# Need some help designing a mains frequency converter (220v/50hz input, 220v/60hz output) for <$200USD My main limitations here are with the amount of power needed, and of course the price. What I'm trying to do is to run a clothing dryer from the USA in another country, without burning out the drum motor again. As I have to replace the motor already, I could either build/buy a frequency converter, or try to find a motor rated for 50hz instead (assuming the dryer doesn't use a transformer, otherwise I might be able to replace that instead...?) The odd thing is that both the manufacturer's website AND the label on the dryer itself list "220v 50/60hz," though the drum motor died prematurely. There's also no warranty since the dryer was exported. Costs: ~$300USD (motor - required as current one died) ~$1,000USD (the "cheapest" new dryer, if buying locally) ~$3,000USD (cheapest frequency converter I could find >7kVa)

Specifics: Power desired : 220v, 15a, 60hz. Mains power: 220v, 15a, 50hz.

While I can readily find devices that convert both voltage AND frequency for a decent price, I'm not finding anything that converts JUST frequency for less than $3,000 USD; at least, none that are designed for ~7.5kVa and run on 220v. Hence my interest in building one. While I have had no formal schooling specifically in electronics or electrical engineering, I am quite experienced thanks to the vast amount of electrical repairs I do in my work. I can read diagrams, write my own while examining/tracing circuits, and I am comfortable with PCB's and related soldering. I'm asking this here, because I honestly have no idea where a better place to ask would be. It's unfortunately not a super-specific question, though it IS an electrical/electronic engineering conundrum. -UPDATE- After removing the dead motor, I have additional information. The label on the dead motor states: 1/3hp 120v/60hz/6.1A. so even though the dryer sticker specifically shows 50/60, the actual motor isn't "both." I'm now looking for a 50hz version of the OEM motor, though progress is slow.... Thankfully, the motor turns both the drum AND the blower, which means no other moving part will be impacted by the frequency change. If anyone has a "trusted" and knowledgeable source (other than Grainger, whom I'm about to contact) for such things, I'll gladly listen (or read...?). • "'m not finding anything that converts JUST frequency" probably because, when you have to change the frequency, the change in voltage comes along almost for free. " I am quite experienced ..." I am afraid this is still out of your league. Just buy a new dryer or motor. – Oldfart Jan 6 at 17:05 • You say that the dryer is specified to work on 50 or 60 Hz. How do you know that your motor failed because of the power line frequency? It seems to me that you are trying to solve a problem that doesn't exist. – Barry Jan 6 at 18:20 • The title of your question says you want to spend ">$200"...doesn't $3000 fulfill that requirement? – Elliot Alderson Jan 6 at 18:44 • You might want to consider having the damaged motor locally rewound or replaced with something intended for 50 Hz. Electronic power conversion is just not economically reasonable, at least unless you can apply it to just the motor and not the heating elements. Try to find a local shop that does motor rewinding and related repair. – Chris Stratton Jan 7 at 2:47 • Good ways to kill a motor: Heat death/overcurrent, particle/fluid ingress, corrosion/humidity/moisture(may want to investigate this in the carribean), overvoltage/inductive spike. No reason you can't find a compatible motor rated specifically for 50hz, but inspect the damaged motor and see if any of these other things were a concern. – K H Jan 7 at 2:54 ## 1 Answer Check the dryer information to be sure there is not some change required for 60 Hz. The motor speed at 60 Hz is 20% higher resulting at least 20% more power unless the speed is mechanically reset to the 50 Hz speed. At 7500 watts, I assume this is an electrically heated dryer with a much smaller power requirement for the motor. If that is the case, you could use a much smaller converter if you could power it separately. Also,$1000 USD seems high for a dryer, but you may be living in an expensive place.

• Nothing indicates any change being needed. And as stated above, the actual dryer is an American model (meant to connect to 60hz), but is connected in a country based on 50hz. The mains voltage is identical to the US, but the frequency isn't.. My understanding is that, when run by 50hz, an induction motor will end up running ~20% slower than if it was run by it's design spec, preventing it from exceeding the torque needed to start a stationary drum, and this condition is what burned out the motor. – LudivousKain Jan 7 at 1:45
• And to answer your initial comments: Yes it is an electrically-heated dryer. And YES it is extremely expensive down here... In much of the the Caribbean, it usually works out cheaper to buy things in the USA, ship them down here, AND to also pay the import duty. After all, the businesses here pay the same amount and same fees, but they tack on extra so they can make a profit as well. – LudivousKain Jan 7 at 1:48
• I misunderstood the input vs output frequency. You are correct about the speed. If the motor is truly rated 50/60 Hz, It 230 V, 60 Hz is the optimum design operating voltage, the optimum voltage of 50 Hz would be 20% lower or 184 V. It could require a wiring change with the motor connection that is not in your documentation, or the motor could be designed for something like 220 V +/- 25%. Perhaps the motor is not what it is advertised to be. It also could be a defective product. Look for a repair shop that will guarantee the repair. – Charles Cowie Jan 7 at 3:54