Re: D1D40 SSR's burning out?? [TANKS]

["flier" <FLIER-at-sbcglobal.net>]

Hey Grant,

If the motors stall, the current will go to the max.  
I'm assuming the 15.4A spec is the typical current 
the motor will draw at a specified torque and at some 
duty cycle.  You may very well be coming close or 
exceeding the 40A rating of the SSRs if the motor is 
being 'held back'.  The D1D40 gets hot as heck 
dissipating the full 40A so they have to be mounted 
on a heatsink and may even need some cooling airflow 
to switch the full spec 40A.  Check out the D1D40 
heatsink specs.  Even at 15 amps or so they're gonna 
get up to 140 deg C!  Beyond 15A they must have a 
heatsink.

In a nutshell, protection diodes keep the SSRs from 
seeing back EMF from an inductive load like a motor.  
When the SSR breaks the circuit, the motor has some 
stored energy in it's coils that instantaneously 
feeds back to the open circuit.  The diode keeps the 
SSR from seeing that spike.  Just pick a fast 
switching diode say 1A with a voltage rating that's 
at least equal or a little greater than your supply 
voltage.  If 12V, then a 20V 1A switching diode will 
work.  It goes right across the motor.

Take care,

Ted 

--- Original Message ---
From: Grant Mahalek <gmahalek-at-shaw.ca>
To: tanks-at-rctankcombat.com
Subject: Re: D1D40 SSR's burning out?? [TANKS]

