Regen braking with a "backup" snubber braking

Dan: Just use an open loop control method on the vfd. The encoder feedback is only useful for tight speed regulation, or for holding torque at low/zero speed. In this application it is just another part to fail.

The 'braking torque' when you let off the gas pedal can be adjusted via a Regen or Braking torque parameter...
 
Dan,
When you lift on an ordinary car it coasts with some engine compression braking.
Fork lifts are designed to get one shift out of a battery. When the operator lifts on a lift truck dynamic braking kicks in and that inertial energy is sent to the battery. Slowing can best be described as severe. Lifting your foot is almost like hard braking.
I have driven a Prius and that is programmed to regen but coast like an ordinary car.
See if you can find a 10 year old or newer 48 volt truck and ask if you can drive it. In 20 feet you will see exactly what I an describing.
The S10 conversion is different from a car in that it slows quickly after lifting, surprising both the driver and the car following. Often the foot brake is only used to hold the truck on a hill at a light. It took some fiddling to get the brake lights to come on when in regen.
Also when he floors it he surprises the hell out of everyone. Nothing beats DC torque and the battery in the back limits wheel spin.
 
Dan,
When you lift on an ordinary car it coasts with some engine compression braking.
Fork lifts are designed to get one shift out of a battery. When the operator lifts on a lift truck dynamic braking kicks in and that inertial energy is sent to the battery. Slowing can best be described as severe. Lifting your foot is almost like hard braking.
I have driven a Prius and that is programmed to regen but coast like an ordinary car.
See if you can find a 10 year old or newer 48 volt truck and ask if you can drive it. In 20 feet you will see exactly what I an describing.
The S10 conversion is different from a car in that it slows quickly after lifting, surprising both the driver and the car following. Often the foot brake is only used to hold the truck on a hill at a light. It took some fiddling to get the brake lights to come on when in regen.
Also when he floors it he surprises the hell out of everyone. Nothing beats DC torque and the battery in the back limits wheel spin.
Have driven forklift since 73. DC and then AC up to 6,000 lb capacity.
 
Have driven forklift since 73. DC and then AC up to 6,000 lb capacity.
I still think that very-very long preset for the deceleration time will be almost like car's motor braking at normal gear. Of course you can connect switch to the brake, or change to shorter decel time by switch at full lifting of your foot from the gas pedal(upper limit switch)In normal conditions you should run away from the braking resistors in order to save battery.
 
Dan,
When you lift on an ordinary car it coasts with some engine compression braking.
Fork lifts are designed to get one shift out of a battery. When the operator lifts on a lift truck dynamic braking kicks in and that inertial energy is sent to the battery. Slowing can best be described as severe. Lifting your foot is almost like hard braking.
I have driven a Prius and that is programmed to regen but coast like an ordinary car.
See if you can find a 10 year old or newer 48 volt truck and ask if you can drive it. In 20 feet you will see exactly what I an describing.
The S10 conversion is different from a car in that it slows quickly after lifting, surprising both the driver and the car following. Often the foot brake is only used to hold the truck on a hill at a light. It took some fiddling to get the brake lights to come on when in regen.
Also when he floors it he surprises the hell out of everyone. Nothing beats DC torque and the battery in the back limits wheel spin.

Have driven forklift since 73. DC and then AC up to 6,000 lb capacity. Dynamic braking either AC drive or DC drive did not result in load sliding off forks. Panic braking did sometimes. Have no doubt I value dynamic braking.

I started studying electric drive in vehicles in 07 or thereabouts.
Have seen many small pickups with electric drive. Those done by owner using DC series motor lack torque at higher end ie 60 mph and for hill climbing they must have transmission - seems to me these motors are undersized. Every one I have checked after driving in Seattle seemed overheated to me. I did DC maintenance on Navy submarine and got my fill of it. I considered using forklift AC drive system in truck until I found that factory would not share information - and a forklift repair guy recommended against salvaging forklift motors due to inadequate HP - he is owner of White Zombie - took care of that idea.

So now my concept is to choose the motor that is correctly sized to meet the demands of the load.
1. KNOW THY LOAD measure torque needed to roll vehicle using torque wrench.
2. Calculate driveline speed and torque demand based on 1
3. Pick motor based on 2

So on 56 Chev pickup I did the above. THe motor was purchased from Boeing Surplus for $229 Leeson 3600 RPM 50 HP. Direct couple to driveline - no transmission. DICK DV and another advocate using 1800 RPM motor and I see their point and agree with it. Would give better starting torque for sure and more than enough torque thru baseline and up to about
2600 RPM where torque is just under 70 ft lb - corresponds to 58 mph
2800 RPM 60 ft lb and about 63 mph.
HOWEVER - this does not include windage which is nearly negligible at 35 mph or less but is a square function of relative velocity. I do not have a wind tunnel and I am sure I am unable to talk my neighbor (Boeing) into loaning me one to measure wind resistance and thus derive torque demand of wind resistance at speeds 40 thru 60. This evaluation will be done by road testing.

SO for now I am going to stay with the 3600 RPM motor for several reasons
1. I have it, brand new, low cost, should have adequate starting torque (other than very steep hills ie 15 or 20%) and it should meet my needs from 0 to 60 mph.
2. It will make a good pilot program motor and will give me good measurements to make the final decision to stay with 3600 RPM or switch to 1800 or maybe even 1200 RPM motor.
 
Dan: Just use an open loop control method on the vfd. The encoder feedback is only useful for tight speed regulation, or for holding torque at low/zero speed. In this application it is just another part to fail.

The 'braking torque' when you let off the gas pedal can be adjusted via a Regen or Braking torque parameter...

