Motor Dynamic loads

Worst case scenario for a motor is when a running motor abruptly stalls.

Locked rotor current for design assessments is taken as six times the rated name plate value, this evaluation will give you the transverse force on the foundation bolts to go ahead with further resolution.

Would you please eleborate a bit. I am a Mechanical Engg..did not understand 'Locked rotor current'. How it is related to dynamic loads?

I didn't understand that either. More important IMHO is the maximum torque, typically 2 x rated torque at start-up, which the motor mountings and support structure must be able to take. But I doubt whether this is often allowed for specifically, if the mounting bolts are the right size for the holes you won't go far wrong.

For dynamic load when running at full speed, again I doubt whether anybody normally worries about it being significantly above the motor weight. The driven equipment might be different, but that wasn't asked.

Cheers......Codey

I am too under the impression that dyanamic loads wont be higher than motor weight itself. But sometimes when we have a high voltage motors like upto 6MW motors, the dynamic loads cannotbe neglected.

I am looking to calculate these dymanic loads ...

A standard curve for a squirrel cage (SC) motor provides locked rotor torque to be 1.5 times, breakdown torque to be 2.5 times and pull-up torque at starting nearly 1.25 times the full load torque.

For small motors it is usual to neglect the dynamic component in consideration of driven equipment but motors tend to be larger ( say 3200000 hp!).

I don't understand the 2nd paragraph, please explain. And have you ever seen a 2.5 MW motor? I'm not sure what the biggest power station generators (steam turbine driven) produce, but I'd expect 2.5 MW to be good going.

Cheers.........Codey

I have come across motors upto 6 MW...for these if we try and calculate the dynamic loads..the value which we would arrive at cannot be negleted...

Sorry guys, I should of course have said 2500 MW (approx 3.2 million hp)

Unless they've grown in the last few years, 1000 MW is a big power station generator.

Cheers.........Codey