Panasonic ASCT1F46E User Manual

Automotive Relay User’s Guide

,

Please use the check sheet. 1

Category Section Contents

1. Confirmation
under the
actual use
condition

2. Safety
precautions

3. Selection of

relay type

1. Confirmation
under the
actual use

1. Specification
range

2. Installation,
maintenance

3. Connection When connecting terminals, please follow the internal connection diagrams in the catalog to ensure that

4. Fail-safe If there is a possibility that adhesion, contact failure, or breaking of wire could endanger assets or human

1. Selection In order to use the relays properly, the characteristics of the selected relay should be well known, and the

The rated switching power and life mentioned in the specification and catalog are given only as guides. A
relay may encounter a variety of ambient conditions during actual use result ing in unexpected failure.
Therefore, it is necessary for proper use of the relay to test and review with actual load and actual
application under actual operating conditions.
Use that exceeds the specification ranges such as the coil rating, contact rating and switching life should
be absolutely avoided. Doing so may lead to abnormal heating, smoke, and fire.
Never touch live parts when power is applied to the relay. Doing so may cause electrical shock. When
installing, maintaining, or troubleshooting a relay (including connecting parts such as terminals and
sockets), be sure that the power is turned off.

connections are done correctly. Be warned that an incorrect connection may lead to unexpected
operation error, abnormal heating, and fire.

life, please make sure that a fail-safe system is equipped in the vehicle.

conditions of use of the relay should be investigated to determine whether they are matched to the
environmental conditions, and at the same time, the coil specification, contact specification, and the
ambient conditions for the relay that is actually used must be fully understood in advance.
In the table below, please refer to a summary of the consideration points regarding selection of relay.

Items Consideration points regarding selection

- Select relay with consideration for power source ripple.

- Give sufficient consideration to ambient temperature
and for the coil temperature rise, and hot start.

- When used in conjunction with semiconductors, careful
with the voltage drop.

- When starting up, careful with the voltage drop.

- Note that the relay life is balanced with the life of the
device the relay is used in.

- Is the contact material matched to the type of load? It is
necessary to take care particularly with low level usage.

- The rated life may become reduced when used at high
temperatures. Life should be verified in the actual use
atmosphere.

- It is necessary to be tested and reviewed under actual
use conditions with actual load and actual application.

- Note that ambient temperature and applied voltage
cause the change of operate time and bounce time.

- Note that operate time and release time do not include
bounce time.

- Give consideration that switching life changes
depending on switching frequency.

- Give consideration to performance under vibration and
shock in the use location.

- Confirm the allowable ambient temperature of the relay.

- Selection can be made for connection method with
plug-in type, printed circuit board type, soldering, and
screw fastening type.

- Selection of protection construction can be made for
PCB mounting method such as soldering and cleaning.

- For use in an adverse atmosphere, sealed construction
type should be selected.

- Are there any special conditions?

Coil

Contact

Operate time

Mechanical

characteristics

Other items

a) Rating
b) Pull-in voltage

(current)

c) Drop-out voltage

(current)

d) Maximum continuous

impressed voltage

(current)
e) Coil resistance
f ) Temperature rise

a) Contact arrangement
b) Contact rating
c) Contact material
d) Life
e) Contact resistance

a) Operate time
b) Release time
c) Bounce time
d) Switching frequency

a) Vibration resistance
b) Shock resistance
c) Ambient use

temperature
d) Life

a) Breakdown voltage
b) Mounting,

Connection
c) Size
d) Protection

construction

Panasonic Electric Works

Obihiro Co., Ltd.

Oct. 1

2008: 1stEdition

4. Load,
Electrical life

2

1. General Contact performance is significantly influenced by voltage and current values applied to the contacts (in
particular, the voltage and current waveforms at the time of application and release), the type of load,
frequency of switching, ambient atmosphere, contact switching speed, and of bounce, which lead the
various other damages such as unsuitable operation contact transfer, welding, abnormal wear, increase
in contact resistance. Therefore, please confirm that in actual use conditions such as actual circuit and
actual load or contact our company.

