I found a few more photos of antique elevators plus some 1950's vintage equipment.

The motor arrangement shown in the 3rd picture is known as a "Micro Drive" unit in which the main motor was used for running at high speed between floors. Then the smaller motor and gear reduction and clutch/brake on the left side was connected to the main motor during final stopping at the floor level. The 4th picture is an actual micro drive installation that is still in operation someplace in the U.S.

The 5th picture is a 1950's vintage elevator machine with a DC variable speed drive. The motor generator unit on the left side of the machine converted the 3 phase power to variable DC.

 

I posted this before, but another interesting motor of that era and in some cases is only just being phased out in some locations, namely the Induction start synchronous motor often around 100hp driving huge single cyl compressors and pumps.
The motor is ran up to min slip as an induction motor, the winding on the rotor has two slip rings where the slip is detected, at around 6 cycles slip, DC is injected into the rotor and the motor comes up to synch.
Max.

 

I've found some more photos of relics that are still running and in good condition.

The first photo is an 1926 vintage geared machine made by Westbrook Elevators Inc. that's been upgraded by adding an inverter of some type. There is a tachometer on the rear bearing.

The second one is another geared machine made by Old American Elevator Inc. which may have been made over 80 years ago. It also looks like an old AC motor that's been upgraded to an inverter with tacho feedback. I believe these antiquated motors must use some variation on a bipolar transistor inverter (such as SCRs or GTOs) instead of the modern IGBT type. An IGBT inverter would eventually pop the insulation on these older motors.

The last photo is an Otis "gearless" machine where the cable sheave is directly mounted to a permanent magnet synchronous motor.

 

Are you sure they are Tacho's? Often in these applications, it was desirable to ensure motor had stopped before reversing, a variable reluctance type zero-speed switch was often fitted.
Max.

 

The sensor on the1926 AC motor looks like an encoder which was used on the so called "vector" drives for an induction motor.

The encoder provides angular position of the rotor and the inverter can adjust the angle of the flux in the stator (both the magnitude and direction) in order to maximize torque and speed accuracy. Vector control is greatly superior to plain slip control and vector control is the standard for elevator drives.

The tachometer on the blue machines looks like a pulse generator made by Weston Electric. That's a DC motor which can use a simple tachometer to provide feedback for an SCR drive.

However, these days, it's unusual to find old fashioned motors that have been retrofitted with electronic drives. I suspect these motors were retrofitted back in the late 1970s or 80s when modernizing older elevators was done by highly skilled artisans who knew how to "Blend the old with the new". There is a company in New York called "GAL" that is regarded as one of the world's leading authority on retrofitting old fashioned AC or DC elevator motors with solid state drives and the company has modernized 1000s of elevators dating back to the 1900s.

Today, however the strategy is just to rip out everything and start over from scratch.

 

What were the advantages of switching to 60 Hz then?

Which begs the question, why not a higher frequency than 60 Hz then?

I'm guessing that the answer lies in the number of windings needed in a generator... which would in turn make it more expensive to fabricate

So the 30Hz version of a motor would be even more efficient?

My question is directed at: what would be the perfect frequency for today's industry, if standards were to be redefined?

Ok here's my condensed understanding of why we standardized on 60hz and not something else.. (guaranteed inaccuracy to some degree- self study recommended)...

In the beginning... we were limited to 60Hz because we did not have technology and metallurgy to create magnetic cores with reluctance low enough to support a higher frequency. Well, we probably could have gone higher with more money invested into mining and mixing better metals to better standards but there was probably a point of diminishing returns, which apparently was somewhere around 60Hz.

Fast forward to today, our technology is much more advanced and if we worked out what our new point of diminishing returns is, I would bet that it is (or could be) 400Hz or higher, maybe into the kHz range. But it would be too disruptive to change it at this point.

For a developing nation that doesn't already have widespread electrical infrastructure, I would recommend standardizing on HVDC. If not that, then kHz AC. But please, don't choose 60Hz just because that's what we did. Do it better.


Edit: ....aaaaand I just realized those quotes were a year old.

 

I ran across a couple of photos of Westinghouse gearless traction motors.


The first photo shows the sheave for the cables which is mounted directly on the armature shaft, hence the term "gearless". The brake drum is right behind the sheave and the brake shoes are released by a large solenoid and applied by springs.

The second photo is the commutator end of the same motor. I suspect these motors were made in the 1920s or 30s.

 

These are modern state of the art gearless traction elevator motors in the "Freedom Tower" in Manhattan.

