What an electrosurgical output stage demands
A high-frequency electrosurgical unit (ESU) replaces the mechanical scalpel: high-frequency, high-voltage current from an active electrode heats tissue at the tip to cut and coagulate, achieving dissection and hemostasis. Producing that waveform means combining high voltage, high current and a relatively high operating frequency in one output stage, which in turn raises the shock risk to patient and staff and makes the isolation of every switch in the path a safety parameter rather than a convenience.
HVR series figures
The HVR high-voltage reed relay is offered in 4/5/6/10/15/20 kV withstand versions.
- Contact switching voltage to 10 kVDC
- Dielectric (breakdown) withstand to 20 kV
- 3 A switching current; 5 A maximum carrying current
- Pulse current options 5 A / 10 A / 20 A
- Insulation resistance 10 TΩ and above
- Multiple contact forms; PCB through-hole or high-voltage lead-wire mounting
- Operate time 3 ms, release time 1.5 ms
Integrating the relay into the output stage
The ESU output is a difficult place for a switch because kilovolts, amperes and an RF waveform arrive together. The HVR’s contact configurations and two mounting styles cover both board-level and point-to-point HV layouts, and the 3 ms operate / 1.5 ms release times let the control electronics gate cutting and coagulation energy promptly. The body is epoxy-encapsulated, with insulation resistance of 1012 Ω and a creepage distance greater than 32 mm — the physical margins that keep the RF output from finding an unintended path in a patient-connected device.
Isolation is the safety requirement
The core rule in electrosurgery is that the high-frequency energy reaches the target tissue and nowhere else. A switch in the output path that cannot hold off the output voltage, or that arcs or leaks internally, can route dangerous current to the patient or to anyone touching the equipment. That is the reason to specify dielectric withstand to 20 kV, 1012 Ω insulation and more than 32 mm of creepage: these are the margins that contain the RF energy, and the 3 ms / 1.5 ms timing lets the controller remove energy quickly when the surgeon lifts the electrode or a fault trips.
Same platform in defibrillators
The same high-voltage relay platform is used in cardiac defibrillators, where the switch must hold the kilovolt-level capacitor charge and close reliably on demand. The combination of up to 20 kV withstand, sealed contacts and epoxy encapsulation carries over directly; in both cases the relay is specified against the worst-case stored energy, not the nominal operating voltage.
About SHR AUTOSENSOR
SHR AUTOSENSOR TECH LIMITED (SHR AUTOSENSOR) manufactures high-voltage reed relays, mercury wetted relays and high-voltage DC contactors. Contact: [email protected] | +86 13761571029 | www.reed-relay.com