2. Inductive

load

In the case of switching on and off with inductive loads such as coil, magnet crutch, and solenoid, the arc
at switching can cause a severe damage on contacts and greatly shortening of life. In addition, in the
case of switching at a high frequency, a blue-green corrosion may be developed. So, please contact our
company to use it.
If the current in the inductive load is relatively small, the arc discharge decomposes organic matter
contained in the air and causes black deposits (oxides, carbides) to develop on the contacts. This may
result in contact failure. So, please contact our company to use it.

3. Lamp load

Large inrush current enhancing contact welding will be impressed. Its current value is greatly affected by
wiring resistance, switching frequency and ambient temperature. The load current characteristics in
actual circuit and actual use condition must be examined and sufficient margin of safety must be
provided in selection of a relay.
It is dangerous to use a lamp load whose nominal current is small even a large nominal current has been
tested beforehand.
Please contact us when switching at nominal current with a small lamp load (40W or less), because
continuous ON failure may occur due to locking caused by contact-transfer phenomenon when switching
arc is locally concentrated.

4.Electric-

discharge
lamp load

5. LED lamp

load

6. Other lamp

load

7. Motor load

Its load current tends to cause contact welding easily because its inrush current is larger than that of the
regular lamp load. The load current characteristics in actual circuit and actual use condition must be
examined and sufficient margin of safety must be provided in selection of a relay.
It is necessary to check the contact reliability because the load current of the LED load is very small.
Please contact us before use.
Please contact us before use of new structured lamp except for halogen, Electric-discharge lamp, and
LED.
When using of NC contact side of 1C contact for the motor brake, mechanical life might be affected by
the brake current. Therefore, verify in actual use conditions with actual circuit.
Note that larger inductivity of motor may cause contact damage and transfer even the motor load current
is same.

8. Capacitor

load

Note that its load current tends to cause contact welding and contact transfer easily because its inrush
current is generally large which has a small break current and a short time period to reac h an inrush
peak value.
Also, inrush current value is influenced by wiring resistance. Therefore, the inrush current in actual circuit
must be examined and sufficient margin of safety must be provided in selection of a relay.

9. Resistance

load

10. Small

electric

This load causes relatively-less contact damage since its inrush current is not large. Select a relay based
on the rating control capacity, or contact us.
If the switching current is small (2A or less), contact reliability decreases since the contact surface is not
cleaned by switching arc. So, please contact us for use.

current
load

11. Load

polarity

12. Voltage

drop of
power
supply

Electrical life may be affected by load polarity (+/-) connecting to relay contacts. So, please verify them in
actual use polarity.

Under a circuit which inrush current is applied to such as lamps and capacitors, the moment the contact
is closed, voltage drop to the coil, return of relay, or chattering may occur. Note that it may remarkably
reduce the electrical life.

Load

4. Load,
Electrical
life

3

13. Load
voltage

If the load voltage is high, the arc energy which generated at contact switching increases, which may
decrease the electrical life. Therefore, it is necessary to give consideration to the voltage which could
occur in actual use condition.

14. Coil voltage If coil applied voltage gets higher, the relay operate time gets faster. However, contact bounce gets also

larger so that the electrical life may decrease.

15. Coil

short-pulse
input

When the short-pulse signal is input to the relay coil, the relay movable part may operate a nd touch
lightly to the contact. Therefore, please avoid short pulse input (100ms or less) since it may cause
contact welding due to less contact pressure. Please test adequately, for example when a relay is
operated by external manual switch (such as key switch.)

16. High-

frequency

When the switching frequency is high, the electrical life may decrease. Please confirm if there is a
high-frequent switching caused by abnormal mode in actual use condition.

of switching

17. Low-

frequency

Note that if the contact has not been switched for a long time period, organic film tends to be generated
on the contact surface, which may cause contact instability.

of switching

18. Ambient

Verify in the actual use condition since electrical life may be affected by use at high temperatures.

temperature

19. Connection

of coil surge
absorption
circuit

If resistor, diode, zener diode are connected parallel to decrease the surge voltage when the relay coil
being turned off, the relay release time will get longer and may decrease the electrical life or cause
light-welding.

