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For those running 48V 8-20kW systems, what are you doing for fuse protection on your battery bank?? Brands and sizes??? My 12kW motor has a constant capacity of 250 amps.? The peak capacity is 600.? I don't know what I might actually see for short duration peaks but I was thinking a 300 amp fuse might blow in normal operating if I had a momentary peak on the motor draw.?? What are others using?? Dan Pfeiffer
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NEC generally calls for 175% of Full Load Ampere rating for dual element time delay fuses for motors.? Fast acting fuses, inverse time or instantaneous breakers are all rated differently for the short circuit protection.
However, this only covers short circuit protection, and not an overload condition. Thermal or electronic 'overloads' located after the control circuit directly before the wires to the motor is the generally accepted practice for protecting against an overloaded motor. Fishing line or seaweed maybe binding the shaft and preventing it from spinning freely, for instance.? Or prop stuck in the mud.? This is in addition to the fuses.? Depending on the motor's service factor and temperature rise specs, the overloads usually shut off at no more than 115% or 125% of the FLA.
Overloads have a much tighter current limit range, but they're somewhat slower acting to allow for inrush at startup. (fuses and breakers often vary widely in the actual trip current)? They're meant to recreate the motor's windings' temperature to trip the control circuit.? Also, they're resettable.
See Article 430 of the NEC for more info.
On Thursday, May 27, 2021, 12:39:03 PM CDT, Dan Pfeiffer <dan@...> wrote:
For those running 48V 8-20kW systems, what are you doing for fuse protection on your battery bank?? Brands and sizes??? My 12kW motor has a constant capacity of 250 amps.? The peak capacity is 600.? I don't know what I might actually see for short duration peaks but I was thinking a 300 amp fuse might blow in normal operating if I had a momentary peak on the motor draw.?? What are others using??
Dan Pfeiffer
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Very useful info.? Thanks.?
Does a controller (like the Sevcon4) handle current limiting to the motor??? It does have thermal overload control which is related.? Would the "overleads" device you describe between the controller and motor (sounds like a circuit breaker) be redundant if the controller can do the same thing? ??
Dan Pfeiffer
?
toggle quoted message
Show quoted text
On 2021-05-27 1:56 pm, Dave Yamakuchi via groups.io wrote:
?
NEC generally calls for 175% of Full Load Ampere rating for dual element time delay fuses for motors.? Fast acting fuses, inverse time or instantaneous breakers are all rated differently for the short circuit protection.
?
However, this only covers short circuit protection, and not an overload condition. Thermal or electronic 'overloads' located after the control circuit directly before the wires to the motor is the generally accepted practice for protecting against an overloaded motor. Fishing line or seaweed maybe binding the shaft and preventing it from spinning freely, for instance.? Or prop stuck in the mud.? This is in addition to the fuses.? Depending on the motor's service factor and temperature rise specs, the overloads usually shut off at no more than 115% or 125% of the FLA.
?
Overloads have a much tighter current limit range, but they're somewhat slower acting to allow for inrush at startup. (fuses and breakers often vary widely in the actual trip current)? They're meant to recreate the motor's windings' temperature to trip the control circuit.? Also, they're resettable.
?
See Article 430 of the NEC for more info.
?
On Thursday, May 27, 2021, 12:39:03 PM CDT, Dan Pfeiffer <dan@...> wrote:
?
?
For those running 48V 8-20kW systems, what are you doing for fuse protection on your battery bank?? Brands and sizes??? My 12kW motor has a constant capacity of 250 amps.? The peak capacity is 600.? I don't know what I might actually see for short duration peaks but I was thinking a 300 amp fuse might blow in normal operating if I had a momentary peak on the motor draw.?? What are others using??
Dan Pfeiffer
?
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It would still be really nice to have a breaker right at the battery to protect in the event of a short somewhere along the line.
Looks like Amazon has 48V breakers up to 300A.? I saw a fuse for 500A or 600A, but they're only rated to 32V.??
John
On Thursday, May 27, 2021, 03:43:31 PM CDT, Dan Pfeiffer <dan@...> wrote:
Very useful info.? Thanks.?
