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Is there a difference between a car starting relay and an electromagnetic master switch?


The principle of starting relay and electromagnetic master switch is the same. The starting relay is used more frequently and mainly controls the magnetic switch of the starter. The volume is smaller than the electromagnetic switch. The number of electromagnetic switch is relatively less, the volume is relatively large, and the rated working current is relatively large. Starting relay whether it is a car or a big truck, engineering car is one of the necessary relays. And the electromagnetic main switch most only used in large trucks, engineering vehicles above, car application is less. Here's what the starting relay looks like:

There are many models of starting relays and they all look different. But the internal principle is the same, different types of relays and the size of the current is not the same, the starter power is relatively large, so the starting relay working current should be selected larger. The working principle is the same as the ordinary relay, so is the principle of the electromagnetic switch. Both relays are normally open. After receiving electricity, the relay coil generates a magnetic field, which holds the armature firmly. The moving contact on the armature contacts with the static contact on the other end, and the circuit is switched on. When the coil is powered off, the magnetic field disappears and the armature breaks the two contacts under the action of the spring. At this time, the circuit is in the disconnected state.

The above picture shows the application of the starter relay in the circuit. The starter relay is mainly used to avoid the ignition switch being corroded by the high current. In the early years, the power of the starter was small, and many cars used the key switch to start the car directly. With the increasing power of the car starter, the power of the magnetic switch is also increasing, and the contact of the key switch can no longer meet the demand of large current. It can easily cause the contact to burn out.

Let's take a look at the appearance of the electromagnetic power supply main switch:

This is mainly used to replace the manual power main switch. Many models such as trucks, agricultural vehicles, engineering vehicles and so on will be equipped with mechanical power switch, also called "gate", the purpose is to disconnect the main circuit, to prevent battery loss. But manual use is more troublesome, far less convenient than electric switch, long life, low mechanical failure. Let's look inside the main power switch:

It can be seen that the structure is slightly different from the starting relay, and it is somewhat detailed from the magnetic switch of the starter. This switch has high working current and strong magnetic force, adopts sterling silver contacts, and has higher reliability and longer life. At the same time the cost is high, so is the price. Armature has a moving contact, similar to the principle of AC contactor. The magnetic force generated by the coil absorbs and holds the armature, and then the two static contacts are connected by moving the contacts.
It can be seen that the wiring method is the same as that of ordinary relays, except that the contact capacity is larger, the magnetic suction is also strong, and the infrequent action is more reliable. Circuit directly to the battery line off, almost all the car's current through the electromagnetic switch. When the key is turned on, the control coil on the main power switch is powered, the electromagnetic switch draws the internal contact and connects, and the vehicle recovers power supply.
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