I have a 220volt high and low speed motor. I would like to control both speeds with Arduino and Solid State Relays. How would you hook this up with relays to control the two different speeds?
Thank You
Sprinkfitter
SSRs are just switches, so use them as switches.
I suspect you could run into a very serious problem if both connections to the motor were activated at once.
AC induction motor inrush current is five to ten times the running amps, depending upon motor design - which is why you find mechanical contactors used for across the line motor control. It is not an application for SSR's.
Don't ignore proper overcurrent protection as well as motor thermal protection to meet NEC requirements.
A suitable contactor (you need two):
Use something like one of these to control the contactors from the Arduino:
What makes the contactor better than a solid state switch? I was thinking i have seen AC motors switch with ssr. Also is there any way you can be sure that both high and low speed line will never be turn on together other than in the code
SSRs are fine to use with AC induction motors, if you take into account the startup current.
I've been running two 220VAC 1.5 HP deep well pumps with 380VAC, 40 Amp SSRs for years without any problems.
However, with your motor, I would indeed worry about some unanticipated failure that connects both the low and high speed terminals at the same time, and probably would not do it with SSRs. Better to use a heavy duty relay to make the switchover, so that it is impossible to have both modes powered. The contactor mentioned above solves both problems.
jremington:
SSRs are fine to use with AC induction motors, if you take into account the startup current.I've been running two 220VAC 1.5 HP deep well pumps with 380VAC, 40 Amp SSRs for years without any problems.
However, with your motor, I would indeed worry about some unanticipated failure that connects both the low and high speed terminals at the same time, and probably would not do it with SSRs. Better to use a heavy duty relay to make the switchover, so that it is impossible to have both modes powered. The contactor mentioned above solves both problems.
Thank you for your advise. I believe you are right and I will use the contractor relay. Should I use 3 relays to switch from high to low on this 220 volt motor. Again thank you for your help
I goofed with that eBay listing. You'll need 2 each two pole contactors (not single pole) due to the motor being 240 volt. You need to disconnect both motor leads to meet the US electrical code (NEC). The motor nameplate shows it has internal thermal protection so you only need to provide over current protection.
What makes the contactor better than a solid state switch?
Mechanical contactors are significantly more robust that SSR's. When they do fail, they generally fail open. SSR's will fail closed which results in a motor that never stops. Specifically, in your application, you'll clear fuses or a breaker when one of the two SSR fails and both windings are energized at the same time.
I was thinking i have seen AC motors switch with ssr.
It can be done. But an SSR that is properly sized will cost significantly more than a mechanical contactor, consume more space and waste more energy than a contactor. With your motor, it appears to be nameplated at 15.0 amps on high speed. That means that you need at an absolute minimum a 75 or 80 amp contactor, 100 amps or more would a safer number. You would have to ask USEM to know for sure.
IMO, the only valid reason to use an SSR in place of a contactor is duty cycle. If you have a load that turns on and off multiple times per minute, a mechanical contactor will quickly reach its rated contact cycle count at which point the contacts are at end of life and will eventually fail to make contact.
SSR's do not have a cycle count rating but they eventually fail due to repeated thermal stresses caused by heating and cooling of the semiconductor die. Eventually the die bond fails or a wire bond fails then another fails and another... with the result being a fused mass of silicon and aluminum. The worst situation with an SSR is where the device runs at high loads, runs long enough to reach high die temperatures then be off long enough to cool back down close to ambient. This creates the maximum thermal stress on the die bond and eventually results in the destruction of the device.
If you on/off duty cycle is low, one where you don't do 100,000 to 1M cycles in five to ten years, there is zero reason to even consider an SSR.
Also is there any way you can be sure that both high and low speed line will never be turn on together other than in the code
It can be done with a single, two pole mechanically interlocked contactor but this is overkill for most applications. The usual solution is an additional normally closed auxiliary switch on each contactor that is in series with the coil of the other contactor. If one contactor is closed, you cannot get energy to the second coil.
It cannot be done with SSR's without resorting to current sensing techniques.
FWIW, after editing the beginning of the post to clarify the two pole contactor requirement, I'll add that if you did use SSR's, you'd need three of them to meet code.
Here's a typical two pole contactor:
Awesome information!!! Thank you for pointing me in the right direction. 
Great forum!!! Glad I found this wealth of information.
Sprinkfitter