VH overheat protection relay
The VH relay is intended to protect industrial electric equipment against harmful overheating.
Principle of operation:
PTC (positive thermo coefficient) thermistors are mounted into relevant parts of equipment to be protected (e.g. transformers, electric furnaces, welding, X-ray equipment etc.) In case of motors into each phase of the stator windings or in the bearing.
The resistance of the thermistors increases rocketing with many older of magnitude.
The outputs of the PTC are connected to VH relay.
At rated operating temperature the of relay’s contact breaks and turns-off the contactor of the protected equipment.
Alternative thermistors: from 70 °C to 150 °C with 10 °C „steps
The thermistors placed inside one equipment should be series connected.
The VH relay is resets automatically, but (after cooling or at returning of voltage) it should be turn-on the circuit of contactor by pushing of push-button ON.
Dimensions: 50×72×111 mm
Mounting: to 35 mm rail or 2 pcs M4 screws
Degree of protection: IP 20
Relevant standards: EN 60255-6, EN 61010