Structure and Working Principle

Basic Structure

DHFZ(R)N‑40.5 Series Vacuum Load Switch mainly consists of frame, vacuum interrupter, isolating blade, fuse, earthing blade, trip transmission device and spring operating mechanism. The isolating blade and vacuum interrupter are fixed on the frame via insulators. The fuse is mounted on the rear side of the isolating blade. The main shaft of the earthing blade is directly fitted to the lower part of the frame. The spring operating mechanism is assembled on the side plate of the frame with side‑operation mode.

The operating mechanism drives the main shaft of the switch. The rotation of main shaft, together with crank arm and insulated operating pull‑rod, drives the vacuum interrupter or isolating blade to perform opening and closing operations. The earthing blade and isolating blade are connected by transmission connecting rods for interlocked operation with reliable mechanical interlock.

‑ For outline and installation dimensions of the combination device, refer to Figure 1 and Figure 2.

Working Principle

Operation of Vacuum Interrupter

The spring operating mechanism equipped for vacuum interrupter of DHFZ(R)N‑40.5 Series Vacuum Load Switch supports motor‑driven operation (see Figure 3 for control circuit wiring diagram).

For closing operation: The motor gearbox energizes and releases the closing spring to close the vacuum interrupter, meanwhile the opening spring of the switch is charged.

For opening operation: An opening pulse signal is sent to the opening solenoid. The solenoid actuates and strikes the opening trigger, the opening spring releases and completes the opening of vacuum interrupter.

Manual operation of spring operating mechanism is also available on operation panel: Rotate the operating handle 180° towards closing direction through the operating hole of load switch to realize manual closing of vacuum interrupter. Press the opening button on operation panel to open the vacuum interrupter.

Status indication of “OPEN” / “CLOSE” is shown at the status‑indication window of vacuum interrupter, whether at open or closed position.

1.Earthing shaft 2. Main tension spring 3. Main shaft 4. Isolating shaft 5. Frame 6. Isolating blade 7. Insulated pull rod 8. Upper support base 9. Vacuum interrupter 10. Insulator 11. Lower support base 12. Earthing blade(L=530 mm or L=330 mm)

1.Frame 2. Main tension spring 3. Main shaft 4. Isolating shaft 5. Fuse 6. Insulated pull rod 7. Upper support base 8. Vacuum interrupter 9. Insulator 10. Lower support base

Opening and Closing Operation of Isolating Blade and Earthing Blade

The vacuum interrupter, isolating blade and earthing blade of DHFZ(R)N‑40.5 series vacuum load switch are equipped with reliable mechanical interlock. The isolating blade and earthing blade can only be operated when the vacuum interrupter is in open position. The isolating blade and earthing blade operate in interlock.

For opening operation of isolating blade: Insert the operating handle into the operating hole of isolating blade and rotate it 90° towards opening direction to open the isolating blade. Continue rotating the handle 60° in opening direction, the earthing blade completes energy‑storage and closing. At this time, the status‑indication window of isolating blade shows “OPEN”.

For closing operation of isolating blade: Ensure the vacuum interrupter is at open position. Insert the operating handle into the isolating‑blade operating hole and rotate 60° towards closing direction to open the earthing blade. Keep rotating the handle 90° in closing direction to close the isolating blade. The status‑indication window of isolating blade shows “CLOSE”.

Fuse Trip‑by‑Striking Opening

The fuse trip device of DHFZ(R)N‑40.5 series vacuum load switch is three‑pole interlocked. The matched fuse shall be striker‑type fuse. The trip device is flexible and reliable; it can open the vacuum interrupter with medium‑class tripping energy of 1‑3 J (Joule).

For combination device in closed position, when short‑circuit current or overload current flows through the main circuit, the fuse‑link of any‑phase three‑phase fuses will melt. The striker actuates and strikes the mechanical latch device of combination device, so that the vacuum interrupter realizes reliable three‑pole fast opening under the force of opening spring.

JX: Output terminal block    DL: Change‑over contact    TQ: Opening coil    M: DC closing motor    DX: Power rectifier unit

Note: The above components are built‑in parts of vacuum load switch with motor‑driven operating mechanism.

Closing Motor | Open | Close | Closing Indication | Opening Indication

Note: Components inside the dotted‑line frame are built‑in parts of the vacuum load switch.