Motor+mechanical abrasive stepless speed regulator：the speed regulator changes the speed by manual adjustment，which is safe，reliable and infinitive flow adjustment．But thenon-automatic adjustment is also troublesome. Speed regulating should be done in operation not in shutoff state．Pleasereferto manufacturer instruction for maintenance and service．

Motor+fixed relative ratio speed reducer：the driving is easy with cons-tant rotary speed of the rotor，which also leads to nonadjustablity of flow

Frequency transformed motor+frequency transformer：it realizes both automatic adjusting and infinitive adjustment of flow．It is highly automatic and has large torque in low speed．But the frequency transformer is expensive.ase refer to manufacturer instruction for maintenance and service．