Brochure

17
Technical Information – Relays
Precautions
Reset Time (Applicable to Latching Relays Only)
The time that elapses from the moment a relay coil is de-
energized until the NC contacts have closed, at an ambient
temperature of 23˚C. (With a relay having SPST-NO contacts, this
is the time that elapses until the NO contacts have operated under
the same condition.) Bounce time is not included. For the relays
having a reset time of less than 10 ms, the mean (reference) value
of its reset time is specified as follows:
Reset time 5 ms max. (mean value: approx. 2.3 ms)
Set Time
The time that elapses after power is applied to a relay coil until the
NO contacts have closed, at an ambient temperature of 23˚C.
Bounce time is not included. For the relays having a set time of
less than 10 ms, the mean (reference) value of its set time is
specified as follows:
Reset time 5 ms max. (mean value: approx. 2.3 ms)
Shock Resistance
The shock resistance of a relay is divided into two categories:
“Destruction” which quantifies the characteristic change of, or
damage to, the relay due to considerably large shocks which may
develop during the transportation or mounting of the relay, and
“Malfunction” which quantifies the malfunction of the relay while
it is in operation.
Stray Capacitance
The capacitance measured between terminals at an ambient
temperature of 23˚C and a frequency of 1 kHz.
VSWR (Applicable to High-frequency Relays Only)
Stands for voltage standing-wave ratio. The degree of reflected
wave that is generated in the transmission line.
Vibration Resistance
The vibration resistance of a relay is divided into two categories:
“Destruction” which quantifies the characteristic changes of, or
damage to, the relay due to considerably large vibrations which
may develop during the transportation or mounting of the relay,
and “Malfunction” which quantifies the malfunction of the relay
due to vibrations while it is in operation.
a = 0.002f
2
A
where,
a: Acceleration of vibration
f: Frequency
A: Double amplitude
■ Basic Information
Before actually committing any component to a mass-production
situation, OMRON strongly recommends situational testing, in as
close to actual production situations as possible. One reason is to
confirm that the product will still perform as expected after
surviving the many handling and mounting processes in involved
in mass production. Also, even though OMRON relays are
individually tested a number of times, and each meets strict
requirements, a certain testing tolerance is permissible. When a
high-precision product uses many components, each depends
upon the rated performance thresholds of the other components.
Thus, the overall performance tolerance may accumulate into
undesirable levels. To avoid problems, always conduct tests
under the actual application conditions.
GENERAL
To maintain the initial characteristics of a relay, exercise care that
it is not dropped or mishandled. For the same reason, do not
remove the case of the relay; otherwise, the characteristics may
degrade. Avoid using the relay in an atmosphere containing
sulphuric acid (SO2), hydrogen sulphide (H2S), or other corrosive
gases. Do not continuously apply a voltage higher than the rated
maximum voltage to the relay. Never try to operate the relay at a
voltage and a current other than those rated.
If the relay is intended for DC operation, the coil has polarity.
Connect the power source to the coil in the correct direction. Do
not use the relay at temperatures higher than that specified in the
catalog or data sheet.
The storage for the relay should be in room temperature and
humidity.
COIL
1) AC-switching Relays
Generally, the coil temperature of the AC-switching relay rises
higher than that of the DC-switching relay. This is because of
resistance losses in the shading coil, eddy current losses in the
magnetic circuit, and hysteresis losses. Moreover, a phenomenon
known as “beat” may take place when the AC-switching relay
operates on a voltage lower than that rated. For example, beat
may occur if the relay’s supply voltage drops. This often happens
when a motor (which is to be controlled by the relay) is activated.
This results in damage to the relay contacts by burning, contact
weld, or disconnection of the self–holding circuit. Therefore,
countermeasures must be taken to prevent fluctuation in the
supply voltage.
One other point that requires attention is the “inrush current.”
When the relay operates, and the armature of the relay is released
from the magnet, the impedance drops. As a result, a current
much higher than that rated flows through the coil. This current is
known as the inrush current. (When the armature is attracted to
the magnet, however, the impedance rises, decreasing the inrush
current to the rated level.) Adequate consideration must be given
to the inrush current, along with the power consumption,
especially when connecting several relays in parallel.
Double-winding
latching
Single-winding
latching
Contact
Magnetic circuit
Min. set
pulse width
Min. reset
pulse width
Set
coil
Set
Reset
Set time Reset
time
Reset
coil
PCB Relays
Omron A5 Catalogue 2007 1-282 11/9/06 10:16 am Page 17