Test For Inductor Motor :No-Load and Blocked Rotor Test - Electronic Circuits Projects Diagrams Free

shermaine · 20th March 2004, 02:40 PM

For No-Load Testing

Any one knows why the no-load current and power of the motor expressed as percentage of their full-load values is considerably higher than those of a transformer?

For Blocked Rotor Test

Can the starting current be reduced to an acceptable value in practice?

Pls advise.
Thanks.[/u]

Styx · 20th March 2004, 06:16 PM

2nd question:

use a bank of resistors that are shorted out at startup

shermaine · 25th March 2004, 08:08 AM

Any one knows why the no-load current and power of the motor expressed as percentage of their full-load values is considerably higher than those of a transformer?

Russlk · 25th March 2004, 12:26 PM

The friction and wind resistance losses of the motor is higher than the magnetic losses of the transformer. The motor also has magnetic losses, but small compared to the other losses.

shermaine · 27th March 2004, 02:48 PM

(1) How do we analysis a motor performance under load conditions?
(2) Can i say that if for a no-load speed control by varying supply frequency, the volatge will be reduced or increase according to the frequency.....Normally, what's the percentage of changes? Let say i got a motor at speed 50hz and voltage at 220Vspeed=1415 rpm. Then when i reduced the frequency to 10hz....the voltage becomes 72.6v and speed is 299rpm....How do i know the pecentage of drop?
Pls advise.Thanks.

Russlk · 27th March 2004, 10:03 PM

1. Use a prony brake for power output and ammeter, voltmeter for power input. See: http://www.physics.purdue.edu/demo/1K/pronybrake.html

2. I don't know about variable speed drives, but would expect RPM to be 283, not 299 RPM. Any voltage reduction would depend on how the voltage is generated. If it is an alternator, I would expect the voltage at 10 Hz to be 44 volts, everything being equal, but the voltage can be varied by the field current, so set it for what you want.

shermaine · 28th March 2004, 02:17 AM

Hello,

If the experiment that we did it is of the values i given to u.
Does it make any sense? What could be due to the error?
Pls advise.
Thanks.

Russlk · 28th March 2004, 03:06 AM

Not knowing the details of the experiment, I cannot answer.

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20th March 2004, 02:40 PM	#1
shermaine	Test For Inductor Motor :No-Load and Blocked Rotor Test For No-Load Testing Any one knows why the no-load current and power of the motor expressed as percentage of their full-load values is considerably higher than those of a transformer? For Blocked Rotor Test Can the starting current be reduced to an acceptable value in practice? Pls advise. Thanks.[/u]

20th March 2004, 06:16 PM	#2
Styx	2nd question: use a bank of resistors that are shorted out at startup

25th March 2004, 08:08 AM	#3
shermaine	Any one knows why the no-load current and power of the motor expressed as percentage of their full-load values is considerably higher than those of a transformer?

25th March 2004, 12:26 PM	#4
Russlk	The friction and wind resistance losses of the motor is higher than the magnetic losses of the transformer. The motor also has magnetic losses, but small compared to the other losses. __________________ see my website: www.geocities.com/russlk

27th March 2004, 02:48 PM	#5
shermaine	Induction Motors (1) How do we analysis a motor performance under load conditions? (2) Can i say that if for a no-load speed control by varying supply frequency, the volatge will be reduced or increase according to the frequency.....Normally, what's the percentage of changes? Let say i got a motor at speed 50hz and voltage at 220Vspeed=1415 rpm. Then when i reduced the frequency to 10hz....the voltage becomes 72.6v and speed is 299rpm....How do i know the pecentage of drop? Pls advise.Thanks.

27th March 2004, 10:03 PM	#6
Russlk	1. Use a prony brake for power output and ammeter, voltmeter for power input. See: http://www.physics.purdue.edu/demo/1K/pronybrake.html 2. I don't know about variable speed drives, but would expect RPM to be 283, not 299 RPM. Any voltage reduction would depend on how the voltage is generated. If it is an alternator, I would expect the voltage at 10 Hz to be 44 volts, everything being equal, but the voltage can be varied by the field current, so set it for what you want. __________________ see my website: www.geocities.com/russlk

28th March 2004, 02:17 AM	#7
shermaine	Hello, If the experiment that we did it is of the values i given to u. Does it make any sense? What could be due to the error? Pls advise. Thanks.

28th March 2004, 03:06 AM	#8
Russlk	Not knowing the details of the experiment, I cannot answer. __________________ see my website: www.geocities.com/russlk