Does a controller (like the Sevcon4) handle current limiting to the motor??? It does have thermal overload control which is related.? Would the "overleads" device you describe between the controller and motor (sounds like a circuit breaker) be redundant if the controller can do the same thing? ??
Dan Pfeiffer
?
On 2021-05-27 1:56 pm, Dave Yamakuchi via groups.io wrote:
?
NEC generally calls for 175% of Full Load Ampere rating for dual element time delay fuses for motors.? Fast acting fuses, inverse time or instantaneous breakers are all rated differently for the short circuit protection.
?
However, this only covers short circuit protection, and not an overload condition. Thermal or electronic 'overloads' located after the control circuit directly before the wires to the motor is the generally accepted practice for protecting against an overloaded motor. Fishing line or seaweed maybe binding the shaft and preventing it from spinning freely, for instance.? Or prop stuck in the mud.? This is in addition to the fuses.? Depending on the motor's service factor and temperature rise specs, the overloads usually shut off at no more than 115% or 125% of the FLA.
?
Overloads have a much tighter current limit range, but they're somewhat slower acting to allow for inrush at startup. (fuses and breakers often vary widely in the actual trip current)? They're meant to recreate the motor's windings' temperature to trip the control circuit.? Also, they're resettable.
?
See Article 430 of the NEC for more info.
?
On Thursday, May 27, 2021, 12:39:03 PM CDT, Dan Pfeiffer <dan@...> wrote:
?
?
For those running 48V 8-20kW systems, what are you doing for fuse protection on your battery bank?? Brands and sizes??? My 12kW motor has a constant capacity of 250 amps.? The peak capacity is 600.? I don't know what I might actually see for short duration peaks but I was thinking a 300 amp fuse might blow in normal operating if I had a momentary peak on the motor draw.?? What are others using??
Dan Pfeiffer
?
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I bought my fuses from from ev-west. Thunderstruck didn’t carry them at high voltages. (I’m at 600 Amps at 154V.)
Basically, I looked at the fuses from car EV conversions. They aren’t cheap and they’re big. But finding a variety is no issue.?
Great info on this thread!!! ?Thanks everyone.?
toggle quoted message
Show quoted text
It would still be really nice to have a breaker right at the battery to protect in the event of a short somewhere along the line.
Looks like Amazon has 48V breakers up to 300A.? I saw a fuse for 500A or 600A, but they're only rated to 32V.??
John
On Thursday, May 27, 2021, 03:43:31 PM CDT, Dan Pfeiffer < dan@...> wrote:
Very useful info.? Thanks.?
Does a controller (like the Sevcon4) handle current limiting to the motor??? It does have thermal overload control which is related.? Would the "overleads" device you describe between the controller and motor (sounds like a circuit breaker) be redundant if the controller can do the same thing? ??
Dan Pfeiffer
?
On 2021-05-27 1:56 pm, Dave Yamakuchi via groups.io wrote:
?
NEC generally calls for 175% of Full Load Ampere rating for dual element time delay fuses for motors.? Fast acting fuses, inverse time or instantaneous breakers are all rated differently for the short circuit protection.
?
However, this only covers short circuit protection, and not an overload condition. Thermal or electronic 'overloads' located after the control circuit directly before the wires to the motor is the generally accepted practice for protecting against an overloaded motor. Fishing line or seaweed maybe binding the shaft and preventing it from spinning freely, for instance.? Or prop stuck in the mud.? This is in addition to the fuses.? Depending on the motor's service factor and temperature rise specs, the overloads usually shut off at no more than 115% or 125% of the FLA.
?
Overloads have a much tighter current limit range, but they're somewhat slower acting to allow for inrush at startup. (fuses and breakers often vary widely in the actual trip current)? They're meant to recreate the motor's windings' temperature to trip the control circuit.? Also, they're resettable.
?
See Article 430 of the NEC for more info.
?
On Thursday, May 27, 2021, 12:39:03 PM CDT, Dan Pfeiffer < dan@...> wrote: ?