Load

20. Sneak or

remaining
current

Please test a relay in actual vehicle condition since there is a risk of deterioration at relay function or
switching performance such as slower release time which is caused by sneak current due to diode,
zener diode, capacitor mounted on a vehicle or by remaining current soon after a motor is turned off.

21. Wire length If long wires (a few ten meters) are to be used in a relay contact circuit, inrush current may become a

problem due to the stray capacitance existing between wires. In such case, add a resistor in series with
the contacts.

4. Load,
electrical life

4

22. Contact
protective
circuit

Use of contact protective devices or protection circuits can suppress the counter emf to a low level.
However, note that incorrect use will result in an adverse effect. Typical contact protection circuits are
given in the table below.
Also, note that release time will slow down due to sneak in the circuit and may cause the electrical life to
shorten and slight-welding.

Diode circuit

Circuit

The diode connected in parallel causes the energy stored in the coil
to flow to the coil in the form of current and dissipates it as joule

Features/Others

Devices Selection

heat at the resistance component of the inductive load. This circuit
delays the release time. (2 to 5 times the release time listed in the
catalog)
Use a diode with a reverse breakdown voltage at least 10 times the
circuit voltage and a forward current at least as large as the load
current or larger.
In electronic circuits where the circuit voltages are not so high, a
diode can be used with a reverse breakdown voltage of about 2 to 3
times the power supply voltage.

Diode and zener diode circuit

Circuit

Features/Others It is effective in the diode circuit when the release time is too long.

Devices Selection

In the actual circuit, it is necessary to mount the protective device (diode etc.) in the immediate vicinity of
the load. If it is mounted too far away , the ef fectiveness of the protective device may diminish. As a guide,
the distance should be within 50cm.

Avoid using the protection circuits shown in the figures below.
Although it is usually more difficult to switch with DC inductive loads compared to resistive loads, use of
the proper protection circuit will raise the characteristics to that for resistive loads.

Use a zener diode with a zener voltage about the same as the power
supply voltage

Although it is extremely effective in arc
suppression as the contacts open, the
contacts are susceptible to welding since
energy is stored in C when the contacts open
and discharge current flows from C when the
contacts close.

Although it is extremely effective in arc
suppression as the contacts open, the
contacts are susceptible to welding since
charging current flows to C when the
contacts close.

4. Load,
electrical
life

5. Coil

impressed
voltage

5

23. Connection
of load

24. Short

between
interelectrodes

1. Hot start

voltage

2. Ambient

temperature
characteristic

3. Applied

voltage

Connect the load to one side of the power supply as shown in Fig. (a). Connect the contacts to the other
side. This prevents high voltages from developing between contacts. If contacts are connected to both
side of the power supply as shown in Fig. (b), there is a risk of shorting of the power supply when
relatively close contacts short.

Fig. (a) Good example (b) Bad example
Regarding the following circuit constructions with 2-coil relays (twin relays) or single-pole relays, an arc
between contacts may be generated when breaking of load current depending on the type of load
current, voltage, and load. Please note that or contact us.

＜2 coil relay (twin relay) or two of single-pole relays＞

＜Single-pole relay＞

When using of multipole relays such as 2-coil relays (twin relays), verify insulation and breakdown
voltage between contacts in each pole in order to avoid an accident caused by short.

After continuous applying of current to coil and contacts, if the current is turned OFF then immediately
turned ON again, coil resistance and the pick-up voltage will increase due to the temperature rise in the
coil.
Temperature rise value of coil is greatly affected by circuit board, connected harness, connected
connector, heat dissipation of system/modules, and heat source around relay. Please verif y whether it is
operating properly or inoperative under actual vehicle and actual use con ditions.
Coil resistance and the pick-up voltage will increase when the relay is used in a higher temperature
atmosphere. The resistance/temperature coefficient of copper wire is about 0.4% for 1°C, and the coil
resistance increases with this ratio. On the other hand, coil resistance and the drop-out voltage will
decrease at lower temperature. Coil resistance change decreases with the same ratio at higher
temperature, about 0.4% for 1°C.
Therefore, please confirm the relay operation in every operating tem perature range, with attention to
such temperature characteristic.
The ambient usage temperature should be set as around the relay inside the box because a heat
generated by a relay itself or other instruments causes increase of temperature inside the box.
Note that a coil impression with a voltage greater than or equal to the maximum continuous impressed
voltage may cause temperature rise which could cause coil burning or layer short. Furthermore, do not
exceed the usable ambient temperature range listed in the catalog. Please contact us regarding PWM
control.