They are permanent magnet synchronous motors and the rotor contains several hundred pounds of rare earth magnets. The elevators are "double deckers" which have an upper and lower cabin within a single car frame and the total capacity is 10,000 lbs. Because of the unusually high capacity and very large total moving mass, the maximum starting torque is about 60,000 Ft.-Lbs.

 

Here are two photos of the Otis Model 339 HT gearless machine which is the largest DC elevator motor ever built.

The first is for one of the two elevators in Stratosphere Tower in Las Vegas which has a capacity of 10,000 Lbs. at 1700 feet per minute. The second is the wreckage of a 339 HT motor from the elevators in the WTC Towers. I believe there were 25 of these motors in each tower.

 

Here are two photos of the Otis Model 339 HT gearless machine which is the largest DC elevator motor ever built.

The first is for one of the two elevators in Stratosphere Tower in Las Vegas which has a capacity of 10,000 Lbs. at 1700 feet per minute. The second is the wreckage of a 339 HT motor from the elevators in the WTC Towers. I believe there were 25 of these motors in each tower.

View attachment 142723 View attachment 142724

What are the smaller coils between the large ones for? Brakes?

 

What are the smaller coils between the large ones for? Brakes?

The smaller coils are called "Interpoles" which minimize the shift of the field of the stator field due to armature reaction.

When the motor is in dynamic braking mode, the armature field is either attracting or repelling the field flux which results in distortion of the field itself.

 

This is a video of the WTC elevator motors:

The tall machine with the rotating cams is called the "floor selector" which replicates the actual movement of the elevator car. Over 1000 feet of travel of the elevator car is replicated in the floor selector which is about 10 feet tall.

 

I ran across an ad for used surplus electrical and mechanical equipment which shows a 1971 vintage Haughton gearless traction elevator motor. This is a very large DC motor and viewed from the commutator end. The cable sheave and the brake are on the right side.

This motor was used on a 7000 Lb. capacity elevator and the cables went through a sheave on the car and counterweight to give a 2;1 lifting advantage. The second photo is also another Haughton gearless motor that's still in service. The third photo is an Otis Model 339 HT gearless motor which is used in buildings over 1000 feet and elevator capacity of 8000 to 10,000 Lbs. Only a few buildings in the world use motors this size and I'm guessing they are installed in the Petronas Towers in Malaysia.

I've added a couple of photos of a 339 HT motor in the Stratosphere Tower in Las Vegas.

 

This motor was used on a 7000 Lb. capacity elevator and the cables went through a sheave on the car and counterweight to give a 2;1 lifting advantage

Counterweight....
I knew elevators had a counterweight, but until you mentioned "lifting advantage" (and I'm not even sure this is what you meant), I never considered how much the counterweight weighs relative to the empty elevator. I consulted all-knowing...

https://www.explainthatstuff.com/how-elevators-work.html
The elevator car is balanced by a heavy counterweight that weighs roughly the same amount as the car when it's loaded half-full (in other words, the weight of the car itself plus 40–50 percent of the total weight it can carry).

So all the movies, all the nightmares, all the urban legends, they got it wrong. If you were alone on an elevator (or even with a few friends) and the motor/brake failed, you wouldn't go falling toward the earth, you would go hurtling up at the sky, slam into hard stops at the top of travel, and be thrown into the ceiling possibly at terminal velocity. At which point maybe the cable would break, and then you would fall to your 2nd death at the bottom of the shaft.

 

Counterweight....
I knew elevators had a counterweight, but until you mentioned "lifting advantage" (and I'm not even sure this is what you meant), I never considered how much the counterweight weighs relative to the empty elevator. I consulted all-knowing...


So all the movies, all the nightmares, all the urban legends, they got it wrong. If you were alone on an elevator (or even with a few friends) and the motor/brake failed, you wouldn't go falling toward the earth, you would go hurtling up at the sky, slam into hard stops at the top of travel, and be thrown into the ceiling possibly at terminal velocity. At which point maybe the cable would break, and then you would fall to your 2nd death at the bottom of the shaft.

There have been several incidents where the friction brake on the traction motor (the drum next to the cable sheave) failed to apply and the counterweight pulled the car upward. In one bizarre incident, all the bolts that attached the gear (on the shaft that drives the cable sheave) broke and allowed the counterweight to run away in the UP direction. The cause of the accident was determined to be negligence on the part of the maintenance company which never inspected any of the components inside the gear case.

However the total mass of the car, counterweight, and cables was so large that the velocity wasn't anywhere near a free fall condition. The "Atwood's Machine" shown in physics books is a simple example of an elevator where two masses are suspended on a cord that runs over a pulley at the top.

As double insurance, some states now require a "rope brake" which has parallel grooves that gently grip the cables that go to the counterweight.