Elevator electrical problems - Elevator motor damage

The motor is one of the most vulnerable parts of your elevator system to power issues.  From time to time we have premature motor issues which is difficult to explain and we attribute it to prolonged wear due to power issues.  We did some quick research for reference.

Here are some issues that will prematurely wear your motor

1.    Under/over voltage

a.    Under voltage - Can come from heavy use from your electrical grid/building

b.    Over voltage – When power grid doesn’t respond fast enough to shifting loads or lightening strike.

2.    Phase Loss/reversal  

a.    Can occur from lighting strike, power line issue, blown fuse, wiring error or contactor failure

3.    Voltage imbalance

a.    Contactor fails

b.    Tin can transformer fails and is replaced with a new one

c.    New load is added to one phase of facilities power system

2% imbalance = 8% temperature rise in motor windings

3% imbalance = 18% temperature rise in motor windings

As imbalance grows worse the temperature sky rockets

The higher the temperature the sooner the insulation on the motor windings will fail

NEMA[National Electrical Manufacturers Association] recommends less than 1% imbalance

When I am engineering elevator modernization projects we have started measuring each leg along with leg to leg.  It is rare that we are within the 1% NEMA recommendation on most of the buildings I go to.

What happens to your motor?  All these zips, zaps and drains will take a toll on the motor and lead to premature motor failure.  

What is the solution?

Add a phase monitor – A phase monitor can be installed for less than $1,000.00 and will protect your motor from many of the electrical issues listed above.  There are very simple phase monitors that will turn the elevator off when a power issue is detected. There are also phase monitors that will trap information so you have it and you can use it to pin point electrical issues and you can develop potential solutions.

[This device of a similar device is what we find on most older elevator systems with phase protection - it works great but you get limited information when it detects power problems]

[This device not only tracks phases but it traps a lot of information with time stamps - for a few more dollars you will get a lot more information]

Add a soft start motor starter – This is a device that will not only smooth out your electrical curve but also has phase protection built in.  The soft start will also increase your ride quality when replacing a mechanical motor starter. This device can be installed for $2,500.00 to $5,000.00 dependent on your VAC, HP and where it will fit in the elevator control system. 

Take away – Electrical issues are a buzz word in our industry because most of our issues are attributed to what the power the building supplies the elevator system.  Take a peek at a picture of a very old mercury switch from 50+ years ago that was installed to protect phase reversal, this is an age old problem.  If you are having issues, identify them and address them with your elevator contractor.  There are many tools out there that can help you quickly resolve power issues.  While we are talking about motors in this post, your elevator’s control system will also have significant issues if we do not supply it with the correct power.

[Left is newer phase protection - Right is very old phase protection]

If you have any questions or would like additional information feel free to contact me at CraigZ@colleyelevator.com or 630-766-7230 ext. 107.

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