The composition of the power relay and its control function 4

If a short-circuit copper sleeve (or short-circuit coil) is placed between the coil and the iron core of the electromagnetic voltage power relay, the armature can not be pulled in or released immediately after the coil receives a signal or the signal disappears, and it takes a certain period of time. action. This kind of power relay is called electromagnetic time power relay, and its structure principle and symbol are shown in Figure 1-6a and b. This kind of component is essential in situations where delayed action or work in a certain time sequence is required. For example, in Figure 1-4, although the power supply voltage exceeds the user's specified value, it can return to normal in a very short time. At this time, it is not necessary to cut off the circuit to ensure the normal use of electricity by the user. For this purpose, a time power relay can be used to control, as shown in Figure 1-6c.

Under normal circumstances, the time power relay JS is connected to the control circuit power supply through the normally closed contact J2 of the voltage power relay, and its contact JS is closed. When the voltage of the power supply equipment exceeds the specified value, J will act, and J1 and J2 will be disconnected at the same time. However, due to the delayed release of the contact JS, the contactor O will remain closed for a certain period of time, so that the user will not be powered off. If the voltage returns to normal during this time, J is released, J1 is closed, and O will not be released naturally. If the voltage does not return to normal within the specified time, J1 and J2 are always disconnected, and the JS contact has been opened at the same time, so C is powered off and the user circuit is cut off. By adjusting the thickness of the non-magnetic gasket and the tightness of the return spring, the delay time can be adjusted within a certain range to meet the different needs of users for the delay time. However, the delay range of this kind of time power relay is small, the maximum is less than ten seconds, so when long-delay control is required, other types of time power relays need to be used (see appendix).