Mike Dolt Enterprises
Mike Dolt Enterprises
User: sgunsel, Location: Ann Arbor, Michigan
Asked on: Thursday, April 28, 2011 at 4:45 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:45 am EDT
Question: I normally deal with ac motors, but customer wants to use a DC motor. Where can I get an external thermal overload for a 0.5 HP, 24 VDC, 20 FLA, SF:1, continuous duty, motor?The motor does not have internal thermal protection. I don't know what the power source will be (solar, batteries, or ?).Thanks.
Thermal Overload for DC MotorsOption 1: Contact the Motor Manufacturer The motor manufacturer may offer external thermal overloads as accessories or compatible parts.
Option 2: Search for Circuit Protectors Circuit Breakers
Look for DC circuit breakers with a suitable current rating (20 FLA).
Example
Eaton Bussmann ANL-20 (20-amp DC low-profile circuit breaker)
Fuses
You may need to use a fuse holder and fuse with a suitable current rating.
Example
Littlefuse 9230019 (20-amp DC fuse)
Thermal Cutoffs
These resettable devices cut off power when overheating occurs.
Example
Littlefuse ATC Automotive Thermal Cutoff (compatible with 24 VDC)
Option 3: Consider a Custom Solution If no suitable commercial options are available, you can consider designing and implementing a custom thermal protection circuit using a temperature sensor, comparator, and relay.
Additional Considerations
Power Source
The thermal overload device should be compatible with the power source voltage and current.
Service Factor (SF)
Choose a device with a service factor equal to or greater than the motor's service factor to prevent nuisance tripping.
Installation
Follow the manufacturer's instructions carefully for proper installation and calibration.
Note: Some DC motors have built-in thermal protection features that may eliminate the need for an external overload. Flag for review