Sage-Tips

What is rated thermal current in contactor?

The thermal current rating of a contactor is the maximum continuous current each contact can carry without adverse degradation because of joule heating. But a contactor has to break that current when its coil is de-energised. And the higher the supply voltage the more difficult that breaking is.

How are contactors rated?

Ratings. Contactors are rated by designed load current per contact (pole), maximum fault withstand current, duty cycle, design life expectancy, voltage, and coil voltage.

What is rated thermal current?

The maximum amount of electrical current that a transmission line or electrical facility can conduct over a specified time period before it sustains permanent damage by overheating or before it sags to the point that it violates public safety requirements.

What is conventional enclosed thermal current?

The conventional enclosed thermal current is the value of current stated by the manufacturer to be used for the temperature-rise tests of the equipment when mounted in a specified enclosure.

What is AC1 and AC3 rating of contactor?

The difference between AC1 and AC3 contactors is AC1 contactor is used for less inductive loads such as resistive loads (the power factor of the load is near about 1) but AC3 duty contactors are used for high inductive, squirrel cage motors which will be off during the motor is running condition.

What is meant by ITH?

ithadjective. Occurring at position i in a sequence.

What are DC contactors?

A DC contactor is an electrically controlled device designed to switch current on and off. DC contactors control current in DC circuits by closing and opening internal contacts. DC contactors control much lower voltages than AC circuits and offer the benefit of minimal arcing as the circuit opens and closes.

Why contactor is used?

A contactor is an electrical device which is used for switching an electrical circuit on or off. These contacts are in most cases normally open and provide operating power to the load when the contactor coil is energized. Contactors are most commonly used for controlling electric motors.

What is rated uninterrupted current?

The rated uninterrupted current is the maximum current handling capacity that the conductors can handle without damage or without the contacts fusing. The In is the maximum current for a period less than 3 hours.

What is the heat current equation?

Hence the heating effect produced by an electric current, I through a conductor of resistance, R for a time, t is given by H = I2Rt. This equation is called the Joule’s equation of electrical heating.

What is AC1 and AC2?

1)AC1– Non-inductive or slightly inductive rows. 2) AC2– Starting of slip-ring motors. 3) AC3– Starting of squirrel-cage motors and switching off only after the motor is up to speed. (

What does AC1 mean on contactors?

AC-1 – This category applies to all AC loads where the power factor is more than 0.95. AC-3 – This category applies to squirrel cage motors with breaking during normal running of the motor. On closing, the contactor makes the inrush current, which is about 5 to 7 times the rated full load current of the motor.

What is the meaning of rated current of AC1 contactor?

It means the rated current of this contactor which can switch for thermal Load category AC1 is = Ith. Contactors have two currents values, One is current for thermal loads which are loads that transfer electrical current into thermal energy. i.e all types of heaters. The other current value is for other loads like motors.

What is thermal current rating (ITH) for contactors?

Electrical thermal current rating (Ith) for contactors What is thermal current rating (Ith) for contactors? It means the rated current of this contactor which can switch for thermal Load category AC1 is = Ith.

What is rated making capacity of a contactor?

Contactor’s rated making capacity is the value of current, on which the contacts of contactor can make the connections (i.e. Contactor can close their contacts) without arcing or melting. A.C contactor’s making capacity is defined according to the Current Symmetrical Component’s R.M.S value.

What is the thermal current of a 9 AMP contactor?

A contactor with 9 Amp. on AC3, And its thermal current (Ith = 20 to 25 A) (this means it can switch up to 20 or 25 A for loads of AC1 (thermal load). N.B: Contactor thermal current Ith is greater than I of loads with AC3 category. Our electrical engineer prepared amazing 10 levels electrical quiz, Just click the image below to take this quiz now