I dont need to control the speed. What is the easiest way to convert and what would be the least expensive way. Thanks.
I am no expert on this, but it is a simple case of stepping down the 110V AC source to 90V AC, and rectifying the transformer output to DC.
What is the nameplate rating for this motor ? Voltage Running current Locked rotor current You will have to get a AC-to-DC power supply, it can be made from an autotransformer and rectifier bridges, but it won't be inexpensive, or you can buy an industrial power supply for several hundred dollars. I could not find one on Google with a quick search; that motor is too large for the 2-horsepower supplies I did find. A 2.25 hp motor is difficult to start and run on 110 V AC power because the running current will be a minimum of 15 amperes, thus requiring a sized 20 amp or larger. You will need motor overload circuit protection which is sized for the current requirements of the motor. The starting current for the motor, if the motor has a heavy load, will be more than a 20 amp breaker can handle, so you really need 30-amp service.
I do not recommend inexpensive ways of doing it as you may end up throwing away lots of money from failures and put yourself at risk of fire or shock. The transformer alone for this power requirement costs more than a proper thyristor type DC motor controller.
A transformer and a bridge rectifier would work. The transformer needs to be a primary 110 to secondary 90 volts AC rated at 1700 VA. Or a smaller transformer, say 110 volts to 20 VAC rated at 300 VA, wired in series opposition to the 110 volt line, followed by the rectifiers. Be sure that you really have a 110 volt line, not 120 volts, as that changes the numbers. US nominal is between 117 and 125 volts, depending on where you live. Another alternative is to just rectify the AC via a bridge rectifier which gets you about 110 VDC, and use a switching circuit to reduce that to 90 volts DC. This would be a lot lighter but a lot more expensive.
