reduce the speed of a single phase induction motor

Hi Comrades, please what is the simplest way to reduce the speed of a single phase induction motor to about 50%?
also can a universal motor run for 24 hours on 90% load? (with all name plate ratings observed)
thank you.

 

[Phil Allison]

fynn...@gmail.com wrote:

----------------------------

Hi Comrades, please what is the simplest way to reduce the speed
of a single phase induction motor to about 50%?

** Just feed it with 25 or 30 Hz sine wave at about half voltage.

Or if that is a problem, use a gear or belt reduction system.

also can a universal motor run for 24 hours on 90% load?

** 24hrs, no problem.

But after that it is totally buggered.


..... Phil

 

[pfjw@aol.com]

On Monday, October 7, 2019 at 7:04:48 PM UTC-4, fynn...@gmail.com wrote:

Hi Comrades, please what is the simplest way to reduce the speed of a single phase induction motor to about 50%?
also can a universal motor run for 24 hours on 90% load? (with all name plate ratings observed)
thank you.

What we would need is horsepower, operating voltage, then anticipated maximum load.

https://cdn.automationdirect.com/images/products/large/l_gs110p5.jpg

These exist, but as the load increases, so does the cost.

As to operational capacities, if the motor is rated as "continuous" and properly cooled, there should be no issue about how long it runs as long as it is within its design load. NOTE: "Design Load" is generally some amount less than "Maximum Load". But not too much, typically around 10% - so you need to know which "90%" you are measuring.

https://www.plantengineering.com/articles/keeping-it-simple-steps-to-determine-motors-actual-load/

Gives you more on the subject.

Peter Wieck
Melrose Park, PA

 

On Mon, 7 Oct 2019 16:04:45 -0700 (PDT), fynnashba@gmail.com wrote:

Hi Comrades, please what is the simplest way to reduce the speed of a single phase induction motor to about 50%?
also can a universal motor run for 24 hours on 90% load? (with all name plate ratings observed)
thank you.

It depends on what type of single phase induction motor. The
typical single phase motor that you see powering bench grinders and
the like will often have a centrifugal starting switch, a potential
relay, or an electronic switch that controls the starting winding.
These cannot be made to run at 1/2 speed without extensive
modification and a power supply that provides AC at 1/2 the frequency
the motor is rated for. Other common motor types may not have any type
of switch and instead use a capacitor permanently connected to one
winding to shift the phase. These motors would also need the 1/2
frequency.
The reason for the 1/2 frequency is that the speed of most
induction motors depends on frequency. If the voltage is lowered the
motor will start to slow and will then consume more current in an
effort to speed back up to normal operating speed. If the voltage gets
too low the motor will just stall and then will overheat and
eventually burn up if the power supply can deliver enough current.
This stalling will happen way before the motor drops to 1/2 speed.
Shaded pole induction motors are controllable to some extent by
lowering the voltage. These motors are not very efficient. They are
mostly used for applications requiring little torque, like the
turntable in a microwave oven.
Shaded pole motors are sometimes used for fans and controls for
these can be bought at any store that sells home improvement stuff.
Shaded pole motors have a tiny starting torque and so are not
practical for anything other than starting very light loads, such as
fans and turntables. Their speed regulation is also poor as it is
quite sensitive to load changes.
Unfortunately there is no simple way to lower by 1/2 the speed of a
typical single phase induction motor.
Eric

 

[Trevor Wilson]

On 8/10/2019 10:04 am, fynnashba@gmail.com wrote:

Hi Comrades, please what is the simplest way to reduce the speed of a single phase induction motor to about 50%?
also can a universal motor run for 24 hours on 90% load? (with all name plate ratings observed)
thank you.

**This may be of some use:

http://www.siliconchip.com.au/Issue/2012/April/1.5kW+Induction+Motor+Speed+Controller%2C+Pt.1?res=nonflash

Appropriate alterations to suit your local mains supply will be required
of course.

--
Trevor Wilson
www.rageaudio.com.au

--
This email has been checked for viruses by Avast antivirus software.
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On Tuesday, 8 October 2019 00:04:48 UTC+1, fynn...@gmail.com wrote:

> Hi Comrades, please what is the simplest way to reduce the speed of a single phase induction motor to about 50%?

As folk have said, that's not a simple thing. There are various ways but all have issues, in some case the issue is just cost/complexity.

also can a universal motor run for 24 hours on 90% load? (with all name plate ratings observed)
thank you.

if it's rated to run continuously at 90% or greater load, yes. Otherwise no.


NT

 

On Wednesday, October 9, 2019 at 4:50:06 PM UTC+1, tabb...@gmail.com wrote:

On Tuesday, 8 October 2019 00:04:48 UTC+1, fynn...@gmail.com wrote:

Hi Comrades, please what is the simplest way to reduce the speed of a single phase induction motor to about 50%?

As folk have said, that's not a simple thing. There are various ways but all have issues, in some case the issue is just cost/complexity.


also can a universal motor run for 24 hours on 90% load? (with all name plate ratings observed)
thank you.

if it's rated to run continuously at 90% or greater load, yes. Otherwise no.


NT

Thanks to you all. you ve all given me a great deal of knowledge.