Good point there Mike.
We've been producing AC reachtrucks for 6 years now and not had too many problems and the same goes for the AC power pallet trucks we've had out there for a couple of years now..... so you've probably not got much to worry about.
There is 1 huge advantage to AC that no one has pointed out yet...
100% torque is availible 100% of the time.
The torque does not drop off as speed increases. You get higher loaded travel speeds without having to use huge inefficient motors.
The NACCO lineup was supposed to be 100% AC by Jan 06, but that's been pushed back till June 06.
All we have right now is the 3 and 4 wheel sit downs and the 3 wheel stand up (HSD)
We will also be transitioning over to Inmotion controls supposedly.
Our new AC narrow isle trucks look pretty, but I'll reserve judgement until they are actually running around.
Toyota introduced AC drive to the US market in June 2000 to Class 1.
That would be 5 full years and some change......
NACCO - North American Coal corporation = NMHG = NACCO Material Handling Group = Hyster plus Yale
Introduced AC Class 1 Nov-Dec 2003
And the flip side
Crown...still using EV100 panel (giggle)
Some right and wrong comments in the above.
AC controllers do certainly run hotter than DC due to the amount of FETS that are being switched and the frequency that they are switched, both of which are substantially higher than DC units.
Power consumption is less than that of DC........The reason for the stated 3% is that AC machines are generally more powerful in terms of speed and torque compared to a DC units, so if an AC unit was de-rated the power saving would be higher.
AC power is superior to DC because the motors are more controllable, powerful and cheaper in the long run due to the reduction in parts, especially for the motors.....just think no looking at another raised comm bar from an operator bulldozing a load!
In Europe we are manufacturing 36V (For the US market), 48V, 72V (Not so much these days) and 80V units, and the technology has been used in Lift Trucks for 3 - 4 years here already.
ac is an advantage,"less moving parts,less heat,heat is energy
There are a few drawbacks of an AC compared to a DC powered lift. First, the AC motor controller will heat up faster and cut back the power to the motor if the lift truck is used to push loads or climb a lot of ramps. The second thning is that the AC motors are new to lift trucks, at least in the US. Replacement motors and motor controllers will be more expensive than convetional DC motors. The third thing is the the power consuption of a AC truck is only about 3% less than a comparable DC truck.
The AC trucks I have seen do not have enclosed motors and Many DC motor trucks are now pwered by MOFSETS.
I can see a definate advantage to having an AC motor in an explosion proof truck. All DC motors produce sparks at the brushes. The AC motors do not.
I assume the above minor drawbacks of the AC motor powered lift trucks will be overcome and the AC motor will be much more common.
In the US, the common battery voltage is 36 or 48 volts. Euerope is 72 to 80 volts. The heat problem with the motor controller I mentioned may not be a factor in Europe. I'm all for not having to replace those nasty black carbon brushes.
In addition to Benny's and Fred's replies, the AC motor is totally enclosed and will resist to dust and humidity much better. Added to that is the fact that AC motors are unusally controled by high efficiency Transistor controlers (MOSFETS) which are energy misers. You can add that the controlers for AC motors are more versatile in the programing capabilities.