Solid State relay kills induction motor fans

Deane Williams · Jul 28, 2015

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

John Robertson · Jul 28, 2015

On 07/27/2015 7:06 PM, 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

Have you had any other fans of the same make/model running on just
115VAC to see if they run any longer? They could be just cheap fans
whose oil dries up.

Hard to see where a SS AC Relay could hurt an induction motor if the
motor isn't overheating.

Does the fan still spin? Is there continuity in the winding?

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

N_Cook · Jul 28, 2015

On 28/07/2015 03:06, 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

Do you do TIG/MIG welding in this garage?

Jul 28, 2015

http://www.bcae1.com/relays.htm

Jul 29, 2015

On Tuesday, July 28, 2015 at 7:47:17 AM UTC-4, avag...@gmail.com wrote:
> http://www.bcae1.com/relays.htm

https://goo.gl/TCo6MH

Deane Williams · Jul 29, 2015

Hard to see where a SS AC Relay could hurt an induction motor if the
motor isn't overheating.

Does the fan still spin? Is there continuity in the winding?

John :-#)#

The motor still spins easily. There is no DC continuity from the power plug but I beleive this is normal for induction motors? Perhaps the overheat sensor has opened permenently. Home Depot gave me a replacement so I will try it again. These fans typically last for many years when plugged directly into a wall socket. This is a real mystery to me. Perhaps SS relays generate some large spikes on their output? I should check it with a scope.
Thanks for the comments.

Deane Williams · Jul 29, 2015

On Tuesday, July 28, 2015 at 3:15:20 AM UTC-4, N_Cook wrote:

On 28/07/2015 03:06, 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

Do you do TIG/MIG welding in this garage?

No. I don't own a TIG/MIG welder.

Deane Williams · Jul 29, 2015

On Tuesday, July 28, 2015 at 7:47:17 AM UTC-4, avag...@gmail.com wrote:
> http://www.bcae1.com/relays.htm

Thanks for the detailed treatise on mechanical relays. But I am using a solid state relay (SSR).

Pat · Jul 29, 2015

On Wed, 29 Jul 2015 08:12:51 -0700 (PDT), Deane Williams
<pyroartist.dw@gmail.com> wrote:

Hard to see where a SS AC Relay could hurt an induction motor if the
motor isn't overheating.

Does the fan still spin? Is there continuity in the winding?

John :-#)#

The motor still spins easily. There is no DC continuity from the power plug but I beleive this is normal for induction motors? Perhaps the overheat sensor has opened permenently. Home Depot gave me a replacement so I will try it again. These fans typically last for many years when plugged directly into a wall socket. This is a real mystery to me. Perhaps SS relays generate some large spikes on their output? I should check it with a scope.
Thanks for the comments.

You have an interesting problem. I hope you figure it out. I have
never used SS relays, but I can't image they cause spikes and other
anomolies that would kill a simple AC motor. Is the relay rated for
inductive loads?

By the way, I have a similar fan I purchased years ago. I just
measured its DC resistance and found it to be about 18 ohms on its
high setting. Clearly, that number is no indication of its impedance
at 60 Hz while in operation, but it definitely conducts DC. My best
guess is something is causing the motor windings to overheat and
eventually open. Unfortunately, I can't think of any way to explain
why that would happen.

Pat

Wolfgang Allinger · Jul 29, 2015

On 29 Jul 15 at group /sci/electronics/repair in article qf2irahhpfft1l1vnhbef69q2k01erc0qi@4ax.com
<pat@nospam.us> (Pat) wrote:

On Wed, 29 Jul 2015 08:12:51 -0700 (PDT), Deane Williams
pyroartist.dw@gmail.com> wrote:

Hard to see where a SS AC Relay could hurt an induction motor if
the motor isn't overheating.

Does the fan still spin? Is there continuity in the winding?

John :-#)#

The motor still spins easily. There is no DC continuity from the
power plug but I beleive this is normal for induction motors?
Perhaps the overheat sensor has opened permenently. Home Depot
gave me a replacement so I will try it again. These fans typically
last for many years when plugged directly into a wall socket. This
is a real mystery to me. Perhaps SS relays generate some large
spikes on their output? I should check it with a scope.
Thanks for the comments.

You have an interesting problem. I hope you figure it out. I have
never used SS relays, but I can't image they cause spikes and other
anomolies that would kill a simple AC motor. Is the relay rated for
inductive loads?

By the way, I have a similar fan I purchased years ago. I just
measured its DC resistance and found it to be about 18 ohms on its
high setting. Clearly, that number is no indication of its impedance
at 60 Hz while in operation, but it definitely conducts DC. My best
guess is something is causing the motor windings to overheat and
eventually open. Unfortunately, I can't think of any way to explain
why that would happen.

I think but don`t know!
If the SSR is bad (or not designed for inductive load) it may have
different half wave signals, so a DC current may flow thru the motor and
heats the coil (too much). A light bulb didn`t show any defects, because
it converts all current to heat and a little light

Just my 2 cent.

I will recommand a true mechanical relay for this job.