>Hey Ted,
>
>Thanks for the input Ted. I do not have any "protect 
diodes" installed in 
>the circuit.  Are you referring to the "Transient 
Protection" using fast 
>recovery diodes with PIV rated greater than the 
supply voltage as 
>illustrated/described on the www.crydom.com 
website.  Can you suggest what 
>type and size of diode to use and how/where to 
install these diodes.
>
>I'am assuming when you say "dissipation/max draw 
issue" you mean the motor/s 
>are drawing in excess of 40 amps which may be 
burning out the D1D40 SSR's. 
>The motors are only rated at 24vdc, 15.4 amps. I've 
taken the drive system 
>apart....without the tracks or motor connected the 
gear reduction runs 
>freely. In the field tests where the SSR's burned 
out I was using boat 
>roller drive wheels....this did'nt work.....the 
drive wheels slipped even 
>when I had the tracks so tight the 1/2" drive-shafts 
were bending under the 
>load.
>
>Could you please explain what you mean 
by "dissipation.....issue"? Any 
>suggestions how this problem could be corrected?
>
>Oh, one last thing, I was talking with an 
Electronics Technician yesterday 
>in the LHS, he feels there may be a problem with max 
current draw and 
>suggested installing resistors to limit the current 
flowing to the motors. 
>What do you think? Don't know what type or size or 
exactly where/how to 
>install.  Do you have any suggestions?
>
>Don't hesitate to provide technical answers as my 
buddy Mark Townsend, a 
>skilled electronics hobbyist is helping me out.
>
>I'am building new drive wheels today using plywood 
discs and rubber bungee 
>cord ie.-obviously a more successful design). I will 
be measuring the no 
>load and full load(ie.-transmission and tracks 
installed) current on the 
>bench today or tomorrow.
>
>Thanks again, any ideas are appreciated!
>
>
>Grant "thank goodnes for people more knowledgeable 
than me" Mahalek
>
>
>----- Original Message ----- 
>From: "flier" <FLIER-at-sbcglobal.net>
>To: <tanks-at-rctankcombat.com>
>Sent: Thursday, November 03, 2005 8:44 AM
>Subject: Re: D1D40 SSR's burning out?? [TANKS]
>
>
>> Hey Grant, it's Ted Callahan.
>>
>> If your max current is significantly below 40A, 
then the prob may be back 
>> EMF where the protect diodes come in although I'm 
skeptical.  I think you 
>> may have a dissipation/max draw issue.
>>
>> Regards,
>> Ted
>>
>> --- Original Message ---
>> From: Grant Mahalek <gmahalek-at-shaw.ca>
>> To: tanks-at-rctankcombat.com
>> Subject: Re: D1D40 SSR's burning out?? [TANKS]
>>
>>>Flier,
>>>
>>>Thanks for the suggestion.  I will be measuring 
the max current draw 
>>>today.
>>>Oh by the way, what's your name....I'd like to 
address you by your name.
>>>
>>>Grant "I'am learning every day" Mahalek
>>>
>>>
>>>----- Original Message ----- 
>>>From: "flier" <FLIER-at-sbcglobal.net>
>>>To: <tanks-at-rctankcombat.com>; 
<tanks-at-rctankcombat.com>
>>>Sent: Wednesday, November 02, 2005 7:15 AM
>>>Subject: Re: D1D40 SSR's burning out?? [TANKS]
>>>
>>>
>>>> Grant,
>>>>
>>>> Have you measured your max current draw?
>>>>
>>>>
>>>> --- Original Message ---
>>>> From: Grant Mahalek <gmahalek-at-shaw.ca>
>>>> To: tanks-at-rctankcombat.com
>>>> Subject: Re: D1D40 SSR's burning out?? [TANKS]
>>>>
>>>>>Hi Norm,
>>>>>
>>>>>In Test #1 the right SSR got very hot.
>>>>>
>>>>>I forgot to check the SSR temperatures in Test#2.
>>>>>
>>>>>Grant
>>>>>  ----- Original Message -----=20
>>>>>  From: Norman Wieser=20
>>>>>  To: tanks-at-rctankcombat.com=20
>>>>>  Sent: Tuesday, November 01, 2005 9:08 PM
>>>>>  Subject: Re: D1D40 SSR's burning out?? [TANKS]
>>>>>
>>>>>
>>>>>  Hi Grant
>>>>>
>>>>>   Did the SSR's get very Hot ?
>>>>>
>>>>>  Norm
>>>>>    ----- Original Message -----=20
>>>>>    From: Grant Mahalek=20
>>>>>    To: tanks-at-rctankcombat.com=20
>>>>>    Sent: Tuesday, November 01, 2005 6:27 PM
>>>>>    Subject: Fw: D1D40 SSR's burning out?? 
[TANKS]
>>>>>
>>>>>
>>>>>    Hi there,
>>>>>
>>>>>    I've run into a bit of a problem in the
>>>> construction of my Hetzer.  =
>>>>>I've burned out three Crydom SSR's with my 
Anvilus
>>>> proportional motor =
>>>>>controller.  I've sent off an email to
>>>> www.crydom.com today in hopes of =
>>>>>getting some suggestions.  The Crydom website
>>>> mentions something called =
