[cricketo]

Folks,

Got this technical question mostly out of curiosity. Say if I were to connect a full bridge rectifier and a capacitor to the household 120VAC, would that be acceptable for running say a 80V (116V max?) Sevcon Gen4 with an appropriate motor and under proper current limits ?

 

[wjbitner]

Folks,

Got this technical question mostly out of curiosity. Say if I were to connect a full bridge rectifier and a capacitor to the household 120VAC, would that be acceptable for running say a 80V (116V max?) Sevcon Gen4 with an appropriate motor and under proper current limits ?

I don't know the limits on a Sevcon 4, but you end up with higher than 120 volts using a full wave bridge and cap. I've seen people do it the Leaf, using a 220 circuit. As long as you keep the current limits low, it will work. (assuming the sevcon can tolerate ~160 volts DC in.)

 

[cricketo]

160VDC is certainly too much for 80V Sevcon, so maybe half wave rectifier would work better.

 

[TeZla]

Would the amperage draw be a problem though?
I know you can 'reasonably' easily get the voltage where you need it but the household circuit still maxes out at 20-30A? That in itself really depends on how the circuit is wired, conductor size etc. Put too much draw on the circuit and you'll trip your breakers, heat up the conductors in the walls, overload the circuit and risk a fire ect ect. The battery acts as a big reservoir of power, a household circuit doesn't have that, its literally power on demand.

I reckon it'd work for turning things on, but I personally wouldn't try to spin up a motor. Be careful and be safe.

 

[cricketo]

Would the amperage draw be a problem though?
I know you can 'reasonably' easily get the voltage where you need it but the household circuit still maxes out at 20-30A? That in itself really depends on how the circuit is wired, conductor size etc. Put too much draw on the circuit and you'll trip your breakers, heat up the conductors in the walls, overload the circuit and risk a fire ect ect. The battery acts as a big reservoir of power, a household circuit doesn't have that, its literally power on demand.

I reckon it'd work for turning things on, but I personally wouldn't try to spin up a motor. Be careful and be safe.

Correct, most common 120VAC outlets are limited to 15A in the US, and some are setup for 20A. Sometimes it's possible to pull 30A from a dryer or 50A from a range outlet (one leg of the split phase plus neutral), but I was under impression neutral can be downrated in those circuits, not absolutely sure, would need to verify if it comes to that.

I do quite a bit of custom electrical setups for my projects, so technically I can get as much as my service will allow - 200A. Primary context for the question was around bench-testing 100VDC drivetrains, like when it's not practical to have a battery for them nearby. Without load it's unlikely most motors pull more than 20-30A. Secondary thought was use of such components in machining equipment.

 

[wjbitner]

160VDC is certainly too much for 80V Sevcon, so maybe half wave rectifier would work better.

No, the 1/2 wave would still have the peak voltage, but only 1/2 the current. I'd get a VARIAC, auto transformer. Something like this

Anesty Variable Auto Transformers Adjustable Voltage Transformers 5Amp 0-130V: Amazon.com: Industrial & Scientific

Anesty Variable Auto Transformers Adjustable Voltage Transformers 5Amp 0-130V: Amazon.com: Industrial & Scientific

www.google.com

That way you, you can ramp the voltage slowly, to charge up the capacitors in the Sevcon and your filter cap. I wouldn't worry too much about the current, but I would
ramp the motor slowly and wouldn't have any load on the motor. Free spinning only. Here's someone spinning a much higher voltage Nissan Leaf motor on house voltage

Bill

 

[cricketo]

No, the 1/2 wave would still have the peak voltage, but only 1/2 the current. I'd get a VARIAC, auto transformer. Something like this

Anesty Variable Auto Transformers Adjustable Voltage Transformers 5Amp 0-130V: Amazon.com: Industrial & Scientific

Anesty Variable Auto Transformers Adjustable Voltage Transformers 5Amp 0-130V: Amazon.com: Industrial & Scientific

www.google.com

That way you, you can ramp the voltage slowly, to charge up the capacitors in the Sevcon and your filter cap. I wouldn't worry too much about the current, but I would
ramp the motor slowly and wouldn't have any load on the motor. Free spinning only. Here's someone spinning a much higher voltage Nissan Leaf motor on house voltage

Bill

Isn't it the idea behind the PWM though ? Even though peak may exceed the rated voltage, under load the voltage will drop right away as long as the pulse width doesn't exceed a certain value ? Certainly AC input offers some flexibility due to possible use of transformers, I was thinking more alone the lines of "keep it simple" and "reduce the number of components."

 

[wjbitner]

Isn't it the idea behind the PWM though ? Even though peak may exceed the rated voltage, under load the voltage will drop right away as long as the pulse width doesn't exceed a certain value ? Certainly AC input offers some flexibility due to possible use of transformers, I was thinking more alone the lines of "keep it simple" and "reduce the number of components."

In theory yes.. However, a regulator that uses PWM also has a sense circuit and feedback loop to keep the voltage where you want it. Many more parts and $.. A variac is old school and simple..