The principle of operation of thermal motor protection relays is based on temperature rise. Therefore the ambient temperature of the device affects the tripping specifications. … This is achieved with a compensation bimetal strip that makes the relative position of the trip mechanism independent of the temperature.
Which relay is used for motor protection?
We use a stalling relay to protect motors during starts, since a standard thermal relay has too much time delay. A stalling relay will allow the motor to draw normal starting currents (which are several times normal load current) for a short time, but will trip the motor for excessive time at high currents.
What are the function of protective relay?
The function of protective relaying is to cause the prompt removal from service of any element of a power system when it suffers a short circuit, or when it starts to operate in any abnormal manner that might cause damage or otherwise interfere with the effective operation of the rest of the system.
How do I know if my overload relay is bad?
Give the compressor a shake if the start relay isn’t plugged in. If you hear rattling on the inside of the start relay, it’s time to replace it. You may have a problem with the actual compressor if it’s not rattling and in good condition.
How do you know if a relay is defective?
Here’s How To Test a Relay
- Locate the relay you need to test. …
- The quickest and easiest way to test a relay is to swap it out with a known good replacement. …
- Grab a multimeter and set it to Ohms. …
- Leave the multimeter on ohms or continuity. …
- Energize the electromagnet coil with a 9-12V battery across the pins.
Which relay is used for reverse phase protection in motor?
The Model 153 Reverse Phase Relay is designed to continuously monitor phase rotation of 3-phase lines. This device should be used in applications where proper phase rotation is critical, such as fan motors, compressors, grinders, elevators, etc.
What are the types of protection relays?
Basic classification of protective relays includes:
- Electromagnetic Relays: Armature. Induction cup / induction disc.
- Static Relays: Analog input signals are processed by solid state devices.
- Digital / Numerical Relays: Uses programmable solid state devices based on digital signal processing.
What is the function of overcurrent relay?
Overcurrent Relay Purpose and Ratings. A relay that operates or picks up when it’s current exceeds a predetermined value (setting value) is called Overcurrent Relay. Overcurrent protection protects electrical power systems against excessive currents which are caused by short circuits, ground faults, etc.