Winding of single-phase fan motor with three or more speeds, can be very hard to replicate. In fact, that is a single-speed winding with additional winding for regulation.
This additional winding could cause the problem. Usually, is not worth to spend a lot of time with these inexpensive motors.
The following procedure can make the job easier in case when you want to make several speeds from one-speed fan and it is related to single-phase fan motors with run capacitor only. Note that the fan must be complete with fan blades (motor with empty shaft can not be used).
The procedure is very simple: a several additional capacitors should be connected in series with motor. The multiple trials will help to select most a suitable fan speeds ( two, three or more - six on the pic above). An additional capacitor will reduce the voltage on motor terminals. The larger capacitance - the larger voltage on motor terminals and larger rpm. Be careful, do not over-reduce the speed because the low speed will cause the poor cooling of motor.
In this case the speed with capacitor of 1 microF is to low ( voltage is only 100 V), but with 2; 3; 4; 5 microF and with no additional capacitor you can get five fan-speeds.
The benefit is the fact that you don't need any additional transformer to reduce the voltage and you can select the most appropriate speed that meet your needs.
The procedure is the same even for higher HP .
There is a lot of additional options regarding your voltage and rpm: for example a multiple capacitors in same small-size case can be used. See the photo below:
- The simplest way is use a inexpensive electronic regulator, like