making the solenoid
Energy-saving production methods electromagnet

Electromagnet pull the moment, you need a larger current, and in the pull after the retention period, requiring only a small holding current. This feature combined with the electromagnet, the author developed a pull, hold function dual coil solenoid control circuit as shown in drawings.
Circuit, D1 for the rectifier diode, D2, D3 is the freewheeling diode. U1 is BT33, triggered by the single-junction transistor, R1 limiting resistor and so on. L1 is the holding coil, wire wound with φ0.2mm, DC resistance 290Ω; L2 coil is energized with Φ0.51mm enameled wire, DC resistance 19Ω. U1 and R1 together form the suction coil control drum separator circuit, C1, V4, N2 delay control circuit, and the like.

By the AC_A and AC_C input voltage 380V AC, half-wave rectified by D1 and R1 after limiting power supply for the control system. After the system is energized to keep the coil L1 is energized for a while by R1 and R2 E1 charging. In the initial period of energization, C1 voltage is less than 1.5V, the transistor N2 is off, R5, C2, and a thyristor trigger circuit U1 is configured to work, so that thyristor T1 is turned on, pull coil L2 is working. After about 0.4s, C1 rises above the voltage of 1.5V, the transistor N2 is turned on, the base voltage U1 is lower than the operating voltage, the SCR trigger circuit is stopped, T1 is disconnected, L2 and stop working because of loss of power . The power within the first 0.4s, L1, L2 simultaneously, suction force max. Thereafter, only the L1 work, maintain system pull.Drawer magnets  Changes in the value of R5 and C2, L2 adjustable operating current.

Suction force applied to the control circuit of the electromagnet is 30kg, suction timely powerful, while maintaining state can maintain sufficient suction force. I use a magnetic core by 18mm, core length 20cm, here provided only a design approach.