?
For those running 48V 8-20kW systems, what are you doing for fuse protection on your battery bank?? Brands and sizes??? My 12kW motor has a constant capacity of 250 amps.? The peak capacity is 600.? I don't know what I might actually see for short duration peaks but I was thinking a 300 amp fuse might blow in normal operating if I had a momentary peak on the motor draw.?? What are others using??
Dan Pfeiffer
?
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Dan, your Sevcon will normally try its best to make the motor turn as it's commanded so it could indeed cause an overload of the discharge C-rating and potentially damage the cells. I wouldn't try to protect them with a fuse because it could fail right when you need it. Consider increasing the available C-rating (big cells, paralleled cells or higher C-rated cells). Alternatively (but more complex) would be an active current monitor (shunt + microcontroller) that would monitor battery current and (first) sound an alarm and then (second) disconnect the contactor before damage could occur. This approach would allow an emergency override so the you could sacrifice your batteries to save the boat if the situation demanded it. I'm following this approach in my build using ESP32-based microcontrollers.
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I was not concerned with protecting the battery, I was concerned with protecting the wiring and not causing a fire in the case of a short in the large battery wiring while at the same time allowing for the occasional current spikes that might occur in normal operation.??? Are those current spikes limited by the controller programming??
Your micro controller system sounds intriguing.? It seems like an extension of the controller.? Will the Sevcon try it's best up to some per-programmed limit? Say the 600 amp max capacity of the motor?? Is that something the Sevcon is capable of being programmed for?? Acceleration curves can be programmed into the controller.? Is that the controller not responding as demanded by the throttle input?? If you slam the throttle the controller will ramp up at the programmed acceleration rate, not necessarily as fast as you commanded it to.?? But if the load on the motor changes is that a different scenario.?? Do acceleration curves still apply??
Will your emergency override also potentially sacrifice the controller to overload?? And then your in the same position as if you had lost the battery??? How much would the primary wiring be oversized to keep it from being the weak link in an emergency override??? Do monitors like the Vicrtron have programmable settings for high current alarms??
Dan Pfeiffer
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Show quoted text
On 2021-05-28 7:24 am, Randy Cain wrote:
Dan, your Sevcon will normally try its best to make the motor turn as it's commanded so it could indeed cause an overload of the discharge C-rating and potentially damage the cells. I wouldn't try to protect them with a fuse because it could fail right when you need it. Consider increasing the available C-rating (big cells, paralleled cells or higher C-rated cells). Alternatively (but more complex) would be an active current monitor (shunt + microcontroller) that would monitor battery current and (first) sound an alarm and then (second) disconnect the contactor before damage could occur. This approach would allow an emergency override so the you could sacrifice your batteries to save the boat if the situation demanded it. I'm following this approach in my build using ESP32-based microcontrollers.
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If they have "thermal overload protection," then yes, that's probably the protection, in addition to the fuses, that you want.? The overload 'setting' (electronic ols are 'set', thermal elements are fixed/chosen) needs to correspond to your motor's FLA (x1.15 or x1.25 _max_, depending on sf & temp).
IDK the sevcon, but IIRC, this was a decent intro to basic motor starters.? I'm guessing your device is probably more a vfd than a simple contactor, but you still want the ocp and overloads.
https://youtu.be/aml0VGzNXEo
On Thu, May 27, 2021 at 3:43 PM, Dan Pfeiffer <dan@...> wrote:
Very useful info.? Thanks.?
Does a controller (like the Sevcon4) handle current limiting to the motor??? It does have thermal overload control which is related.? Would the "overleads" device you describe between the controller and motor (sounds like a circuit breaker) be redundant if the controller can do the same thing? ??
Dan Pfeiffer
?
On 2021-05-27 1:56 pm, Dave Yamakuchi via groups.io wrote:
?
NEC generally calls for 175% of Full Load Ampere rating for dual element time delay fuses for motors.? Fast acting fuses, inverse time or instantaneous breakers are all rated differently for the short circuit protection.
?
