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OT: Sunon SP100A 115V fan (0.26A) in a 240V unit


 

Converting a 120V unit (it's OK with 50Hz) to 240V. Problem is that the fan
is a 115V unit (p/n 1123XBT).

I initially thought of a resistor in series, but I'm thinking that would
dissipate a LOT of power (470R resistor with 120V across it would dissipate
30W).

I then considered maybe a capacitor in series but wasn't quite sure what
value I'd need - initial thoughts suggested about 6.8uF - does that sound
right and would it even work?

Other than replacing it with a DP200A-2123XBT.GN (the 220/240V version) does
anyone have any suggestions?

Thanks
Dave


 

Random thought, use the 120V mains winding on the transformer as an auto transformer just for the fan ?

Robin

Sent from my iPhone

On 15 Jan 2018, at 13:19, David C. Partridge <david.partridge@perdrix.co.uk> wrote:

Converting a 120V unit (it's OK with 50Hz) to 240V. Problem is that the fan
is a 115V unit (p/n 1123XBT).

I initially thought of a resistor in series, but I'm thinking that would
dissipate a LOT of power (470R resistor with 120V across it would dissipate
30W).

I then considered maybe a capacitor in series but wasn't quite sure what
value I'd need - initial thoughts suggested about 6.8uF - does that sound
right and would it even work?

Other than replacing it with a DP200A-2123XBT.GN (the 220/240V version) does
anyone have any suggestions?

Thanks
Dave




Adrian
 

Hi David,

Stupid question ...I'm assuming this is not a tapped transformer input so you just leave the fan across 1/2 the primary?

Other than that I would go for the replacement fan, from the little I've done fans seem to present a strange (and to some extent dynamic) load and a capacitive voltage divider may not be quite straightforward?

...and fans wear out anyway.....

Adrian


 

No can do :(

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Robin
Birch
Sent: 15 January 2018 13:23
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: Sunon SP100A 115V fan (0.26A) in a 240V unit

Random thought, use the 120V mains winding on the transformer as an auto
transformer just for the fan ?

Robin

Sent from my iPhone

On 15 Jan 2018, at 13:19, David C. Partridge
<david.partridge@perdrix.co.uk> wrote:

Converting a 120V unit (it's OK with 50Hz) to 240V. Problem is that
the fan is a 115V unit (p/n 1123XBT).

I initially thought of a resistor in series, but I'm thinking that
would dissipate a LOT of power (470R resistor with 120V across it
would dissipate 30W).

I then considered maybe a capacitor in series but wasn't quite sure
what value I'd need - initial thoughts suggested about 6.8uF - does
that sound right and would it even work?

Other than replacing it with a DP200A-2123XBT.GN (the 220/240V
version) does anyone have any suggestions?

Thanks
Dave




 

I gave in and ordered the fan ...

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Adrian
Sent: 15 January 2018 13:46
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: Sunon SP100A 115V fan (0.26A) in a 240V unit

Hi David,

Stupid question ...I'm assuming this is not a tapped transformer input so you just leave the fan across 1/2 the primary?

Other than that I would go for the replacement fan, from the little I've done fans seem to present a strange (and to some extent dynamic) load and a capacitive voltage divider may not be quite straightforward?

...and fans wear out anyway.....

Adrian


keantoken
 

I wanted to do the same thing to limit the power output of a transformer. The problem is for all the useful power limiting values of capacitance, transformer inductance resonates with it near the power frequency. This is due to the fact that both the inductance and capacitance were chosen to have an impedance margin with the load, and so will have similar reactance at the power frequency. As we know, when an inductor and capacitor have the same reactance, they become a resonator.

Furthermore, assuming you could control the resonance, there is another problem. Nonlinear saturation of the magnetic core leads to a motorboating condition where the tranformer primary jumps to twice the mains voltage with a square wave! it buzzes like mad!
Synchronous motors would probably have similar problems although it would be fun to try out. I don't know about other motor types like brushed AC motors. On Monday, January 15, 2018, 9:06:58 AM CST, David C. Partridge <david.partridge@perdrix.co.uk> wrote:

I gave in and ordered the fan ...

