Explaining the IP Ratings of Variable Speed Drives?

As you know at Quantum Controls we regularly post information from our clients who have asked us specific questions relating to their Motors or Drives.  This time we have received a number of queries concerning the ‘IP Ratings of Variable Speed Drives’.

IP00, IP21, IP54 and IP66 are now all available for ABB drives, but which one should you use?

IP means “ingress protection”, in which a higher number denotes higher protection, so it is easy to assume that the highest number available will offer the best protection. Installers may even be under the impression that the location does not matter as the drive is so well protected, but to assume so is incorrect.

A high IP rating will protect against water jets or water splashing, but drives fitted outdoors are normally located on rooftops, typically controlling air handling units, where splashing water is not usually a problem.  Instead, it is the moisture in the air, sealed inside the drive enclosure that has the potential to damage the drive electronics.

The IP rating of the drive has no effect on the air drawn in by the unit’s cooling fan and, in fact, can a cooling fan operate properly against water jets?  If damp air circulates inside the drive enclosure and the internal heat sink cools down enough for the temperature to drop below the dew point, condensation will form, which could damage the electronics. It is important to remember that IP numbers do have specific meanings.

The first digit denotes protection against solid objects and the second against liquids. For an IP66, for instance, number 6 in the first position means “totally protected against dust ingress” and in the second position “protected against high pressure water jets from any direction” – not a particularly relevant feature in a rooftop location.

Quantum has designed an IP66 enclosure system with our ABB Drives. Ranging from 1.5kW – 400kW so if your switch rooms are full to bursting point we have a ready-made solution suitable for mounting directly in to your plant our even outside.

These units are available for sale or to hire and have provided an ideal solution to many of our clients limited space problems when installing new machinery, or simply wanting to upgrade existing Direct on Line (DOL) starters to VSD control for process improvement and energy saving.

Question

When should I use Variable Speed Drive control for my motor?

Answer

To understand why variable speed drive control is required, we first need to understand the requirements of different processes. These processes can be divided into two main categories, material treatment and material transport, although there are many different sub-categories that come under these two basic headings.

Common to both categories however, is the need to be able to adjust the process, through control of the motor speed? So if you need to control and or vary the speed of your motor then a VSD is the correct motor starter option.

Question

What are Bearing Currents caused by Variable Speed Drives

Answer

Some new drive installations can have their bearings fail only a few months after start up. Failure can be caused by circulated high frequency currents, which flow through the motor bearings. While bearing currents have been around since the advent of electric motors, the incidence of damage they cause has increased with the popularity of VSD’s as they are the modern preferred motor control method.

This is because modern drives with their fast rising voltage pulses and high switching frequencies, can cause current pulses through the bearings whose repeated discharging can gradually erode the bearing races and lead to premature motor failure.

To find out more information regarding  sale or hire options we have available for our IP66 enclosure system with our ABB Drives for your plant, please do not hesitate to contact us on 0330 9000 247 and we will be delighted to help you. 

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