Saludos (an alle Vernünftigen, Rest sh. sig)
Wolfgang

--
Wolfgang Allinger, anerkannter Trollallergiker

reply Adresse gesetzt!
Ich diskutiere zukünftig weniger mit Idioten, denn sie ziehen mich auf
ihr Niveau herunter und schlagen mich dort mit ihrer Erfahrung!

(lt. alter usenet Weisheit) iPod, iPhone, iPad, iTunes, iRak, iDiot

MJC · Jul 30, 2015

In article <qf2irahhpfft1l1vnhbef69q2k01erc0qi@4ax.com>, pat@nospam.us
says...

On Wed, 29 Jul 2015 08:12:51 -0700 (PDT), Deane Williams
pyroartist.dw@gmail.com> wrote:
You have an interesting problem. I hope you figure it out. I have
never used SS relays, but I can't image they cause spikes and other
anomolies that would kill a simple AC motor. Is the relay rated for
inductive loads?

I can't be bothered to study SSRs so I just speculate... Could it be
that the ones you use just deliver one polarity of AC instead of both,
like a rectifier? Resulting in a DC component which the fans do not
like...

Mike.

Pat · Jul 30, 2015

On Wed, 29 Jul 2015 19:32:06 +0100, MJC <gravity@mjcoon.plus.com>
wrote:

In article <qf2irahhpfft1l1vnhbef69q2k01erc0qi@4ax.com>, pat@nospam.us
says...

On Wed, 29 Jul 2015 08:12:51 -0700 (PDT), Deane Williams
pyroartist.dw@gmail.com> wrote:
You have an interesting problem. I hope you figure it out. I have
never used SS relays, but I can't image they cause spikes and other
anomolies that would kill a simple AC motor. Is the relay rated for
inductive loads?

I can't be bothered to study SSRs so I just speculate... Could it be
that the ones you use just deliver one polarity of AC instead of both,
like a rectifier? Resulting in a DC component which the fans do not
like...

Mike.

That's an interesting thought. Even if most SSRs handle full AC,
maybe this particular one is faulty and only passes one polarity. That
would certainly make the fan motor unhappy.

Pat

whit3rd · Jul 30, 2015

On Monday, July 27, 2015 at 7:06:47 PM UTC-7, 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.,,, there is no smoke smell, no visible damage and if there is a capacitor it tests OK.

Three possibilities: your thermostat could be chattering (sending a bouncy-switch signal
to the SSR) and that is causing rectification. Your SSR could be a zero-crossing type, which
is exactly the most stressful motor-start situation (and an inexpensive motor might
take a magnetization at turn-off, then saturate at turn-on, and melt its fusible protector).
Third, the SSR might be susceptible to some other signal than your thermostat (RF
or maybe even input/output feedback oscillation).

If you use an AC relay, it cannot operate fast enough to rectify; if you feed that
AC relay with a triac-output optoisolator, with a smallish capacitor shunting
the input terminals (1 uF?), there ought to be no drive-side problems.

John Robertson · Jul 30, 2015

On 07/29/2015 11:40 AM, Pat wrote:

On Wed, 29 Jul 2015 19:32:06 +0100, MJC <gravity@mjcoon.plus.com
wrote:

In article <qf2irahhpfft1l1vnhbef69q2k01erc0qi@4ax.com>, pat@nospam.us
says...

On Wed, 29 Jul 2015 08:12:51 -0700 (PDT), Deane Williams
pyroartist.dw@gmail.com> wrote:
You have an interesting problem. I hope you figure it out. I have
never used SS relays, but I can't image they cause spikes and other
anomolies that would kill a simple AC motor. Is the relay rated for
inductive loads?

I can't be bothered to study SSRs so I just speculate... Could it be
that the ones you use just deliver one polarity of AC instead of both,
like a rectifier? Resulting in a DC component which the fans do not
like...

Mike.

That's an interesting thought. Even if most SSRs handle full AC,
maybe this particular one is faulty and only passes one polarity. That
would certainly make the fan motor unhappy.

Pat

The motor would run at half speed at best.

The motor won't overheat though unless it stalls/is jammed and can't
self cool.

It is more likely that the motors are just of a cheap quality
construction (for example are the UL or CSA rated?) and fail far too
easily. A SS AC modular relay is simply a high current TRIAC and these
are used on many fans around the world - what do you think a motor speed
control is?

A moments research pulled up this PDF:

http://www.omron.com/ecb/products/pdf/precautions_ssr.pdf

(quote)

The following will demonstrate the process to determine the effective
ratings of non-motor control rated Solid State Relays for use in motor
control applications:
Example question: Can I use a standard Solid State Relay (which is not
included in the Crydom Motion Control Brochure and therefore without HP
or KW Motor rating) to control the start/stop of a motor? The answer:
Yes, you need only to consider the motor nominal current value (FLA),
inrush current value (LRA), motor power factor (typically 0.1 to 0.9) to
select the appropriate turn-on switching type (zero-crossing or random)
and possible need for SSR transient protection to select an appropriate
Solid State Relay.

