How does the BK transformer protect the machine tool circuit after a sudden power outage?

1. Physical isolation and voltage stability

(1) Isolation of high and low voltage circuits
The BK transformer adopts a dual-winding isolation design. In the event of a sudden power outage, even if the grid voltage instantly returns to zero or fluctuates, the physical isolation can block the interference of abnormal signals on the high-voltage side to the low-voltage control circuit of the machine tool.

(2) Voltage stabilization and filtering function
The BK series has a built-in low-loss silicon steel core and an anti-harmonic winding structure. When the grid voltage fluctuates for a short time (such as instant power outage recovery), the output voltage mutation is suppressed through the hysteresis effect of the core, and the secondary side voltage change rate is controlled within 1~1.5%.

2. Overcurrent protection and load safety

(1) Instantaneous overload capacity
The BK transformer is allowed to last for 1 minute at 2 times the rated current. At the moment of power outage recovery, it can withstand the instantaneous starting current of machine tool motors, solenoid valves and other equipment to avoid winding burnout due to overload.

(2) Current limiting and fuse linkage
When power is restored after a power outage, if there is a short circuit fault in the machine tool circuit, the BK transformer limits the output current through the overcurrent protection function, and cooperates with the fuse in the control cabinet (such as FU1, FU2) to quickly cut off the fault circuit.

3. Zero voltage protection and self-recovery control

(1) Zero voltage protection circuit
In the event of a sudden power outage, the secondary output of the BK transformer returns to zero, triggering the zero voltage protection relay of the machine tool control system to lose power, cut off the contactor coil circuit, and force all actuators to stop running. After the power supply is restored, the start button must be manually pressed to reactivate the circuit to avoid personal injury or mechanical collision caused by accidental startup of the equipment (refer to the zero voltage protection logic in).

(2) Delayed restart mechanism
Some high-end BK models have a built-in power-off delay relay module, which can preset the restart delay time (such as 5 to 30 seconds) to ensure that the power supply is restored after the grid voltage is stable, and prevent frequent start-stop impact on the circuit.

4. Collaborative protection with machine tool control system

(1) Gravity axis brake support
On machine tools equipped with gravity axes, the BK transformer provides a stable low-voltage power supply for the brake control circuit. In the event of a sudden power outage, the primary voltage drop signal is detected to trigger the built-in circuit of the amplifier to instantly activate the brake to prevent the gravity axis from sliding down due to power failure and damaging the workpiece or tool.

(2) Data cache power maintenance
The BK transformer can extend the uninterruptible power supply interface to provide millisecond-level power support for the data cache module of the CNC system at the moment of power outage, ensuring that key data such as machining programs and coordinate parameters are not lost.

5. Surge and lightning protection design

(1) Surge absorption and grounding protection
The secondary output end of the BK transformer uses a metal oxide varistor to absorb transient overvoltages, and at the same time, the residual current is directed into the ground through reliable grounding (grounding resistance ≤ 4Ω).

(2) Insulation and voltage resistance enhancement
The transformer winding adopts H-class insulation material and vacuum varnishing process, with insulation strength of 2000V/1 minute without breakdown. Even if there is a sudden power outage and then power on in a humid environment, it can resist the risk of insulation breakdown.