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Motogard™
General Information
Motogard Over-Temperature Protection Systems
provide immediate overheating protection for: motors,
equipment enclosures, semiconductor heatsinks,
sleeve bearings, and other related machinery.
All Motogard systems fully conform to the NEC
requirements for integral motor thermal protection.
The temperature inside of the motor is monitored at
all times by using Positive Temperature Coefficient
(PTC) Thermistors embedded in or in contact with
the surface.
The
Motogard
Over-Temperature
System uses PTC Thermistors to indicate when
the equipment has exceeded the set temperature.
These Thermistors act as a switch, which when
reaching the pre-selected temperature will cause
the resistance to increase to virtually infinity. This
causes the controller to change the state of the
contacts. As the equipment cools the "switching
action" reverses and the controller will then change
the state of the contacts back indicating an "OK"
circumstance.
Phone: 248-435-0700 Toll Free: 800-635-0289 Fax: 248-435-8120 www.ametekfactoryautomation.com
Note: This device does not monitor the actual
temperature but protects against over-temperature
conditions.
Protection
THERMISTOR TEMPERATURE
On Motogard Series 115, 120, and 135 Relays
the Thermistors are placed in parallel allowing
independent monitoring of 3-6 points in the
equipment. On Series 150 Relays, the three
Thermistors are wired in series reacting as a
single switching point. Although there is a higher
resistance switching point on the Series 150, each
separate Thermistor will pass 3500 ohms on over-
temperature.
SWITCHING RESISTANCE
FACTORY AUTOMATION
SWITCHING
TEMPERATURE
®
2
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