Abstract: A drive controller for a motor of a compressor includes a drive circuit that applies voltages to windings of the motor. The drive controller includes a speed control module that controls the drive circuit to rotate the motor at a requested speed. The drive controller includes a speed determination module that generates the requested speed. The drive controller includes a locked rotor protection module that identifies a locked rotor condition and, in response to identifying the locked rotor condition, instructs the speed determination module to power down the motor. The locked rotor protection module acquires an estimated speed of the motor upon expiration of a predetermined time interval that begins upon startup of the motor. The locked rotor protection module identifies the locked rotor condition in response to the estimated speed being lower than a threshold speed. The threshold speed is based on the requested speed.

Abstract: A drive system for an electrical load such as an electric motor or generator comprises a PWM converter and a controller therefore. A signal indicative of a condition of the converter outpost is used in a controller to drive an optimal value of PWM switching frequency based on a load characteristic that is used to control the pulse switching frequency. The system takes account of the overall system in deriving an efficient PWM switching frequency.

Abstract: A demountable electrical panel comprises a spring under tension that is easily assembled by being laid to rest in a recess in a mounting plate put under tension to make electrical contact with a circuit board when the device is assembled.

Abstract: A device for use with a printed circuit board, PCB, is provided. The device is arranged to electrically connect to a component on the PCB. The device comprises a first layer having a first hole therethrough and a second layer having a second hole therethrough. The second hole is arranged to receive a connector to connect the device to the PCB. Each of the first and second holes has a width in the plane of the respective first or second layer. The first and second holes are substantially coaxial. The width of the first hole is greater than the width of the second hole. Thus proper electrical clearance is provided between the component on the PCB an the device when the connector is not present.

Abstract: A DC motor drive (100) including power electronics (120) and control electronics (130). The power electronics (120) are arranged to receive a high voltage power supply and to controllably output that supply to a DC motor to controllably operate the motor. The control electronics (130) are arranged to receive a low voltage power supply and to control operation of the power electronics (120) and hence of the motor at least partly in response to signals received by the control electronics (130) indicative of at least one potential difference across the power electronics (120). The drive further includes a microprocessor (150) and an opto-coupler (170) arranged to sense the output of the power electronics (120) and to generate based thereon the signals in a form for optical transmission via opto-coupler (170) between the output of the power electronics (120) and the control electronics (130), thereby allowing galvanic isolation of the control electronics (30) from the power electronics (120).