Solid State relay kills induction motor fans

[Phil Allison]

David Lesher wrote:

Deane Williams <pyroartist.dw@gmail.com> writes:


The motor still spins easily. There is no DC continuity from the power p=
lug but I beleive this is normal for induction motors? Perhaps the overheat=
sensor has opened permenently.

You got it. As they age the bearing dry and they pull more current.
Eventually they open the Microtemp protecter within....

** "The motor still spins easily" contradicts that idea.

Seen a few cheap Chinese fans with tight/stuck bearings - takes a fair bit of solvent to get them spinning again.

The OP has no so far bothered to open a fan a check the motor wiring for continuity.


.... Phil

 

[Ron D.]

Deane:

What relay are you using?
What is the the motor?

Some SSR bricks designed for this purpose have 3-32 V for an input and no series resistor is required. A heat sink with the appropriate thermal grease is. They have to be triac or back to back SCR's.

Some offer to switch at zero current. It should be random.

Some require series resistors.

Some SSR's are triacs, dual SCR's, SCR's (won;t work) or MOSFETS (won;t work).

 

On Tuesday, July 28, 2015 at 10:06:47 AM UTC+8, Deane Williams wrote:

I set up a thermostat in my garage that comes on at 80 degrees F. and sends a 6 VDC battery voltage to control a 120 VAC solid state relay which powers up the vent fan. The fans always quit within 2 months to a year with no obvious defects. These are inexpensive 20 inch box fans with induction motors. I have tried several brands and styles of fans. The latest was a Home Depot unit that only lasted 2 months.
Does anyone know of a reason why I can't run an induction motor from a SS relay? What is killing the fans? I have taken two apart and there is no smoke smell, no visible damage and if there is a capacitor it tests OK.
Thanks for any ideas. I am going to switch over to a mechanical relay.

Dean

If you need the thermal fuse, please feel free to contact xx.liu@setfuse.com.
We are thermal fuse, MOV and thermal protected MOV manufacturer in China.

Any question, please do not hesitate to inform us.

Best Regards
Leo

 

[M Philbrook]

In article <1e2c15cf-b258-48ec-a2bc-d045a026e3e3@googlegroups.com>,
pallison49@gmail.com says...

David Lesher wrote:

Deane Williams <pyroartist.dw@gmail.com> writes:


The motor still spins easily. There is no DC continuity from the power p=
lug but I beleive this is normal for induction motors? Perhaps the overheat=
sensor has opened permenently.

You got it. As they age the bearing dry and they pull more current.
Eventually they open the Microtemp protecter within....



** "The motor still spins easily" contradicts that idea.

Seen a few cheap Chinese fans with tight/stuck bearings - takes a fair bit of solvent to get them spinning again.

The OP has no so far bothered to open a fan a check the motor wiring for continuity.


... Phil

Yes he did, There is no continuity.. Which means it's been operating
hot!

Jamie

 

[petrus bitbyter]

Deane Williams <pyroartist.dw@gmail.com> wrote in
news:f6c5bb01-51c2-4824-89a9-c7a84aa07ae0@googlegroups.com:

I set up a thermostat in my garage that comes on at 80 degrees F. and
sends a 6 VDC battery voltage to control a 120 VAC solid state relay
which powers up the vent fan. The fans always quit within 2 months to
a year with no obvious defects. These are inexpensive 20 inch box fans
with induction motors. I have tried several brands and styles of fans.
The latest was a Home Depot unit that only lasted 2 months.
Does anyone know of a reason why I can't run an induction motor
from a SS relay? What is killing the fans? I have taken two apart
and there is no smoke smell, no visible damage and if there is a
capacitor it tests OK.
Thanks for any ideas. I am going to switch over to a mechanical relay.

Dean

So you blew some fans. But what about the SSR? Is it suited for diving
these motors? Some properties are as important as properties of a
mechanical relay and even with the right specs it may be defective.

Then, what about the signal diving the SSR? If it comes from a mechanical
switch, the contactbounce can damage or destroy the SSR which in turn can
blow the motor(s). SSRs like to be driven by clean signals and tend to be
much more unforgiving them their mechanical couterparts.

petrus bitbyter

 

[Phil Allison]

M Philbrook wrote:

" The motor still spins easily. There is no DC continuity from the power plug but I beleive this is normal for induction motors? "

The OP has no so far bothered to open a fan a check the motor wiring for
continuity.


Yes he did, There is no continuity..

** ".. from the power plug ... ".

Box fans typically have timers, 3 way speed controls and tilt switches, any of which could be the real problem.

Which means it's been operating hot!

** Not likely with perfectly free bearing and no damage.


..... Phil

 

[John Robertson]

On 07/31/2015 7:42 PM, Phil Allison wrote:

M Philbrook wrote:

" The motor still spins easily. There is no DC continuity from the power plug but I beleive this is normal for induction motors?"


The OP has no so far bothered to open a fan a check the motor wiring for
continuity.


Yes he did, There is no continuity..


** ".. from the power plug ... ".

Box fans typically have timers, 3 way speed controls and tilt switches, any of which could be the real problem.


Which means it's been operating hot!


** Not likely with perfectly free bearing and no damage.


..... Phil

Hi Phil,

I don't think anyone read my quote (July 29) from a SSR (Omron)
manufacturers' FAQ PDF about using non-motor rated SSRs with induction
motors. As they said, as long as the SSR has sufficient rating to handle
the start up current (etc.) there will be no problems for the SSR.

The only thing folks haven't considered is a voltage surge - that could
take out the fan without harming the SSR. The wiring may have problems
where the neutral fails in a sub-box leading to 240VAC going to a motor
designed for 120 - the motor would not last long, yet wouldn't give
obvious signs of failure as the internal overheat fuse would open
quickly...

I have no other ideas unless he isn't giving the house elves enough food
and clothing.

John :-#(#

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