An inductive power transfer system, comprising a primary side unit and a secondary side unit, the primary side unit having a switched mode power supply (SMPS), a transmission coil and a controller, and the secondary side unit having a receiver coil, a controller and a load, wherein the secondary side controller is configured to detect the secondary voltage in the receiver coil and to transmit the value of the secondary voltage to the primary side controller thereby requesting an increase or decrease in the power transmitted from the primary side according to whether the secondary voltage in the receiver coil is above or below a predetermined value, characterised in that the primary side controller is configured to set an operating frequency of the SMPS, during start-up of the SMPS, by a) setting the operating frequency to a maximum value and gradually reducing the frequency until a control signal is received from the secondary side unit; b) transmitting a command signal to the secondary side unit to switch the secondary load to zero and transmitting the secondary voltage measurement to the controller; c) comparing the secondary voltage determined in step b) with the desired secondary voltage and, if the determined secondary voltage is not within a design margin of the desired secondary voltage, comparing the frequency with a system minimum frequency and if it is less than the minimum recommencing the start-up or otherwise repeating steps b) and c); d) if the determined secondary voltage is within a design margin of the desired secondary voltage, determining the operating frequency required to achieve the desired voltage in the secondary unit adjusting for the actual spacing between the primary and the secondary units; and wherein the primary side controller is configured to set the operating frequency of the SMPS during a start-up procedure of the SMPS, by e) configuring a control loop speed according to the operating frequency so determined, thereby completing the start-up procedure of the SMPS. a) setting the operating frequency to a maximum value and gradually reducing the frequency until a control signal is received from the secondary side unit; b) transmitting a command signal to the secondary side unit to switch the secondary load to zero and transmitting the secondary voltage measurement to the controller; c) comparing the secondary voltage determined in step b) with the desired secondary voltage and, if the determined secondary voltage is not within a design margin of the desired secondary voltage, comparing the frequency with a system minimum frequency and if it is less than the minimum recommencing the start-up or otherwise repeating steps b) and c); d) if the determined secondary voltage is within a design margin of the desired secondary voltage, determining the operating frequency required to achieve the desired voltage in the secondary unit adjusting for the actual spacing between the primary and the secondary units; and wherein the primary side controller is configured to set the operating frequency of the SMPS during a start-up procedure of the SMPS, by e) configuring a control loop speed according to the operating frequency so determined, thereby completing the start-up procedure of the SMPS.