Starting state
0.2 to 0.5
second
· Conditions become more harsh if
plugging or inching is performed since
state transitions are repeated.
· When using a relay to control a DC
motorand brake, the on time inrush
current, steadystate current and off
time brake current differ depending on
whether the load to the motor is free or
locked.
Inrush Current And The Reverse Voltage
When the motor, capacitance, solenoid and lamp load make, the inrush current is generated, which is several multiple steady state
currents.
When the inductive load such as solenoid, the motor, contactor, the reverse voltage which are from hundreds of to thousands of volts.
Generally in the normal temperature and atmospheric pressure the critical insulation destruction voltage of the air is 200 to 300V.
Therefore if the reverse voltage exceeds this value, the discharge phenomena between contacts will happen.
Both inrush current and the reverse voltage will greatly damage the contacts and obviously shorten the relay life.
Therefore the proper use of the contact protection circuit may increase the life of the relay.
Material Transfer Of Contacts
Material transfer of contacts occurs when one contact melts or boils and the contact material transfers to the other contact.
This often occurs in circuits where electrical arcs are produced at the moment the contacts "make" such as when the DC current is
large for inductive or capacitive loads or when the inrush current is large (several amperes or several tens of amperes).
When material transfer becomes serious, the deformation of the contact surface can be seen by eyes, as shown in Figure 15.
34
(2) Mercury Lamp Load i/i
3 to 5
minutes
The discharge tube, transformer, choke coil, capacitor, etc, are combined in common discharge lamp circuits.
Note that the inrush current may be 20 to 40 times, especially if the power supply impedance is low in the
high power factor type.
(5) Solenoid Load
i/i
≈ 10 to 20
o
Free
Lock
Load
Braking
0.07
to 0.1 second
Note that since inductance is great,
the arc lasts longer when is cut.
The contact may easily burn.
≈ 3
o
Contacts
C
(for high power factor type)
(6) Electromagnetic Contact
Load i/i
≈ 3 to 10
o
1 to 2 cycles
(1/60 to 1/30 seconds)
Figure 10
80618_MAN_IO-LINK IMPACT_12-2019_ENG
(3) Fluorescent Lamp Load
i/i
≈ 5 to 10
o
L
10 seconds
or less
(7) Capacitive Load
i/i
o
1/2 to 2 cycles
(1/120 to 1/30 seconds)
≈ 20 to 40
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