doubt regarding GD2 of motor

What in the world does anything involving tumors (GD2) have to do with motors and pumps? Please define your acronym.

Google has far too many links which can help you..... remember, 'God helps those who help themselves'....(There was an exception though. A bank cashier followed this, and regrettably, ended up at Sing Sing )

_{To describe the moment of inertia, J and GD² is used. J is generally called inertia and has the same value of physical moment of inertia in SI units. Unit is in kg·m².
GD² (GD squared) is called "flywheel effect" and generally used in industrial application with gravitational systems of units. Unit is in kgf·m² or kgf·cm². A relation between J and GD² is described as:}

_{J = GD² / 4}

Here is one example : GDsquared

It is not so. Surprisingly, in many cases, the reverse is true (i.e.) GD2 of the driven equipment will be more than the GD2 of the motor.

Actually I am facing the same case in which (PUMP + COUPLING)GD2 is more than MOTOR GD2 but i am unable to understand the exact reason behind it. THe only thing that i Have understood is that we want starting time of induction motor to be less than thermal withstand time and i am assuming this to be the reason behind it.Can u please explain the reason for (PUMP + COUPLING)GD2 to be more than MOTOR GD2???/

Quite right too. Is this not why the IEC classifies relays into 4 grades (Class 10,20,30 and 40) depending on starting time ? High-inertia, long-start applications. Maybe fully laden conveyor belts for example...

KVS ! Pl. clarify! Vide Clause 4.7.3 (2) of IEC 60947-4, the trip classes for overload relays are Class 10A, 10, 20 & 30. Is Class 40 included in any latest revision?

Dear Mr.electricalexpert65,

If the GD^2 of the driven equipment will be more than the GD2 of the motor.-, starting of the equipment will be a serious Issue/problem, one such experience I faced - for an equipment called FIBRISOR in a Cane Sugar Plant, driven by 2000 H.P., 11 KV Motor - which had 4% Slip and t The Fibrisor had swing hammers of 18 Kgs. each and the No.of Hammers were 120, total weight 2160 Kgs, Shaft Weight -2000 Kgs., Coupling Weight 650 Kgs.

The starting was not possible, and motor tripped. The problem was solved in starting the motor by 2 steps.

1. 40 Nos. of Hammers removed as a Temporary Measure, to reduce the GD^2 value.

2. A grid resistor was added to the Rotor circuit to develop more torque and increase the Slip of the Motor was increased to 15%

3. Then it was decided to replace the Grid Resistor with Auto-Slip Resistor to the Motor Rotor circuit, put back the hammers which have been removed.

Now it is working alright with 120 hammers, and Auto-Slip Resistor to the Moto.

DHAYANANDHAN.S

Dear Friend,

The motor GD^2 value MUST be more than the GD^2 of (PUMP + COUPLING). Then only the equipment will start and accelerate to full speed. Then only the starting Torque will be more than the Load Torque. The Higher the GD^2 of the Motor, the faster and quicker the starting and attain full speed and take the load.

If GD^2 value of motor is less then, the Motor will not start, start humming and the starting current will increase and get tripped. If it does not tripp, the motor or starter get damaged.

DHAYANANDHAN.S