Hamworthy hp BSEE Jun22 Ad 2.qxp_Layout 1 13/5/22 10:01 Page 1
ASK THE EXPERT Ask the Expert
Will Darby, managing director at Carlo Gavazzi UK Ltd, looks at how a faulty starting capacitor can lead to avoidable headaches
Can start problems be avoided on CSCR motors?
Yes, they certainly can. A faulty starting capacitor is often one of the most common causes of malfunction in single phase (CSCR) motors. Traditionally, CSCR motors incorporate two capacitors, but Carlo Gavazzi’s HDMS eliminates the need for a starting capacitor altogether. The patented High Dynamic Motor Starter (HDMS) features an innovative algorithm that ensures sufficient torque is generated to start a CSCR single phase motor. This type of motor is often used to drive equipment with a high starting torque such as scroll compressors used in refrigeration and pumping systems. If a start-capacitor deteriorates, the amount of the 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.
Can wear and tear on the motor be minimised?
Most definitely, 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 costly utility tariffs.
Can voltage fluctuations be stabalised?
An unstable power supply can cause severe problems but this can easily be fixed by removing the weakest link in the installation which is frequently the start capacitor.
Can adverse effects be avoided on equipment such as a heat pump?
Minimal downtime for any heat pumps is crucial. Our HDMS has been designed to ensure flawless motor performance. It features third generation self-
learning algorithms, which means the unit can continually improve motor starts without the need for user input. 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. A unique function of the HDMS is the high pressure function, which is designed to detect a locked rotor condition during start. Should this occur, the HDMS will increase the current limit to a maximum of 1.5 to 1.8 times the nominal current of the HDMS to try to start the motor within 1 second. If this is unsuccessful, the HDMS will activate the ‘end ramp-up’ alarm to protect the bypass relay from switching in at a high running load current. To reduce machine downtime and the need for user intervention the HDMS will follow an automatic recovery routine to re-start the motor.
In use, the HDMS’s Modbus RTU interface offers the option
for remote monitoring and quicker fault-finding via the history record, while also allowing connection to a PC for real-time monitoring of energy and operating variables.
12 MODELS 97 - 762kW OUTPUT COMBINE
Hamworthy’s Wessex ModuMax mk3
Up to 15:1 turndown ratio, 40°C delta T and 90°C output for top up and back up heat demands.
hamworthy-heating.com
enquiries@hamworthy-heating.com 01202 662500
Read the latest at:
www.bsee.co.uk
BUILDING SERVICES & ENVIRONMENTAL ENGINEER JUNE 2022 17
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