Table of Contents
What causes a thermal overload to trip?
Causes may include a large change in load (e.g., a scrap grinder is fed too much at a time), misalignment, a broken drive gear, or improper motor drive settings. Power problems (e.g., low voltage or low power factor) also may cause an overload condition.
Can thermal overloads be reset?
The bimetallic thermal overload relays have thermal memory. Once tripped, the relay will not reset until it has cooled down, allowing the motor to cool before it can be re-started.
What is the function of thermal overload?
Thermal overload relays are protective devices. They are designed to cut power if the motor draws too much current for an extended period of time. To accomplish this, thermal overload relays contain a normally closed (NC) relay.
How do electronic overload relays work?
The overload relay is wired in series with the motor, so the current that flows to the motor when the motor is operating also flows through the overload relay. It will trip at a certain level when there is excess current flowing through it. This causes the circuit between the motor and the power source to open.
How do you set thermal overload?
Thermal Overload Relay setting = 100% x Full Load Current (Line).
- Thermal Overload Relay setting = 100% x Full Load Current (Line).
- Thermal Overload Relay setting = 100%x6 = 6 Amp.
What is a thermal overload used for?
Thermal Overload is widely used for Motor Protection. Basically Thermal Overload Relay is an overcurrent protection of the simplest type. The working principle of Thermal Overload Relay is quite simple but interesting.
How does the thermal overload relay work?
A thermal overload relay works on the heat produced by the excessive overload current. The heat produced by the overload current is utilized to trip the motor circuit. Sep 11 2019
What is a thermal overload switch?
Schematic symbol for a thermal overload switch. A thermal switch (sometimes thermal reset or thermal cutout (TCO)) is a device which normally opens at a high temperature (often with a faint “plink” sound) and re-closes when the temperature drops.
What is thermal overload protection in motor?
A starter will contain protective devices for the motor. At a minimum this would include a thermal overload relay. The thermal overload is designed to open the starting circuit and thus cut the power to the motor in the event of the motor drawing too much current from the supply for an extended time.