Ａ

Load

+

Load

+

B

B side OFF

Load

OFF

Load

+

+

Short current

Arcing

Arcing

5. Coil
impressed
voltage

6. Coil
impressed
circuit

4.Twin-relay
coil
simultaneous
operation

5. Continuous

current

1. Relay drive

by means of
a transistor

6
For relays which have multiple coils such as twin relay for forward-reverse operation of motor, if the coils
are continuously turned on at the same time, the coil temperature may exceed the tolerance in a short
time due to heat generation of each coil. Please contact us before use.

Coil heating due to continuous current applying to coil for extensive time periods will cause deterior ation
in insulation performance for coil.
For such circuit types, please consider the fail-safe circuit design in case of contact failure or breaking of
coil.

1. Connection method

Collector connection method is the most recommendable when the relay is driven by means of a
transistor.
To avoid troubles in use, the rated voltage should always be impressed on the relay in the ON time and
zero voltage be done in the OFF time.

(Good) Collector connection

This is the most common
connection, which operation is
usually stable with.

2. Countermeasures for surge voltage of relay control transistor

If the coil current is suddenly interrupted, a sudden high voltage pulse is developed in the coil. If this
voltage exceeds the breakdown voltage of the transistor, the transistor will be degraded, and this will
lead to damage. It is absolutely necessary to connect a diode in the circuit as a means of preventing
damage from the counter emf. In case of DC relay, connection of Diode is effective. As suitable ratings
for this diode, the average rectified current should be equivalent to the coil current, and the reverse
blocking voltage should be about 3 times the value of the power source voltage. Connection of a diode is
an excellent way to prevent voltage surges, but there will be a considerable time delay when the relay is
open. If you need to reduce this time delay you can connect between the transistor's Collector and
Emitter with a Zener diode that will make the Zener voltage somewhat higher than the supply voltage.

Take care of Area of Safe Operation (ASO).

(Care) Emitter connection

When the circumstances make
the use of this connection
unavoidable, the voltage may not
be completely impressed on the
relay and the transistor would not
conduct completely.

Diode

(Care) Parallel connection

As the power consumption of
the entire circuit increases,
the relay voltage should be
considered.

6. Coil
impressed
circuit

7

1. Relay drive
by means of
a transistor

3. Snap action (Characteristic of relay with voltage rise and fall)

It is necessary for the relay coil not to impress voltage slowly but to impress the rated voltage in a short
time and also to drop the voltage to zero in a short time.

Non-pulse signal

Pulse signal (square wave)

(No good) Without snap action (Good) Snap action

4. Schmitt circuit (Snap action circuit) (Wave shaping circuit)
When the input signal does not produce a snap action, ordinarily a Schmitt trigger circuit is used to
produce safe snap action.

1. The common emitter resistor R

must have a sufficiently small value compared with the resistance of

E

the relay coil.

2. Due to the relay coil current, the difference in the voltage between at point P when T
at point P when T

is conducting creates hysteresis in the detection capability of Schmitt circuit, and care

1

is conducting and

2

must be taken in setting the values.

3. When there is chattering in the input signal because of waveform oscillation, an CR time constant
circuit should be inserted in the stage before the Schmitt trigger circuit. (However, the response speed
drops.)

5. Avoid Darlington circuit connections. (High amplification)
Care must be taken in this circuit due to increase of V

. It does not cause a failure immediately, but it

CESAT

may lead to troubles by using for a long period or by operating with many units.

（No good） Darlington connection

Due to excessive consumption of

power, heat is generated.

(Good) Emitter connection

Tr2 conducts completely.

Tr1 is sufficient for signal use.

A strong Tr1 is necessary.