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Adrian
Sent: 15 January 2018 13:46
To: TekScopes@groups.io
Subject: Re: [TekScopes] OT: Sunon SP100A 115V fan (0.26A) in a 240V unit

Hi David,

Stupid question ...I'm assuming this is not a tapped transformer input so you just leave the fan across 1/2 the primary?

Other than that I would go for the replacement fan, from the little I've done fans seem to present a strange (and to some extent dynamic) load and a capacitive voltage divider may not be quite straightforward?

...and fans wear out anyway.....

Adrian


Ed Breya
 

It depends very much on the specific fan brand/model/design. I have often added R/C networks to drop fan speed and noise. Some fans work just fine, while others don't. When you drop enough voltage to get a good speed range with a reactive network, the fan doesn't have enough starting torque to go reliably, and when you trim it back up to start well, it hardly drops any running speed. I always mark and set aside the relatively few good ones for low-speed applications. Ed


keantoken
 

Hmm. So you have to use a series resistor, but you can reduce the wasted power of that resistor by adding a series capacitor. On Monday, January 15, 2018, 12:05:38 PM CST, Ed Breya via Groups.Io <edbreya=yahoo.com@groups.io> wrote:

It depends very much on the specific fan brand/model/design. I have often added R/C networks to drop fan speed and noise. Some fans work just fine, while others don't. When you drop enough voltage to get a good speed range with a reactive network, the fan doesn't have enough starting torque to go reliably, and when you trim it back up to start well, it hardly drops any running speed. I always mark and set aside the relatively few good ones for low-speed applications.  Ed


Ed Breya
 

The resistor is small (often zero), sometimes used for damping - most of the voltage drop is on the cap. I've also tried various capacitive dividers, where there's a shunt cap across the fan too, to neutralize some of the motor inductance. Ed


 

It will take a high voltage film capacitor and 6.8uF may be about
right but be very careful about using too much capacitance and
overdriving the fan. Previously I have only added a capacitor in
series to lower the speed of an AC fan.

So start with a low value of capacitance and measure the AC voltage
across the fan.

On Mon, 15 Jan 2018 13:19:17 -0000, you wrote:

Converting a 120V unit (it's OK with 50Hz) to 240V. Problem is that the fan
is a 115V unit (p/n 1123XBT).

I initially thought of a resistor in series, but I'm thinking that would
dissipate a LOT of power (470R resistor with 120V across it would dissipate
30W).

I then considered maybe a capacitor in series but wasn't quite sure what
value I'd need - initial thoughts suggested about 6.8uF - does that sound
right and would it even work?

Other than replacing it with a DP200A-2123XBT.GN (the 220/240V version) does
anyone have any suggestions?

Thanks
Dave


 

I have done it with shaded pole motors commonly used with small AC
fans without problems. The shaded pole motors have so much loss that
I do not think resonance is a problem.

On Mon, 15 Jan 2018 17:51:03 +0000 (UTC), you wrote:

I wanted to do the same thing to limit the power output of a transformer. The problem is for all the useful power limiting values of capacitance, transformer inductance resonates with it near the power frequency. This is due to the fact that both the inductance and capacitance were chosen to have an impedance margin with the load, and so will have similar reactance at the power frequency. As we know, when an inductor and capacitor have the same reactance, they become a resonator.

Furthermore, assuming you could control the resonance, there is another problem. Nonlinear saturation of the magnetic core leads to a motorboating condition where the tranformer primary jumps to twice the mains voltage with a square wave! it buzzes like mad!
Synchronous motors would probably have similar problems although it would be fun to try out. I don't know about other motor types like brushed AC motors. On Monday, January 15, 2018, 9:06:58 AM CST, David C. Partridge