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Operating 50 Hz motor on 60 Hz using VFD
- Thread starter Junaid16
- Start date
A useful trick - with a suitable motor - is to reconfigure the motor from star connection to delta connection then use it with a drive configured to reach full voltage at [√]3x the motor base frequency, e.g. to run a 50Hz motor at 86Hz. This maintains the volt/Hz ratio up to the higher frequency and effectively gives a [√]3 increase in power output because of the higher shaft speed while achieving rated torque.
mikekilroy
Electrical
iop95 (Electrical)12 Oct 15 09:30
120% speed the PUMP will require 172% power, but if suppose motor torque is equal with PUMP required torque at rated, motor can't supply a higer torque than rated (suppose can increase voltage at 60Hz accordingly), so PUMP speed can't increase and don't require 172% power. At 60Hz, motor torque curve may intersect PUMP curve in unstable zone.
iop95 (Electrical)12 Oct 15 12:47
waross, it's true if motor have enough torque to accelerate pump at that speed, so will be in overload, but if don't have torque will go in unstable region
iop, you have mentioned 'unstable region' & 'unstable zone' many times. I have never heard of this. Would you please explain what & where this is?
120% speed the PUMP will require 172% power, but if suppose motor torque is equal with PUMP required torque at rated, motor can't supply a higer torque than rated (suppose can increase voltage at 60Hz accordingly), so PUMP speed can't increase and don't require 172% power. At 60Hz, motor torque curve may intersect PUMP curve in unstable zone.
iop95 (Electrical)12 Oct 15 12:47
waross, it's true if motor have enough torque to accelerate pump at that speed, so will be in overload, but if don't have torque will go in unstable region
iop, you have mentioned 'unstable region' & 'unstable zone' many times. I have never heard of this. Would you please explain what & where this is?
I'm not sure why you call that an unstable zone, but typically, per the Cowern Papers, maximum torque is at about 80% of sync speed.
1500 RPM is 83% of 1800 RPM, still above maximum torque.
The original question:
The question as it seems to be developed;
Can we run 50 Hz driving a centrifugal pump at 60 Hz.
Only if the motor is about 75% over sized at 50 Hz.
Bill
--------------------
"Why not the best?"
Jimmy Carter
1500 RPM is 83% of 1800 RPM, still above maximum torque.
The original question:
Simple Answer; YES.The Original Question said:
The question as it seems to be developed;
Can we run 50 Hz driving a centrifugal pump at 60 Hz.
Only if the motor is about 75% over sized at 50 Hz.
Bill
--------------------
"Why not the best?"
Jimmy Carter
Is an unstable region related to load curve (as operating point or band); a small torque change lead to a high speed change.
mikekilroy
Electrical
iop95, that terminology must be new term they are teaching kids today as I never heard it used in EE school back in mid 19070's until now. Thanks for sharing.
No, it's not new...but maybe not often used.
I have heard first time in school, 25 years ago.
I have heard first time in school, 25 years ago.
mikekilroy
Electrical
HA! Proves my point - new. 25 years ago is new compared to 40 years ago
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