Provide the X factor

A FAULTY starting capacitor is often one of the most common causes of malfunction in single phase (CSCR) motors. This type of motor is often used to drive equipment with a high starting torque such as scroll compressors used in refrigeration equipment and heat pumps. If a start-capacitor deteriorates, the amount of electrical charge stored can change, which can lead to problems with starting torque or tripping the motor's overload. Similarly, if the start capacitor short-circuits this could cause burn out.

Enhancing reliability

Carlo Gavazzi’s patented HDMS (High Dynamic Motor Starter) features an innovative algorithm that ensures sufficient torque is generated to start a CSCR single phase motor by eliminating the need for a start capacitor.  Carlo Gavazzi expect the HDMS to help manufacturers extend the lifetime and reliability of equipment reliant on a single phase CSCR motors.

Traditionally, CSCR motors have incorporated two capacitors:

- The start capacitor is used to increase the phase angle between the start and run windings of the motor. This helps create greater torque at start up and enables the motor to be cycled on and off rapidly. The start capacitor stays in the circuit long enough to rapidly bring the motor up to a predetermined speed, which is usually about 75% of the full speed, and is then taken out of the circuit.

- After this, the motor will work more efficiently with a run capacitor. The run capacitor will bring the motor's start winding back in phase with its run winding to provide the running torque once the motor is up and running. Run capacitors are designed for continuous duty while the motor is powered.

The HDMS has a maximum ramp-up time of 1 second, making it particularly suitable for starting scroll compressor motors which, generally, must start within 800 milliseconds to avoid excessive wear and tear on the orbiting scroll. In addition, the HDMS's algorithm will enable the motor to be started with less than 1.5 times the compressor's rated current.

A major advantage of the HDMS, when compared to direct online (DOL) starters, is that the soft starter can reduce start-up current by up to 75%, which can also help improve reliability by reducing alarms in applications with a weak power supply. And, in some instances, a lower start-up current might even help reduce utility tariff costs.  

HDMS features Carlo Gavazzi's third generation self-learning algorithms, meaning the unit continually improves motor starts without the need for user input. The unit is shipped with default current limit settings, equivalent to 1.5 to 1.8 times the rated HDMS current. For every motor start, the HDMS takes a number of measurements so that over time it will adjust the internal parameters to reduce the starting current during the subsequent motor start. And because the self-learning routine is active at every start the unit will ensure an optimal start even when load conditions change and when the motor ages.

Remote monitoring

The Modbus RTU interface offers the option for remote monitoring and quicker fault-finding via the history record, while allowing connection to a PC for real-time monitoring of energy and operating variables.

Furthermore, the unit's NFC feature enables stored data to be downloaded to any Android smartphone and tablet when the HDMS is in off-state to allow data to be downloaded and shared. The history file contains data on the first 8 starts, last 24 starts and up to 143 alarm events to facilitate troubleshooting. All data can be downloaded in .csv format to make it easy to share using a mobile phone.

Will Darby is managing director at Carlo Gavazzi

www.carlogavazzi.co.uk