HowTo: Increase Motor Power Output and Speed by 73%

A 73% increase in Speed and Power is available from most all small AC motors. The same for larger motors when purchased with a special winding. Simply use a 230V x 50Hz motor at 400V x 87Hz, when supplied by an Inverter Drive.

This is because a 400V Inverter controls Voltage and Frequency through 230V x 50Hz on its way to 400V x 87Hz. The motor remains correctly fluxed all the way through to 87Hz. Set the 400V Inverter 'Base Frequency' to 87Hz. This is near enough the same for 220V and 240V Motors. For 240V x 60Hz motors, set the base frequency to 104Hz.

Above 50Hz the motor will be capable of more power in proportion to its speed above 50Hz, as far as 87Hz. In practice many motor manufacturers reduce the 87Hz output slightly to suit the increased losses at the higher frequency. If in doubt ask us.

The Inverter provides protection from motor over-current (when correctly set). Most motor manufacturers will approve use of their 240V motors at 400V, as long as they are correctly fluxed. Marelli, Brooks and Leroy Somer have in the past.

The maximum speed will be around 2 x 87Hz or 2 x 104Hz.

If the requirement is to reach high speeds with a standard AC motor, a small 2 pole motor can be run to 7000RPM or 8000RPM, with only special balancing to reduce the bearing loads. If this is your requirement, please ask and we will check with the Manufacturer and offer a suitable motor.

If the requirement is to increase the speed of an existing conveyer type application, this solution provides increased speed and power in line with the needs of the application. This as long as mechanical limits are not exceeded. Gear-motors with 4 pole motors fitted, can usually be run at 2500RPM to 3000RPM without difficuly and are usually sized for torque (Nm - twisting moment) not kW.

Most small motors are arranged for 230/400V x 50Hz supply for Delta/Star connection, so can be run from an Inverter Drive at 400V x 87Hz with Delta connected windings. This is the standard arrangement for motors up to around 3kW, depending on the manufacturer. Larger motors will need to be ordered at 240V, use the search facility on the site for 230V motors or ask us .

The parameter to set is 'Base Frequency' or 'Nominal Frequency' (depending on the Inverter manufacturer) in the motor settings of the Drive unit.

Size the drive to suit the motor full load current (not kW).