Hybrid motor starters benefit control panel design

Have you noticed how a new generation of electronic hybrid motor starters is changing the way industry is controlling motors? Hybrid motor starters are becoming popular because they simplify installation, reduce equipment size, and lower installation costs for small motors. They offer reliable motor switching and are available with options like safe shutdown to SIL3/PLe and built-in communications.

They use a modular 22.5mm wide DIN rail mounting construction suitable for panel mounting control of AC motors. Hybrid motor starters are suitable for forward and reverse DOL starting of asynchronous A.C. induction motors up to 4kW. They are not generally used or sold as stand-alone wall mounting starters. Importantly, they replace the contactor(s) and motor overload relay and are available from several manufacturers including Phoenix Contact and Schneider Electric.

 DOL motor starters

Traditional mechanical direct online (DOL) motor starters are so commonplace we do not even notice having them around. For many years they were the simplest way to start small motors and often used in wall mounting designs. They generally comprise of start/stop buttons, contactor, motor overload relay, and for a reversing motor, two interlocked contactors. They offer no intelligent communications and use auxiliary switches for signalling and to show their status.

Hybrid motors starters have similar functions but offer forward running, reverse running and motor protection in a single unit. As with mechanical motor starters, they need short circuit protection offered by a motor breaker or fuses. But the Phoenix Contactron series has an optional unit with integrated fuses offering type 2 protection to IEC/EN 60947-4-2. The Schneider TeSys H offers type 1 protection when used with its GV2L motor breakers. Depending on the manufacturer networking options are also available.

 What are hybrid motor starters?

The term hybrid motor starters describe the dual switching action at the heart of these microprocessor-controlled starters. On starting, wear-free semi-conductors switch the initial motor load current. Once started, a mechanical relay bypasses the electronic switch and remains closed while the motor is running. When stopping or reversing the motor, the process happens in reverse, with the high current switching managed by the semiconductors.

The benefit is that due to the electronic switching, the mechanical relays are much smaller as they are only switching off-load. This minimises contact bounce and arcing giving the starters an excellent high vibration rating with built-in output protection. Switching motors using a hybrid system improves contact life by a factor of ten to increase system reliability. Typical starter utilisation categories are AC-53a for use with inductive loads according to IEC 60947.

In addition to monitoring the motor current, the adjustable electronic overloads can also offer protection against phase loss, unbalanced loads and locked or stalled rotor. Hybrid motor starters benefit multi-motor configurations, offering space savings up to 75%, and reducing internal wiring, design and construction time. Popular machinery applications include standard induction motors used for  fans, pumps, hoists, conveyors and production feeding systems.

 

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