Here is a dilemma. The electrician in my village isn't so much internet savvy as I guess(and I am not electrical expert) so I am asking this question here on his behalf. It's just similar to another question asked on stack exchange, but as I am novice in electricity, I am attaching the images also

Problem : We have a motor with this specification which is in star delta configuration. When we start in star it's ampere reads around 4, and when in delta it goes up to 30 ampere and then mcb cuts the power after 6-10 seconds.

enter image description here

It is a 15 hp motor. In the below image is the panel . The lower part of the panel is for this motor.

Interestingly we have another motor in star delta configuration(upper part of panel) which works fine. It's of different hp.

PANEL : enter image description here

[![enter image description here][4]][4]

  • \$\begingroup\$ a) The nameplate shows 3.7kW, 415V delta motor, not 15HP. b) the used circuit breaker is not for the use with motor. You should use a motor protection breaker. \$\endgroup\$ – Marko Buršič Sep 4 '17 at 15:06

As Marko Buršič pointed out, the motor is rated 3.7 kW (5 Hp) not 15 Hp. Either the motor's power rating is not high enough for the load, or the transition from star to delta is being done too quickly. If the load is a fan or centrifugal pump, the load will be very low at first and then it will increase very quickly as the motor speed increases. The very low current in star seems to indicate that the motor can supply the initial starting torque, but, in delta, the motor very quickly accelerates the load to a speed where the motor can no longer supply enough torque for further acceleration. The motor draws a high current attempting to accelerate the motor to full speed, but it does not have enough torque.

With a weak (high impedance) power distribution system, the higher current may cause the voltage to drop if the transition is done too quickly. In that case also, the motor may not have enough torque due to lack of sufficient voltage.

There is also the possibility of a mechanical problem with the load, some problem with the motor or a wiring error.


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