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DCV Control of PWM Fans
http://forums.swiftech.org/viewtopic.php?f=22&t=3347
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Author:  JackNaylorPE [ September 15th, 2015, 2:18 pm ]
Post subject:  DCV Control of PWM Fans

I have used your PWM page for reference dozens of times stating that DCV MoBo headers pr PWM => DCV modulation PCBs / controllers should not be used on 4 pin PWM fans. The answer I sometimes get in this regard is that they agree that it wouldn't be a good idea to control a Swiftech PWM pump but that PWM fans are just fine (despite Nidec's statement).

The statement on your PWM page says that minor voltage variations are OK, which I read as meaning **minor variations** .... as what's allowed under the ATX spec for the 12v rail (11.4 - 12.6 volts). I don't see 5 volts as a minor (58%) variation. The assumption is that MoBo manufacturers wouldn't allow the voltage to go \low enough to damage the fan and that PWM fan manufacturers say this is OK. So, the question is am I being overly concerned here ?

As a maker / seller of PWM fans in addition to PWM pumps, was hoping you could clarify your page a bit. Obviously putting a 4 pin PWM fan on a 3 pin / 4 pin DCV header loses low speed usability advantage but do we really need to worry about motor damage as Nidec describes within the warranty period of the fan ?

Author:  Bryan [ September 15th, 2015, 3:47 pm ]
Post subject:  Re: DCV Control of PWM Fans

JackNaylorPE wrote:
I have used your PWM page for reference dozens of times stating that DCV MoBo headers pr PWM => DCV modulation PCBs / controllers should not be used on 4 pin PWM fans. The answer I sometimes get in this regard is that they agree that it wouldn't be a good idea to control a Swiftech PWM pump but that PWM fans are just fine (despite Nidec's statement).

The statement on your PWM page says that minor voltage variations are OK, which I read as meaning **minor variations** .... as what's allowed under the ATX spec for the 12v rail (11.4 - 12.6 volts). I don't see 5 volts as a minor (58%) variation. The assumption is that MoBo manufacturers wouldn't allow the voltage to go \low enough to damage the fan and that PWM fan manufacturers say this is OK. So, the question is am I being overly concerned here ?

As a maker / seller of PWM fans in addition to PWM pumps, was hoping you could clarify your page a bit. Obviously putting a 4 pin PWM fan on a 3 pin / 4 pin DCV header loses low speed usability advantage but do we really need to worry about motor damage as Nidec describes within the warranty period of the fan ?


• PWM fans and pumps use the 4th pin (PWM Signal) input into an onboard controller that will modulate the voltage output to the windings (stator). This type of fan and pump will usually have a narrower voltage range, mainly to either protect the pump or compensate for the typically higher start voltage. While it is not recommended I wouldn’t expect any damage caused by lowering the voltage. The most important thing to watch out with this type of fans and pumps is input voltage modulation… Some companies came up with “PWM” controller which do not use that 4th pin but rather modulate the voltage input of the pump/fan. While this seems to have the effect, it does send a modulated voltage to the motor and its electronics. It’s the electronics part (which is here to generate modulation to the stator) that will eventually fail prematurely.
• 3-pin fans (non PWM, typically brushed DC motors) and brushed DC pumps will usually accept a much wider voltage range and are typically not subject to life degradation if the input voltage is modulated.

Regarding our specs, the minimum voltage that is shown typically reflects the minimum voltage to start the fan/pump. Low voltage should not affect the life of the product.

We do not recommend the use of input voltage modulation devices with our PWM products as the electronics that is in line with the stator will get damage by high frequency modulation (just as if you were switching on and off some electronics at a rate of roughly 25,000 times per second). Electrical motors won’t mind because of their electro-magnetic nature but electronics (semiconductor) will get damaged from this over time.

This is our engineer have to say. I hope this answered you questions.

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