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Definition of Automotive Relay Terminology

  • From a safety perspective, the use of the automotive relay requires manufacturers of automobiles and automotive equipment to confirm specifications and conduct evaluation tests. Therefore, these products are for sale to automotive manufacturers and automotive component manufactures only.
  • Please inquire with manufacturers of automobiles and automotive equipment about the specifications of automotive relay mounted in vehicle bodies and equipment.
  • Please understand that safety considerations prevent us from receiving inquiries from or dealing with private customers.

1. Coil (Also Referred to as Primary or Input)

1.Coil Designation

Single side stable type
Non-polarized Polarized

2.Nominal Coil Voltage (Rated Coil Voltage)

A single value (or narrow range) of source voltage intended by design to be applied to the coil or input.

3.Nominal Operating Current

The value of current flow in the coil when nominal voltage is impressed on the coil

4.Nominal Operating Power

The value of power used by the coil at nominal voltage. For DC coils expressed in watts; AC expressed as volt amperes. Nominal Power (W or VA) = Nominal Voltage × Nominal Current.

5.Coil Resistance

This is the DC resistance of the coil in DC type relays for the temperature conditions listed in the catalog. (Note that for certain types of relays, the DC resistance may be for temperatures other than the standard 20℃ 68℉.)

6.Pick-Up Voltage

As the voltage on an unoperated relay is increased, the value at or below which all contacts must function (transfer).

7.Drop-Out Voltage

As the voltage on an operated relay is decreased, the value at or above which all contacts must revert to their unoperated position.

8.Maximum Applied Voltage

The maximum voltage that can be applied continuously to the coil without causing damage. Short duration spikes of a higher voltage may be tolerable, but this should not be assumed without first checking with the manufacturer.

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2. Contacts (Secondary or Output)

1.Contact Forms

Denotes the contact mechanism and number of contacts in the contact circuit.

2.Contact Symbols

Form A contacts
(normally open contacts)
Form B contacts
(normally closed contacts)
Form C contacts
(changeover contacts)
  • Form A contacts are also called N.O. contacts or make contacts.
  • Form B contacts are also called N.C. contacts or break contacts.
  • Form C contacts are also called changeover contacts or transfer contacts.

3.Rated Switching Power

The design value in watts (DC) or volt amperes (AC) which can safely be switched by the contacts. This value is the product of switching voltage x switching current, and will be lower than the maximum voltage and maximum current product.

4.Maximum Switching Voltage

The maximum open circuit voltage which can safely be switched by the contacts. AC and DC voltage maximums will differ in most cases.

5.Maximum Switching Current

The maximum current which can safely be switched by the contacts. AC and DC current maximums may differ.

6.Maximum Switching Power

The upper limit of power which can be switched by the contacts.Care should be taken not to exceed this value.

7.Contact Resistance

This value is the combined resistance of the resistance when the contacts are touching each other, the resistance of the terminals and contact spring. The contact resistance is measured using the voltage-drop method as shown below. The measuring currents are designated.

Test Currents

Rated Contact Current or
Switching Current (A)
Test Current (mA)
1 or more 1,000

The resistance can be measured with reasonable accuracy on a YHP 4328A milliohmmeter. In general, for relays with a contact rating of 1A or more, measure using the voltage-drop method at 1A 6V DC.

8.Maximum Carrying Current

The maximum current which after closing or prior to opening, the contacts can safely pass without being subject to temperature rise in excess of their design limit, or the design limit of other temperature sensitive components in the relay (coil, springs, insulation, etc.). This value is usually in excess of the maximum switching current.

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3. Electrical Performance

1.Insulation Resistance

The resistance value between all mutually isolated conducting sections of the relay, i.e. between coil and contacts, across open contacts and between coil or contacts to any core or frame at ground potential. This value is usually expressed as "initial insulation resistance" and may decrease with time, due to material degradation and the accumulation of contaminants.

  • - Between coil and contacts
  • - Between open contacts
  • - Between contact sets

2.Breakdown Voltage (Hi-Pot or Dielectric Strength)

The maximum voltage which can be tolerated by the relay without damage for a specified period of time, usually measured at the same points as insulation resistance. Usually the stated value is in VAC (RMS) for one minute duration.

3.Operate Time

The elapsed time from the initial application of power to the coil, until the closure of the Form A (normally open) contacts. (With multiple pole devices the time until the last contact closes.) This time does not include any bounce time.

4.Release Time

The elapsed time from the initial removal of coil power until the reclosure of the Form B (normally closed) contacts (last contact with multi-pole). This time does not include any bounce time.

5.Contact Bounce (Time)

Generally expressed in time (ms), this refers to the intermittent switching phenomenon of the contacts which occurs due to the collision between the movable metal parts or contacts, when the relay is operated or released.

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4. Mechanical Performance and Life

1.Shock Resistance

1)Functional

The acceleration which can be tolerated by the relay during service without causing the closed contacts to open for more than the specified time. (usually 10 µs)

2)Destructive

The acceleration which can be withstood by the relay during shipping or installation without it suffering damage, and without causing a change in its operating characteristics. Usually expressed in "G"s. However, test was performed a total of 18 times, six times each in three-axis directions.

2.Vibration Resistance

1)Functional

The vibration which can be tolerated by the relay during service, without causing the closed contacts to open for more than the specified time.

2)Destructive

The vibration which can be withstood by the relay during shipping, installation or use without it suffering damage, and without causing a change in its operating characteristics. Expressed as an acceleration in G’s or displacement, and frequency range. However, test was performed a total of six hours, two hours each in three-axis directions.

3.Mechanical Life

The minimum number of times the relay can be operated under nominal conditions (coil voltage, temperature, humidity, etc.) with no load on the contacts.

4.Electrical Life

The minimum number of times the relay can be operated under nominal conditions with a specific load being switched by the contacts.

5.Maximum Switching Frequency

This refers to the maximum switching frequency which satisfies the mechanical life or electrical life under repeated operations by applying a pulse train at the rated voltage to the operating coil.

Notes:
1. Except where otherwise specified, the tests above are conducted under standard temperature and humidity (15℃ to 35℃ 59℉ to 95℉, 25 to 85%).
2. The coil impressed voltage in the switching tests is a rectangular wave at the rated voltage.

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Catalog Download

RELATED INFORMATION Title Language File size Update
用語説明
車載用リレー
JP 149.5KB June 30, 2013
Definition of Relay Terminology
Automotive Relays
EN 47.7KB August 31, 2012
用语说明
车载继电器
CN-Simplified 672.9KB August 20, 2013

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Automotive Relays