(end quote)

John :-#(#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

ScottWW · Jul 30, 2015

"Deane Williams" wrote in message
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

Some induction motors will have a thermal fuse incorporated onto the main
winding.
In the absense of a thermal fuse, this is my amateur speculation:
The switching of the SSR creates voltage spikes. Normally these are easily
absorbed by the induction motor. With enough time and heat, the lacquer
insulation on the motor windings gets brittle, thermal cycling compromises
its ability to insulate, then the voltage spikes begin jumping across high
potential areas (between winding ends or where wire leads are tied to
windings). If there is a capacitor involved, the arc is that much more
spectacular, and the motor's demise quicker.
Scott

M Philbrook · Jul 31, 2015

In article <d821f37c-370c-4030-b5b9-557793c313bc@googlegroups.com>,
pyroartist.dw@gmail.com says...

On Tuesday, July 28, 2015 at 3:15:20 AM UTC-4, N_Cook wrote:
On 28/07/2015 03:06, 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

Do you do TIG/MIG welding in this garage?

No. I don't own a TIG/MIG welder.

You need a non inductive load on the same circuit, along with a
capacitor across it..

Your motor windings are getting killed by the drop out of the TRIAC
at each phase angle. You need to suppress it somehow so that both the
HV pulse that shouldn't be there and lack of lower Z at the base of the
sine wave, for the motor and cap of the motor to properly operate..

These are cheap motors and they run warm to start with, minimum copper
and coating on the wire is used.

Try getting your hands on a motor run capacitor, somewhere around
3..5uf at the proper rated voltage and put that across the load side
of your SSR.

ALso, putting a non-inductive load on the output helps, too...

If you can get a low wattage incandescient bulb that would be fine or
maybe a 5 watt R at around 400 ohms or so across the SSR load, along
with the run cap.

Also, I suspect when you connect these components, you'll also hear a
slight difference of motor noise, which indicates this issue..

SSR switches don't always have a proper snubber in them, so you may
also want to use a 100R and .1 Cap in series around the SSR, back to the
soure so that the load will cycle back to the line on spikes.

Have a good day
Jamie

Jul 31, 2015

diode the relay

use the resistor

use 2 Tyco/Bosch mechanical relays with diodes for relays and inputs

Jul 31, 2015

On Wednesday, July 29, 2015 at 1:27:35 PM UTC-4, Pat wrote:

On Wed, 29 Jul 2015 08:12:51 -0700 (PDT), Deane Williams
pyroartist.dw@gmail.com> wrote:

Hard to see where a SS AC Relay could hurt an induction motor if the
motor isn't overheating.

Does the fan still spin? Is there continuity in the winding?

John :-#)#

The motor still spins easily. There is no DC continuity from the power plug but I beleive this is normal for induction motors? Perhaps the overheat sensor has opened permenently. Home Depot gave me a replacement so I will try it again. These fans typically last for many years when plugged directly into a wall socket. This is a real mystery to me. Perhaps SS relays generate some large spikes on their output? I should check it with a scope.
Thanks for the comments.

You have an interesting problem. I hope you figure it out. I have
never used SS relays, but I can't image they cause spikes and other
anomolies that would kill a simple AC motor. Is the relay rated for
inductive loads?

By the way, I have a similar fan I purchased years ago. I just
measured its DC resistance and found it to be about 18 ohms on its
high setting. Clearly, that number is no indication of its impedance
at 60 Hz while in operation, but it definitely conducts DC. My best
guess is something is causing the motor windings to overheat and
eventually open. Unfortunately, I can't think of any way to explain
why that would happen.

Pat

the thermometer rapidly operates relay on and off circuitry passing something of this to the fans who are confused square one without dioding separating the systems unbalanced properties.

Jul 31, 2015

AC relay with a triac-output optoisolator, with a smallish capacitor shunting
> the input terminals (1 uF?), there ought to be no drive-side problems.

///////////

they're mating

http://goo.gl/Dj00S9

David Lesher · Jul 31, 2015

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....

--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Solid State relay kills induction motor fans

Deane Williams

Guest

John Robertson

Guest

N_Cook

Guest

Guest

Guest

Deane Williams

Guest

Deane Williams

Guest

Deane Williams

Guest

Pat

Guest

Wolfgang Allinger

Guest

MJC

Guest

Pat

Guest

whit3rd

Guest

John Robertson

Guest

ScottWW

Guest

M Philbrook

Guest

Guest

Guest

Guest

David Lesher

Guest

Welcome to EDABoard.com

Sponsor

Online statistics

Forum statistics

Solid State relay kills induction motor fans

Deane Williams

Guest

John Robertson

Guest

N_Cook

Guest

Guest

Guest

Deane Williams

Guest

Deane Williams

Guest

Deane Williams

Guest

Pat

Guest

Wolfgang Allinger

Guest

MJC

Guest

Pat

Guest

whit3rd

Guest

John Robertson

Guest

ScottWW

Guest

M Philbrook

Guest

Guest

Guest

Guest

David Lesher

Guest

Log in

Welcome to EDABoard.com

Sponsor