Yes I know accel and decel ramps can be adjusted. Have small model car driven with either of two VFDs - 1/4 and 1/2 HP motor is 100 watt. Circa 1985 GE VFDs both planar. Use in classes to demonstrate different accel and decel rates, operating on flat floor or on a 30% slope under varying loads up to approx 60 lbs. Way overgeared I know at approx 42:1 but that is intentional to keep speed slow in classrooms.

I am thinking that on hills and on freeway in rush hour with vector drive and motor at low RPM I will need fairly precise speed signal and will need foward and reverse signals to enable the VFD to do catch on fly ie match VFD output to that of "idling" motor. This will be finally decided by the VFD manual and manufacturer.

I am trying to avoid last minutes uh ohs - and I forgots. Most important is gain knowledge from those who have used particular brands of equipment in real world field application and have had good service from the component ie 5 years or more.

Dan Bentler
 
Dan,
I was mistaken, it is a Toyota AC drive, not DC.
I have 2 customers that have plastic pallets forced upon them by customer requirements. They have continuing damage problems because of the plastic sliding off the forks. The trucks travel at speed in the warehouse and when the driver slows a small amount the skid slides off. That did not happen with the old propane trucks. They use this same Toyota AC truck.
You are correct, the fork truck motor is undersized. It works very well for a 15 mile trip to work on relatively flat roads. 55 mph is it and there is no heat or air.
The Drive parts were "obtained" by a friend in that business. He hasn't tried to max out the truck because of the very heating issues you describe.
It was a fun project and fairly cheap. $1000 for the truck and $500 for odds and ends.
It is a long way from a Prius but has paid for itself (not counting labor) already with gas at almost 4 bucks a gallon.
 
I have decided (uh oh ??) Will go vector drive

There will be no external device to detect motor speed or other mechanical parameters. I will go "open loop" also called sensorless.

Yaskawa F 7 60 HP drive has been recommended. Read factory manual, that looks good.

Who has in field experience with these, and for how long? What should I look out for or be very careful about.

Having difficulty getting local ABB rep returning email and voice mail.

Who in Seattle area would like my business?
 
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Set the drive control mode for sensorless vector and you won't need any of those. Even for a speedometer, the analog output from the drive would be accurate enough.

I think the point about letting off the accelerator is that, unless greatly softened somehow, the AC drive will take the motor to full regen braking when you let up. That would be unexpected if comparing to a gas engine where a little braking but only a little is expected.
 
Set the drive control mode for sensorless vector and you won't need any of those. Even for a speedometer, the analog output from the drive would be accurate enough.

I think the point about letting off the accelerator is that, unless greatly softened somehow, the AC drive will take the motor to full regen braking when you let up. That would be unexpected if comparing to a gas engine where a little braking but only a little is expected.

Dick DV

Gas engines are a bit mushy on braking when compared to electric drive.
I fully agree and am concerned on downhill with snow and sometimes ice in Seattle. With a decel ramp set I think it would be "fine tuned" with a sensitive foot on throttle ie back off to 75% speed command and you get the same decel rate ie dRPM/dT but the effect ie traction loss skid potential would be less I think than if you backed off to 50 or 25%.

With my model unit I can get it to skid if start braking on a sheet of ABS. That is done with a very steep decel ramp - with a moderate decel ramp it is not as bad. I dream of a switch to select acel and decel ramps ie "dry road" vs "snow n ice".

Dan Bentler
 
Dan: I was referring to the current/torque limit adjustment for the braking/regen...

It's different than the speed ramp. You typically set in in % of full rated torque, so you can fine tune the action of the braking when lifting the gas.

The F7 is a fine drive. It is a generation out of date, so if you can find one, go for it. It's reliability is better than the new design from what I've seen.

You've got a good plan, and the right attitude to succeed!
 
Dick DV

Gas engines are a bit mushy on braking when compared to electric drive.
I fully agree and am concerned on downhill with snow and sometimes ice in Seattle. With a decel ramp set I think it would be "fine tuned" with a sensitive foot on throttle ie back off to 75% speed command and you get the same decel rate ie dRPM/dT but the effect ie traction loss skid potential would be less I think than if you backed off to 50 or 25%.

With my model unit I can get it to skid if start braking on a sheet of ABS. That is done with a very steep decel ramp - with a moderate decel ramp it is not as bad. I dream of a switch to select acel and decel ramps ie "dry road" vs "snow n ice".

Dan Bentler

Dan,
Are you really going to drive that truck in those conditions if it doesn't have a heater?
 
Gene
Thank you for the encouragement - kind of discouraging day today. Will ;have to study up on the torque limit setting in whatever VFD I end up with.

Gas
Yes I will drive it in these conditions
WITH electric heated seat AND insulated coveralls BETTER YET heated and insulated coveralls. Thinking of placing VFD in cab to take advantage of waste heat estimated at 2kW for 50 to 60 HP drive. Other electronics will go in cab mostly to keep them out of Seattle rain. Braking resistor if used will go in cab. Now then where do I fit in - good thing I have submarine experience - smallest electrician - amazing where they could cram me.

Dan Bentler
 
Cool,
Keep us posted on the progress.
General Electric here in Erie makes locomotives. In the late 60s and early 70s they also made an all electric garden tractor with mower and snow blower. Not many were sold and I haven't been able to find any restoreable ones. They were quiet and safe and would easily run all afternoon.
With today's "green" focus someone should start making these again.
 
GE's Etrak was a pretty good machine - know a guy who has one. Not sure about them running all afternoon - motor speed control was done with resistors.

John Deere I think has several models of electric "home tractors"
Will post updates.

Dan Bentler
 

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