Motor Design Characteristics
Motor Design Characteristics
(OP)
I need Help? I have a motor 440V,2.2KW, 60Hz, 3460rpm, 3.9A PF=0.74, 3 phase. It requires to be installed into a 415V 50Hz system is it possible and what will the above values change to? Please if possible show all workings out cos I am stuck Cheers!





RE: Motor Design Characteristics
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RE: Motor Design Characteristics
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RE: Motor Design Characteristics
"The perfect is the enemy of the good." -- Voltaire
RE: Motor Design Characteristics
RE: Motor Design Characteristics
Voltage 440V x 50Hz / 60Hz = 367V 416V/367V = 120%
Saturation is a possibility.
How old is the motor? 440V hasn't been a standard voltage for 40 or 50 years.
Bill
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"Why not the best?"
Jimmy Carter
RE: Motor Design Characteristics
RE: Motor Design Characteristics
RE: Motor Design Characteristics
RE: Motor Design Characteristics
If you plan to use the same pump, the pump output will drop drastically at 50 Hz. So you need to use V belts and pulleys to get it up to original speed. In which case, the motor will be undersized.
60 Hz to 50 Hz is a bitch, ain't it ?
RE: Motor Design Characteristics
My bad on the voltage. You will be 13% over voltage. Very close. Some motors will accept +113%, some will fry.
Are you sure the motor is not 460 Volts? That is the standard voltage.
Bill
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"Why not the best?"
Jimmy Carter
RE: Motor Design Characteristics
However, there will be a reduction in speed of the new motor from the 50Hz frequency, this must be a 2-pole motor, running with 4% slip, (slip will be slightly higher on the lower frequency) So new running speed will be around 2800 rpm, this will change the flow rate, probably lower it, it may also improve efficiency, this will determine the torque required from the motor. Historically, many motors were over-rated for the duty and so this may still be OK on 2.2KW, also, if the pump is old, then you will find the Q-H curve will be lower due to wear, approx 1% in head per year. The V/f ratio is important, but the consequence of increased v/f ratio (4.8 for new motor, 4.2 for the original) will be lower current. Note the other disadvantage of the lower speed will be lower airflow from the TEFC fan, this could be as much as 36% reduced cooling (1-(S1/S2)^2)
Having said all this, i suspect you wont have the Q/H curve and also required head will also be unknown.
So, my recommendation would be if this is the only available motor, you try it. Measure the current the pump draws and then work out the power drawn, if this is close to 2.0KW, then you are lucky, then all you need to do is check the temperature of the motor over extended running.
BUT.... the final question would be to ask about load factor. if this pump is for occasional use, then energy efficiency wont be important. But, if load factor is above 75%, then the best recommendation you can make to your boss is to buy a new high efficiency pump and motor, you will see payback in less than 12 months from improvement in energy efficiency. The rule of thumb is that for a continuously running pump, it consumes its own capital cost in energy in 1 month, we get far too posessive about our pumps and motors! Pennywise £ foolish!
RE: Motor Design Characteristics
Measuring the current will tell you how much current the motor draws, but not how much power it is delivering. You need to measure the poower factor too, and that's a little harder without specialist equipment. Power factor is load-dependant so the nameplate value is of limited use.
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