Modification To Convert Exhaust Brake Switch To Normal "ON"

[HBarlow]

I had never even heard of an electro-magnetic retarder. Live and learn.

 

[JHumphries]

The city buses around Bremerton, WA have the electromagnetic retarders. I would assume other municipalities have them as well.

 

[Bill Stockard]

The city buses around Bremerton, WA have the electromagnetic retarders. I would assume other municipalities have them as well.

Electromagnetic retarders usually require more vehicle battery capacity and larger alternators. When at full retard, they can draw around 450-500 amps electrical load for a short time. Unlike engine brakes, they are quiet and require no engine modifications.



Bill

 

[HBarlow]

Ahhh, now I understand. They are used for the quiet advantage on fire trucks and busses which operate in inner cities.

 

[cojhl2]

Electromagnetic retarders usually require more vehicle battery capacity and larger alternators. When at full retard, they can draw around 450-500 amps electrical load for a short time. Unlike engine brakes, they are quiet and require no engine modifications.



Bill

I've gotta lookup how they work. One would think they would convert kinetic energy to to electric power and not the other way round.

 

[JHumphries]

The electro-magnetic retarders put a generator on the drive line. That generator is connected to a resistive load bank. The diveline becomes and alternator and the resistor bank gets hot. It's like the 'Regerative Braking' on a hybrid. They use vehicle momentum to generate electricity. Instead of charging the battery, the electricity is run to resistors which generate heat. The heat is radiated away. It is almost completely quiet.

 

[Cosmo]

Ahhh, now I understand. They are used for the quiet advantage on fire trucks and busses which operate in inner cities.

Which is funny given that buses and fire trucks are typically the loudest vehicles on the roads, fire trucks especially.

 

[Bill Stockard]

The electro-magnetic retarders put a generator on the drive line. That generator is connected to a resistive load bank. The diveline becomes and alternator and the resistor bank gets hot. It's like the 'Regerative Braking' on a hybrid. They use vehicle momentum to generate electricity. Instead of charging the battery, the electricity is run to resistors which generate heat. The heat is radiated away. It is almost completely quiet.

Not quite... Telma retarders don't generate electricty. Instead the retarder uses electricty from the vehicle's electrical system to create strong magnetic fields with alternating polarities. This is from the Telma web site on how it works:

"Rotating parts called rotors are attached to the driveshaft. Separated by a narrow air gap, the stator is connected to the vehicle chassis. When electricity flows through the stator coils, electromagnetic fields with alternate polarities are created. As the rotors pass through these fields, eddy currents are generated which slow the rotors and thus slow the driveshaft. Any heat generated during braking is self-dissipated through the rotor vanes. "



Bill

 

[JHumphries]

I guess I'm thinking of someone else's.
Telma's turns the driveline into a motor and tries to turn it in the opposite direction to slow the vehicle.

 

[cojhl2]

I guess I'm thinking of someone else's.

Telma's turns the driveline into a motor and tries to turn it in the opposite direction to slow the vehicle.

Regardless,, of the internal process. The point is: there is kinetic energy that has to go somewhere (heat). So why does it take all that energy (Amps)from the vehicle battery when there should be plenty residual left over to excite the stator?

 

[JHumphries]

The vehicle batteries are being used to generate a magnetic field that opposes the rotation of the driveline. That opposition is what slows the vehicle down.