Product category:
Electrical and Electronic Components
News Release from: Carlo Gavazzi | Subject: DTA01 and DTA02
Edited by the Engineeringtalk Editorial
Team on 17 September 2004
Relays protect against thermal damage
New temperature monitoring relays allow multiple sensor arrays to be positioned optimally to protect against thermal damage regardless of the cause.
New temperature monitoring relays from Carlo Gavazzi designed for use with PTC thermistor sensors allow multiple sensor arrays to be positioned optimally to protect against thermal damage regardless of the cause The DTA01 and DTA02 are 22.5mm DIN-rail mounting relays suitable for thermal protection of three-phase electric motors and generators, and other wound components such as transformers, actuator coils and solenoids, electromagnets, or induction regulators
This article was originally published on Engineeringtalk on 1 Mar 2001 at 8.00am (UK)
Related stories
Neat electronic alarm warns of water leaks
Waterstop is a new electronic alarm system which provides an early warning of water leaks; it fits on to the wall at ground level and can be hidden completely behind the wall panel
Plastic bodies cut price of photo sensors
Carlo Gavazzi has launched a new range of photo sensors in M18 housings, significantly lower in price thanks to the use of rugged plastic bodies rather than metal
The DTA02 also provides remote and local alarm reset capabilities, a test button, and LED indication for relay and power supply on.
Two further new relays, the PTA01 and PTA02, have the same functionality and ratings as the DTA01 and DTA02, respectively, but are delivered as 36mm plug-in modules.
The relays operate with PTC thermistors located at the precise point where protection is needed, such as in the stator windings of a three-phase motor.
The protection temperature is configured to fall within the highly non-linear part of the thermistor characteristic, causing a sharp increase in sensor resistance for a small increase in temperature.
This large delta causes the relay to act, shutting down the protected equipment.
The relay responds on detection of an increase from -20% to +20% of the preset value, acting within 150ms to shut down the protected device.
Combining the relay with a PTC sensor protects against heat damage regardless of the cause.
In a motor application, this may be due to equipment failure, such as a locked rotor, running overload, voltage imbalance or single-phasing, or due to an external fault such as inadequate ventilation or excessive ambient temperature.
Multiple PTC sensors can be used if redundancy is required.
Because the protection temperature is fixed by sensor selection, no preliminary setting is required.
Tampering by unauthorised personnel at the customer site is also impossible.
Further features include PTC short circuit detection, and a latch function to allow manual re-start of the motor in case of failure.
The DTA01-PTA01 and DTA02-PTA02 temperature monitoring relays extend the Carlo Gavazzi range of monitoring relays to cover all the most important electrical values including current, three-phase voltage, power and frequency, with a wide choice of features to suit virtually any application requirement.
• Carlo Gavazzi: contact details and other news
• Email this article to a colleague
• Register for the free Engineeringtalk email newsletter
• Engineeringtalk Home Page