However, this only covers short circuit protection, and not an overload condition. Thermal or electronic 'overloads' located after the control circuit directly before the wires to the motor is the generally accepted practice for protecting against an overloaded motor. Fishing line or seaweed maybe binding the shaft and preventing it from spinning freely, for instance.? Or prop stuck in the mud.? This is in addition to the fuses.? Depending on the motor's service factor and temperature rise specs, the overloads usually shut off at no more than 115% or 125% of the FLA.
?
Overloads have a much tighter current limit range, but they're somewhat slower acting to allow for inrush at startup. (fuses and breakers often vary widely in the actual trip current)? They're meant to recreate the motor's windings' temperature to trip the control circuit.? Also, they're resettable.
?
See Article 430 of the NEC for more info.
?
On Thursday, May 27, 2021, 12:39:03 PM CDT, Dan Pfeiffer <dan@...> wrote:
?
?
For those running 48V 8-20kW systems, what are you doing for fuse protection on your battery bank?? Brands and sizes??? My 12kW motor has a constant capacity of 250 amps.? The peak capacity is 600.? I don't know what I might actually see for short duration peaks but I was thinking a 300 amp fuse might blow in normal operating if I had a momentary peak on the motor draw.?? What are others using??
Dan Pfeiffer
?
|
I use a class T-fuse at the battery, the primary criterion was
ability to safely and effectively interrupt a potentially massive
short circuit from the LiFePo bank.? There's a notional rating for
fuse capacity (trip current) which you've referenced, but there's
another rating which is the absolutely maximum that the fuse can
safely and effectively interrupt.? This rating is tied to the
physical design and construction of the fuse/CB.?
If a short circuit exceeds this interrupting capacity, the
current could arc over the device and/or other catastrophic
failure modes.? Please note that the interrupting capacity
drastically changes on whether the current is AC or DC, so check
that on the datasheet.? AC can self extinguish on polarity
reversal, this can't happen with DC.
This is largely an issue for Lithium chemistries, I don't believe
that (most?) LA batteries are physically capable of generating the
very intense short circuit currents which is necessary to overcome
the interrupting capacity.
Kai
On 28/5/21 7:00 am, john via groups.io
wrote:
toggle quoted message
Show quoted text
It would still be really nice
to have a breaker right at the battery to protect in the event
of a short somewhere along the line.
Looks like Amazon has 48V
breakers up to 300A.? I saw a fuse for 500A or 600A, but
they're only rated to 32V.??
John
On Thursday, May 27, 2021, 03:43:31 PM CDT, Dan Pfeiffer
<dan@...> wrote:
Very useful info.? Thanks.?
Does a controller (like the Sevcon4) handle current
limiting to the motor??? It does have thermal overload
control which is related.? Would the "overleads"
device you describe between the controller and motor
(sounds like a circuit breaker) be redundant if the
controller can do the same thing? ??
Dan Pfeiffer
?
On
2021-05-27 1:56 pm, Dave Yamakuchi via groups.io
wrote:
?
NEC generally calls for 175% of
Full Load Ampere rating for dual element time
delay fuses for motors.? Fast acting fuses,
inverse time or instantaneous breakers are all
rated differently for the short circuit
protection.
?
However, this only covers short
circuit protection, and not an overload
condition. Thermal or electronic 'overloads'
located after the control circuit directly
before the wires to the motor is the generally
accepted practice for protecting against an
overloaded motor. Fishing line or seaweed
maybe binding the shaft and preventing it from
spinning freely, for instance.? Or prop stuck
in the mud.? This is in addition to the
fuses.? Depending on the motor's service
factor and temperature rise specs, the
overloads usually shut off at no more than
115% or 125% of the FLA.
?
Overloads have a much tighter
current limit range, but they're somewhat
slower acting to allow for inrush at startup.
(fuses and breakers often vary widely in the
actual trip current)? They're meant to
recreate the motor's windings' temperature to
trip the control circuit.? Also, they're
resettable.
?
See Article 430 of the NEC for
more info.
?
