industrial electrecity In a motor control circuit the therma

industrial electrecity

In a motor control circuit, the thermal overload relay\'s rated current is 5 Amperes. How long does it take for the relay trips off, when the motor current is 15 Amperes?

Solution

The motor control circuit has the the thermal overload relays rated current 5 amp, according to the question. Now this means that if the current in the circuit is greater than the rated value or the critical value the, the relay trips off will be happened. This is happened as the fuse in the circuit will be heated enough to burn and the relay off process is happened.

letus take the time to relay off when the current in the circuit is the critical value (i.e, i=5 amp) is t1
and the time to relay off when the current in the circuit 15amp is t2

Thus, H1=H2
=> i1^2*R*t1=i2^2*R*t2

=>(t2/t1)=(i1/i2)^2

=>(t2/t1)=(5/15)^2

=>t2=(1/9)*t1

Thus, the time to relay off for 15 amp current in the circuit will be one nineth of the time to relayoff at the rated condition.