It's cool to keep motors protected

Edited by the Engineeringtalk editorial team Feb 26, 2004

Reliable refrigeration is crucial to the dairy industry - downtime on a refrigeration unit means lost production.

Reliable refrigeration is crucial to the dairy industry - downtime on a refrigeration unit means lost production.

With this in mind, a major dairy turned to Grenco Refrigeration for a new chilling system.

For control and protection it incorporates a motor control panel from ICA Electrical, with Moeller Electric's ZEV electronic motor protective relay at the heart of the motor protection.

Grenco Refrigeration's 1MW chiller provides chilled water for the dairy.

Four 315kW motors are used for each compressor, with the number running at any one-time being dependent on the demand for chilled water - one motor is available as a reserve.

The motors are critical items, as any downtime on their part would adversely effect production.

Reliable switching and protection of these motors is an absolute necessity.

ICA Electrical's electrical director, Ian Thorne, sets the scene: "Conventional thermal overload relays would not provide an adequate level of protection for motors of this size.

Moeller's ZEV offers us better protection, and more detailed information on fault monitoring and reporting".

Moeller's ZEV, awarded the electrical industry's prestigious Innovative Product of the Year Award in 2001, is an ultracompact, flexible electronic motor protection system, ideal for motors across a wide range of currents.

Employing the very latest sensor and transformer technology, the ZEV has three parts, the relay, the connecting cables and the sensor.

The relay is common across all ratings, as are the cables (available in 200, 400 or 800mm).

The sensors are selected according to the rating required and cover the entire current range from 1-820A.

Of particular interest is the transformer for the 145 to 820A range, which employs Rogowski coil technology.

As well as being easy to install, this allows the ZEV range to accurately monitor currents - resulting in a high degree of accuracy at all times.

This was used by ICA to match the motor protection requirements of the motors.

Other important features that appealed to ICA were the ZEV's comprehensive motor circuit status reporting system and easy set-up.

The ZEV's front panel provides users with an easy-to-operate interface, with an LCD providing details of all the system's functions, operating states and settings.

Up/down buttons allow currents to be set as well as change tripping classes or auxiliary contact functions.

The reset/test button can be used to reset the device after tripping or to activate a test function.

The ZEV provides sophisticated differential signalling of compressor motor status.

The customer-configurable auxiliary contact function allows different parameters to be used to signal overload, early warning of overload, earth fault or thermistor tripping.

The display of the three phase symbols L1, L2 and L3 allows the faulty phase to be identified quickly when faults occur and, in the event of a fault, the LCD shows the instigating parameter.

Even the most severe of starting situations for the compressor motors can be dealt with by the ZEV motor protective system.

Its enhanced tripping classes allow motors with starting times of up to 40s to be safely protected.

Protection is optimally set by preselecting one of the eight tripping classes between 5 and 40.