On Thursday, May 27, 2021, 12:39:03 PM
CDT, Dan Pfeiffer <dan@...>
wrote: ?
?
For those running 48V 8-20kW systems,
what are you doing for fuse protection
on your battery bank?? Brands and
sizes??? My 12kW motor has a constant
capacity of 250 amps.? The peak capacity
is 600.? I don't know what I might
actually see for short duration peaks
but I was thinking a 300 amp fuse might
blow in normal operating if I had a
momentary peak on the motor draw.?? What
are others using??
Dan Pfeiffer
?
|
I use a class T-fuse at the battery, the primary criterion was ability to safely and effectively interrupt a potentially massive short circuit from the LiFePo bank.? There's a notional rating for fuse capacity (trip current) which you've referenced, but there's another rating which is the absolutely maximum that the fuse can safely and effectively interrupt.? This rating is tied to the physical design and construction of the fuse/CB.?
If a short circuit exceeds this interrupting capacity, the current could arc over the device and/or other catastrophic failure modes.? Please note that the interrupting capacity drastically changes on whether the current is AC or DC, so check that on the datasheet.? AC can self extinguish on polarity reversal, this can't happen with DC.
This is largely an issue for Lithium chemistries, I don't believe that (most?) LA batteries are physically capable of generating the very intense short circuit currents which is necessary to overcome the interrupting capacity.
?
Kai
|
The SEVCON GEN4 controller can limit the battery current and in any case limits the motor current.
?
You can take a look at the fuse integrated in the controller:
- 48V size 2 - 275A max motor - 250A fuse (x 48V = 12 kW)
- 48V size 4 - 450A max motor - Fuse 425A (x 48V = 20 kW)
- 48V size 6 - 650A max motor - 750A fuse (x 48V = 36 kW)
?
An additional fuse on the battery bank protects against short circuits in the wiring.
Thierry LEQUEU
|
Breakers come instantaneous or inverse time and the % of fla you should choose is based on which.
On Thu, May 27, 2021 at 4:06 PM, john via groups.io <oak_box@...> wrote:
It would still be really nice to have a breaker right at the battery to protect in the event of a short somewhere along the line.
Looks like Amazon has 48V breakers up to 300A.? I saw a fuse for 500A or 600A, but they're only rated to 32V.??
John
On Thursday, May 27, 2021, 03:43:31 PM CDT, Dan Pfeiffer <dan@...> wrote:
Very useful info.? Thanks.?
Does a controller (like the Sevcon4) handle current limiting to the motor??? It does have thermal overload control which is related.? Would the "overleads" device you describe between the controller and motor (sounds like a circuit breaker) be redundant if the controller can do the same thing? ??
Dan Pfeiffer
?
On 2021-05-27 1:56 pm, Dave Yamakuchi via groups.io wrote:
?
NEC generally calls for 175% of Full Load Ampere rating for dual element time delay fuses for motors.? Fast acting fuses, inverse time or instantaneous breakers are all rated differently for the short circuit protection.
?
However, this only covers short circuit protection, and not an overload condition. Thermal or electronic 'overloads' located after the control circuit directly before the wires to the motor is the generally accepted practice for protecting against an overloaded motor. Fishing line or seaweed maybe binding the shaft and preventing it from spinning freely, for instance.? Or prop stuck in the mud.? This is in addition to the fuses.? Depending on the motor's service factor and temperature rise specs, the overloads usually shut off at no more than 115% or 125% of the FLA.
?
Overloads have a much tighter current limit range, but they're somewhat slower acting to allow for inrush at startup. (fuses and breakers often vary widely in the actual trip current)? They're meant to recreate the motor's windings' temperature to trip the control circuit.? Also, they're resettable.
?
See Article 430 of the NEC for more info.
?
On Thursday, May 27, 2021, 12:39:03 PM CDT, Dan Pfeiffer <dan@...> wrote:
?
?
For those running 48V 8-20kW systems, what are you doing for fuse protection on your battery bank?? Brands and sizes??? My 12kW motor has a constant capacity of 250 amps.? The peak capacity is 600.? I don't know what I might actually see for short duration peaks but I was thinking a 300 amp fuse might blow in normal operating if I had a momentary peak on the motor draw.?? What are others using??