>>>>>"Transient Protection" and protection of the 
SSR's
>>>> using fast recovery =
>>>>>type diodes with PIV rated greater than supply =
>>>>>voltage(....cool....unfortunately I don't 
completely
>>>> understand this). =
>>>>>Has anyone out there
>>>>>
>>>>>    In the "Tri-Pact News Service" article
>>>> entitled "R/C Combat Vehicles =
>>>>>Speed Controls" under the section "Other Issues"
>>>> various devices are =
>>>>>recommended to limit power surges and radio
>>>> interference.  After a small =
>>>>>fix(installation of a CMOS NAND 4011 Gate) into 
the
>>>> steering and =
>>>>>throttle servo leads, radio interference is no
>>>> longer a problem.
>>>>>
>>>>>    However, burning out these SSR's is becoming 
a
>>>> bit of a =
>>>>>pain....xxo!!/?##.
>>>>>
>>>>>    Can anyone out there offer suggestions, 
detailed
>>>> or otherwise on how =
>>>>>to overcome this obstacle?  Any suggestions 
would be
>>>> much appreciated.
>>>>>
>>>>>    Oh, by the way, the rubber boat roller drive
>>>> wheels did not work, =
>>>>>the rubber was too hard and the drive wheels 
slipped
>>>> in the tracks.  =
>>>>>I'am going to use the "tried and true" TTS rubber
>>>> bungee cord wrapped =
>>>>>plywood drive wheels.  And for those of you
>>>> wondering about what =
>>>>>thickness of drive-shaft to use, I support Steve
>>>> Tyng's suggestion to =
>>>>>use a hardened steel shaft > 1/2 inch.  I've 
already
>>>> bent both my 1/2 =
>>>>>inch drive shafts in the minimal testing I've 
done
>>>> so far.
>>>>>
>>>>>    Supper call....thanks for any help you guys 
can
>>>> offer.
>>>>>
>>>>>
>>>>>    Grant P. Mahalek
>>>>>
>>>>>    ----- Original Message -----=20
>>>>>    From: Grant Mahalek=20
>>>>>    To: support-at-crydom.com=20
>>>>>    Sent: Tuesday, November 01, 2005 7:33 AM
>>>>>    Subject: D1D40 SSR's burning out??
>>>>>
>>>>>
>>>>>    Hello there,
>>>>>
>>>>>
>>>>>    I'am a hobbyist using a pair of Crydom D1D40
>>>> SSR's with a motor =
>>>>>controller to provide proportional speed control 
for
>>>> a custom built 1:6 =
>>>>>scale radio control combat tank. The motor 
controller
>>>> (Anvilus RC Relay =
>>>>>SSR Motor Controller; Board h_050412, Manual 
050425)
>>>> is described in =
>>>>>detail at www.anvilus.com . The motor and control
>>>> system is wired =
>>>>>according to figure 3, page 5 of the manual.  
I'am
>>>> using a pair of new =
>>>>>electric scooter motors(MY1016) from
>>>> www.unitemotor.com operated at =
>>>>>24Vdc. Motor specifications: 24Vdc, 2750 rpm,
>>>> 15.4amps, 280watts. There =
>>>>>is a 40 amp automotive fuse installed in-line on 
the
>>>> each motor power =
>>>>>lead.  No other circuit protection is provided.
>>>>>
>>>>>    I have burned out three(3) Crydom D1D40 SSR's
>>>> thus far.  This is =
>>>>>getting a little expensive for a hobby......
>>>>>
>>>>>    Can you help?
>>>>>
>>>>>    Circumstances of failures:
>>>>>
>>>>>    1.)Test #1; left SSR failed; left SSR -1
>>>> terminal wires became loose =
>>>>>during tank test run. Up to this time(20 minutes 
of
>>>> run time), the =
>>>>>electronics and drive system were operating with
>>>> full mixing and =
>>>>>proportional speed control.  Right drive motor 
and
>>>> right SSR became very =
>>>>>hot.
>>>>>
>>>>>    2.)Test #2; right SSR failed after about 20
>>>> minutes of fully =
>>>>>proportional run-time. No apparent loose 
electrical
>>>> connections. No =
>>>>>apparent mechanical binding in drive-train. Right
>>>> drive motor became =
>>>>>very hot.
>>>>>
>>>>>    Apparently, there are twenty to thirty RC 
combat
>>>> tanks using the =
>>>>>same electronics(with Crydom SSR's) and drive
>>>> systems with almost =
>>>>>identical components with no problems.
>>>>>
>>>>>    Do you have any suggestions regarding the
>>>> inclusion of circuits or =
>>>>>components to protect the SSR's from being burned
>>>> out.  Could you please =
>>>>>be very specific with any suggestions regarding
>>>> protective circuits or =
>>>>>components(ie.-component/circuit installation 
into
>>>> motor control wiring =
>>>>>and type and specific sizes of and sizes of any
>>>> components).=20
>>>>>
>>>>>
>>>>>    Thank you,
>>>>>
>>>>>
>>>>>    Grant P. Mahalek
>>>>>    gmahalek-at-shaw.ca
>>>>>    403-948-6443(res)
>>>>>    403-880-2070(bus, cell)
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>> 
>
>