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I concur with aolalde response. - V/f ratio should remain the same while changing frequency - Rated HP should be decreased. The thread edison123 is refering was posted by me and i gave practical values myself at the end. Unfortunately my memory is the same as edison123 (no offence edison123)...

Two Nameplates (50HP & 40HP) A motor when it is being used with a VFD has to be an inverter duty motor. If, for some reason, the manufacturer has zero stock, motors of a higher rating are used (i.e. 50HP instead of 40HP) but this is only a temporary solution. These higher rating motors are not...

Jarvis, always remember that it is always less severe for a motor to be running continously rather than on an on/off cycle, no matter what the on/off cycle might be.

Well electricpete, that sure beats me too except that i have seen that happening. Maybe when you use sealed bearings, the presurized water has nowhere to go except between the clearances between the bearings and the end shields of the motor. The sealed bearings might add up to the pressure...

Any seal designed for IP55 degree of protection would work. It would be better to go back to the manufacturer and ask them for a field conversion set of these seals. Using sealed bearings would cause the water to go into the windings rather than onto the bearings like they have been doing upto...

Couple of points on jbartos reply: ///Duty Cycle: At most, the machine operates for a few hours at a time, but the motor would see it as bursts of 5-7 minutes, break for a couple, another burst, and so on, for about a 4 hour stretch. Does this count as "Continuous Duty"? /// By what i...

well this is too late for an answer, but maybe it might help. Using VFD's you can control the speed of the motor and hence the flow of the pump. The advantage lies in the fact that power decreases by the cube of the speed decrease. Thus a 5% (0.95) speed decrease will cause the power requirement...

Well i guess that the torque would not be fully transmitted from the driving machine to the driven machine due to shaft misalignment. Furthermore the motor will draw a higher current and will eventually burn out. The burn out time will depend on the degree of misalignment.

You are experiencing difficulties because differention and integration are not meant to be used in disrete quantities. They are operations that are used in continous quantities.

To electricuwe Thanx for the tip. I was measuring it in terms of industrial acceptance. kassad

In my experience you can use standard motors with inverters. But you have to be carefull to select a higher rating than your load. eg with a load of 10 HP you can use a 15HP motor. But this only works if the speed variation is not greater than 50%. Using a standard motor with inverters will...

well rgmaxwell the motor is undersized. A service factor of 1.15 means that the motor can be overloaded to 115% more than the rated HP. For a peak demand of 9.9KW you need to use a 15 HP (11 KW) motor. A motor smaller than 11 KW would be 7.5 KW and with a service factor of 1.15 the max...