Dan Pfeiffer
?
|
Good idea.? Should have thought of that.? The controller has a 500A fuse.? So if I match that at the battery I will protect the wiring and have enough capacity to match what the controller should max out at.?
I have found these options so far (thanks for suggestions...)
Here's all the Blue Seas options
EV West
Battle Born (a little weak on listing specs)
Fasttronix
Selections from Amazon - Not necessarily marine rated...
Still looking for more...
Dan Pfeiffer
?
toggle quoted message
Show quoted text
On 2021-05-28 1:58 am, Thierry wrote:
The SEVCON GEN4 controller can limit the battery current and in any case limits the motor current.
?
You can take a look at the fuse integrated in the controller:
- 48V size 2 - 275A max motor - 250A fuse (x 48V = 12 kW)
- 48V size 4 - 450A max motor - Fuse 425A (x 48V = 20 kW)
- 48V size 6 - 650A max motor - 750A fuse (x 48V = 36 kW)
?
An additional fuse on the battery bank protects against short circuits in the wiring.
Thierry LEQUEU
|
The basic rule is to size the conductors to meet the load, then size the overcurrent disconnect to protect the wiring. I thought you were concerned about drawing too many amps from your batteries :-) Yes, as others are suggesting, an overcurrent disconnect should be placed inline between the battery and the Sevcon. It should be rated at about 125% of the ampacity of that conductor. You can apparently program a maximum current limit with the Sevcon ... I don't have Sevcon programming skills yet but I may need to get there. Sudden current increases occur when the controller is set to maintain a particular rpm in the presence of a sudden increase in rotational resistance like a crab pot. Also, my concern is that both house and propulsion power is supplied by the same bus so the Sevcon can only protect and limit propulsion current.
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I don't think the controller is at risk because it's the current sink, not source. Its fuse is there in case an overload occurs so that the controller might be saved from damage (like a motor winding short). My Sevcon Gen4 Size 6 controllers should never have to reach their maximum current (500A) as I'm running at the top of their voltage range (max 118vdc, 96vdc nominal).
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In any case, when your setups are done, perform a max stress test of the system at berth, or on the water, in good conditions.
Just to be safe.
Good luck ! Please post any experiences.
Carsten
On Sunday, 30 May 2021, 02:26:12 GMT+8, Randy Cain <randylcain@...> wrote:
I don't think the controller is at risk because it's the current sink, not source. Its fuse is there in case an overload occurs so that the controller might be saved from damage (like a motor winding short). My Sevcon Gen4 Size 6 controllers should never have to reach their maximum current (500A) as I'm running at the top of their voltage range (max 118vdc, 96vdc nominal).
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On 28/5/21 2:56 pm, Kai wrote:
This is largely an issue for Lithium chemistries, I don't believe that (most?) LA batteries are physically capable of generating the very intense short circuit currents which is necessary to overcome the interrupting capacity.
A Lead Acid battery bank can source some pretty fearsome fault currents too. Just less likely to have the battery back burst into flames and start and unstoppable fire, but overheated wiring is not friendly. I have a 250amp fuse bolted directly to the positive battery terminal. My motor is rated at 110amps short term and I set the controller current limit at 60. The fuse will only ever blow if a wire comes adrift and shorts or the switching transistors in the controller have a catastrophic short failure. And I suspect the transistor casing would blow and extinguish the arc before the fuse blew anyway. Even ignoring the battery, the wires to the battery could start a decent fire on their own if there was short circuit current from my lead-acid pack for any length of time. In my city several months ago, a route bus caught on fire in service. No injuries, every one baled out in good time, but the vehicle is a write off. The fire started when the 'jump start' wiring to the jump start socket shorted against some part of the body. There was no fuse at the battery end on the jump start wiring between the battery and the socket on the outside of the vehicle, so it's presumed the battery just dumped all it's power into the wiring and something caught fire.
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Randy Cain
Matthew Geier