Using VFD for single phase motor

Variable Frequency Drive (VFD), aka variable speed drive (VSD), generally it's using for controlling 3-phase AC motor in variable speeds. It's important to know, control 1-phase motor speed by a VFD may cause overheat of the motor, as well as the service life. It's recommended to upgrade the motor to three phase AC motor, which you can also connect the 3-phase motor to single phase power supply by using a single phase to three phase VFD, then control the speeds. Anyway, in technical it's possible to use a VFD for single phase motor speed controls, here ATO will show you details about running a single phase motor on a VFD.

I. Connect single phase VFD to AC power supply
For the purpose of illustration, ATO selected a 2 hp (1.5 kW) single phase VFD.

1. Connect VFD's GND terminal to ground.
2. Connect L and N terminals to AC power supply through a leakage protection switch.
   
3. Check if VFD's default display is working or not. If not, reset the VFD.
4. Be familiar with ATO single phase VFD's keypad. Generally, there are 8 key buttons on the VFD panel: RUN, STOP, PRG, DATA/ENTER, UP, DOWN, JOG and SHIFT. The keypad functions of different brand VFDs are basically the same. Besides, some VFDs have other function key buttons such as MONITORPDISPLAY and RESET.

II. Connect single phase induction motor to VFD and run without load

1. Connect VFD's U, V, W phase to induction motor's terminals correspondingly as show in following wiring instruction (The capacitors of single phase induction motor can be removed if necessary).
   
2. Set single phase VFD to keypad mode (P0-02).
   
3. Set types of motor (P1-00), rated power (P1-01), rated voltage (P1-02) and rated current (P1-03).
4. Set rated frequency of motor (P1-04) and rated speed (P1-05).
5. Use VFD to control single phase motor speed, the VFD's phase-loss function should be disabled, by setting P9-13 to 0, and then start to commissioning.
   
6. Press RUN, the frequency rises to 50Hz. Press SHIFT can switch display values. Let's switch to current (amps) display. The current displayed value must be less than or equal to the VFD's rated current.
7. If the current is too big, press STOP to stop running immediately. And then modify P0-15 value to 10 and P1-02 value to 160 to test again.
8. If the current is still too big, stop the VFD immediately. Switch over VFD's output U and W phase.
9. Function code P0-08 can be set to control the motor rated running frequency, set acceleration time by P0-17, set deceleration time by P0-18.
10. Be familiar with ATO single phase VFD protection code of errors. Observe the default value of thermal relay, the setting value of overload protection. These values can be modified if necessary.

III. ATO single phase VFD auto tuning mode
Using VFD vector control and torque control functions, need to use ATO single phase VFD auto tuning mode.

1. Auto tuning mode function code is P1-11. 0 means no action, 1 means motor static auto tuning, and 2 means motor rotation auto tuning.
2. Press DATA to save setting. At this point, the TRIP light flashes slowly. The digital displays TuNP. After pressing RUN, VFD starts auto tuning. It will last 1~5minutes. After finishing auto tuning, VFD will turn to initial interface.

IV. Commissioning of ATO single phase VFD with PC
After the basic settings of VFD, it can be connected with PC for the whole system commissioning. Connect the control lines of the VFD with the PC, and change the VFD operation mode to terminal control. According to the requirements of the PC system, set the VFD receive frequency signal range to 0~5V or 0~10V, and set the sampling response speed of analog frequency signal. If additional monitor is required, select the analog output monitoring item and adjust the range of this monitoring item terminal.

Terms: VFD, variable frequency drive, variable speed drive, adjustable speed drive, AC drive are the same meaning.

Buy single phase VFDs on ATO.com, power capacity starts from 1/2 hp, 1 hp, to 7.5 hp.