This section provides overview, applications, and principles of power relays. Also, please take a look at the list of 28 power relay manufacturers and their company rankings.
A power relay is a relay that quickly switches contacts in DC circuits with currents greater than 3 A. In most cases, power relays are mechanical contact relays.
Unlike general control relays, power relays are designed with a robust structure to withstand large currents. Because of their characteristics, they are sometimes used as relays for safety circuits when an abnormally large current flows in a circuit.
Power relays are used as safety circuits to prevent unintentionally large currents from flowing into circuits. Examples of this include the circuits of solar panels and their power feeders, as well as large-powered robots, elevators, and heavy machinery at construction sites.
In addition to safety circuits, relays are also used as the main relay in products that handle large electrical charges. For example, they are used in relays for circuits in charging facilities for electric vehicles and in relays for the main circuits of hybrid cars.
Relays are divided into contact relays and non-contact relays, and power relays fall under the category of contact relays.
When a relay receives an electrical signal from the outside (input), the contacts inside the relay open and close to send a signal to the outside (output). In the case of a relay with contacts, magnetic force acts on the coil inside the relay, physically moving the contacts to open and close the circuit.
In a non-contact relay, the circuit itself is always connected using a semiconductor. When an electrical signal is input, the semiconductor is used to internally conduct the circuit and open and close the contacts.
On the other hand, since this non-contact relay uses the change in conductivity of the semiconductor, it can easily break down once an excessive current flows through it. For this reason, contact relays are used for power relays.
Since a large current flows through a power relay, the amount of heat generated inside the element increases accordingly. For this reason, the inside is filled with gas that has an arc-cooling effect.
Power relays have a life span because they have contacts and are mechanically operated by electromagnetic force. The life expectancy in terms of the number of operations is about several hundred thousand times. If the life is exceeded or excessive shocks are applied, the following failures will occur.
This is a failure in which the coil that provides electromagnetic force to the contacts of the power relay is disconnected. The coil disconnection prevents the electromagnetic force from being generated, and all contacts cease to operate. This failure is relatively easy to detect because there is no "click" sound when the contacts operate. If a lamp is attached, it is possible to check whether the lamp is lit or not.
This failure occurs when an excessive current flows through the contacts of a power relay. The rated current of the contacts is about 5~3A for a typical power relay, and if this is exceeded, there is a risk of welding. The contacts will weld together, leaving the contacts short-circuited and will not open. Diagnose by checking the continuity of the contacts while switching them on and off. If you suspect the contact is a voltaged contact, check to see if voltage is applied to the contact and diagnose.
This problem occurs when a relay contact is worn out or the contact is dirty and no longer electrically conductive. The contacts do not short-circuit by the electromagnetic force of the coil, but remain open. As with welding, check continuity and voltage for diagnosis.
This occurs when the varnish on the power relay coil peels off, causing a short circuit. When the power relay coil is energized, the control power supply itself trips and is found out. Since control circuits often have a number of power relays connected in parallel, it may take some time to detect the problem.
In recent years, direct current (DC) voltages have been used for power relay coils because they are resistant to induced voltages and operate stably even at low voltages.
An AC power supply may be used for power relay coils. This is because the commercial power supply is an AC power source, which eliminates the need for a power supply.
*Including some distributors, etc.
Sort by Features
Sort by Area
This is the version of our website addressed to speakers of English in the United States. If you are a resident of another country, please select the appropriate version of Metoree for your country in the drop-down menu.