As noted above, VFDs are made to power a single motor (with a few exceptions) and not machines. Some additional information on how you have hooked up the VFD maybe a photo of the wiring and also the motor name plate. I am assuming you are running the VFD off of 230VAC @ 50Hz. You need to program the VFD and set the motor parameters.
P00.00 Line input frequency = 50Hz in the UK
P00.004 is the highest frequency/speed you want the motor to achieve, when it is = motor base frequency then maximum speed would be equal to the name plate listed RPM, you can go a bit higher but not much more with an older motor.
P00.05 is the motor base frequency listed on the name plate. This is the frequency the motor is designed to operate at.
P12.00 is the motor rated current
P12.01 is the motor rated voltage (which must be less than the VFD input voltage)
P12.02 is the motor number of poles, if it is a 1750 RPM motor than this would need to be set to 4.
P12.20 is the PWM frequency, in an older motor I would run it at 6kHz if you can live with it and no higher then 8.
Seems like this unit does not have sensorless vector control, it is only V/Hz which means the performance will drop off below around 25Hz. Sensorless vector uses motor feedback to more tightly control the motor performance.
VFD input 230VAC power is connected to the N and L terminals. Make sure the motor voltage is wired (220V) the same as the VFD voltage rating, often these machines are wired for higher voltages, and the motor will have little or no power if you have the motor voltage set incorrectly on the VFD.