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Thread: Questions about proper accessory components for a 60V system

              
   
   
  1. #1
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    Questions about proper accessory components for a 60V system

    Howdy,

    I have purchased a 60V 2,000W Boma brushless motor & speed controller to use on a go kart. (~$ 250.00 for both)
    https://www.ebay.com/itm/163360846900

    I have worked with 12V, 24V, 36V & 48V but, 60V is new to me.

    What type of switches & fuses or circuit breakers are recommended or necessary for use in a 60V system?

    I have used (12V) automotive fuses many times without problems, but 60V seems to be "pushing it".

    I have also used marine style circuit breakers, but they are usually rated @ 48V max.

    The current specs. on this 60V controller says, 35A.

    What is the Rule of thumb or guidelines on the proper & safe use of fuses & circuit breakers? ...tips? ...or suggestions?
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    Senior Member Ted Dillard's Avatar
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    There's only one rule of thumb, really. Use components that are rated for 60VDC, or more. You cannot guess that a switch rated at whatever VAC will work for what you want it to, with DC current.

    Travis can explain better than I can why you need a switch (or anything else) rated for DC. There's no cross-reference for AC rated switches. Basically, my stab at an explain is that DC is going all one direction, all the time. AC reverses, so there's a point at which it's at 0, so that will quench an arc. DC won't. (How'mI doin, Travvy? )

    There are no shortcuts, or workarounds, or cheap solutions that are even remotely safe. The EV suppliers generally have high DC voltage stuff, but it costs.
    Last edited by Ted Dillard; 09 November 2018 at 1717.
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    Empulse R #24 frodus's Avatar
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    Quote Originally Posted by Ted Dillard View Post
    There's only one rule of thumb, really. Use components that are rated for 60VDC, or more. You cannot guess that a switch rated at whatever VAC will work for what you want it to, with DC current.

    Travis can explain better than I can why you need a switch (or anything else) rated for DC. There's no cross-reference for AC rated switches. Basically, my stab at an explain is that DC is going all one direction, all the time. AC reverses, so there's a point at which it's at 0, so that will quench an arc. DC won't. (How'mI doin, Travvy? )

    There are no shortcuts, or workarounds, or cheap solutions that are even remotely safe. The EV suppliers generally have high DC voltage stuff, but it costs.
    Pretty good Ted! You learnded! hehe

    Basically, yeah, DC and AC ratings aren't the same. It specifically needs to say it can handle 60VDC or higher in order to use that safely. Another thing, is that the fuses, or switches, have minimum gaps, so when they "break" the circuit, there's enough distance at those higher voltages to stop an arc.

    The Controller and batteries are DC, so you need to find fuses that can withstand 60VDC.

    I wouldn't use circuit breakers, just use a fuse, rated for the proper current. Also, I don't think I'd use both a fuse and breaker. Use one or the other, but it's overkill for both at 60V. If you're not sure, post here and I can take a peak. Looks like you need to do 35A continuous, but at 40A, what do you want to do? Break in 5 seconds? 10 seconds? Fuses have a curve (so do circuit breakers).

    ANN and CNN style fuses (used on Sevcon and Curtis) are good ones to use. I go to allfuses.com and get fuses, they're pretty cheap. I have some coming from there now, and they're 350A DC rated fuses.
    Travis

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    Thanks guys,
    ...doing some research & gathering info.

    Thanks for the Allfuses.com suggestion, they seem to have lots of stuff.

    Any particular reason you don't recommend using circuit breakers?

    They seem to be a good "dual purpose" solution, (not for breaking the "arc" in emergencies, that's what the electronic contactor is for, right?)
    but, as a main cut-off switch (for maintenance & storage) & a (resettable) fuse.

    What about something like this?
    https://www.ebay.com/itm/NEW-AIRPAX-...bF13:rk:4:pf:0

    What about simple switches? ...like for the on/off circuit, It's 60V but, only like 1A.

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    Here is some info I found & wanted to share

    Fuse
    A fuse is an automatic means of removing power from a faulty system; often abbreviated to ADS (Automatic Disconnection of Supply). Circuit breakers can be used as an alternative to fuses, but have significantly different characteristics.

    Speed
    The speed at which a fuse blows depends on how much current flows through it and the material of which the fuse is made. The operating time is not a fixed interval, but decreases as the current increases. Fuses have different characteristics of operating time compared to current. A standard fuse may require twice its rated current to open in one second, a fast-blow fuse may require twice its rated current to blow in 0.1 seconds, and a slow-blow fuse may require twice its rated current for tens of seconds to blow.
    Fuse selection depends on the load's characteristics. Semiconductor devices may use a fast or ultrafast fuse as semiconductor devices heat rapidly when excess current flows. The fastest blowing fuses are designed for the most sensitive electrical equipment, where even a short exposure to an overload current could be very damaging. Normal fast-blow fuses are the most general purpose fuses. A time-delay fuse (also known as an anti-surge or slow-blow fuse) is designed to allow a current which is above the rated value of the fuse to flow for a short period of time without the fuse blowing. These types of fuse are used on equipment such as motors, which can draw larger than normal currents for up to several seconds while coming up to speed.

    Breaking Capacity
    The breaking capacity is the maximum current that can safely be interrupted by the fuse. This should be higher than the prospective short-circuit current. Miniature fuses may have an interrupting rating only 10 times their rated current. Some fuses are designated High Rupture Capacity (HRC) and are usually filled with sand or a similar material. Fuses for small, low-voltage, usually residential, wiring systems are commonly rated, in North American practice, to interrupt 10,000 amperes. Fuses for commercial or industrial power systems must have higher interrupting ratings, with some low-voltage current-limiting high interrupting fuses rated for 300,000 amperes. Fuses for high-voltage equipment, up to 115,000 volts, are rated by the total apparent power (megavolt-amperes, MVA) of the fault level on the circuit.

    Rated Voltage
    The voltage rating of the fuse must be equal to or, greater than, what would become the open-circuit voltage. For example, a glass tube fuse rated at 32 volts would not reliably interrupt current from a voltage source of 120 or 230V. If a 32V fuse attempts to interrupt the 120 or 230 V source, an arc may result. Plasma inside the glass tube may continue to conduct current until the current diminishes to the point where the plasma becomes a non-conducting gas. Rated voltage should be higher than the maximum voltage source it would have to disconnect. Connecting fuses in series does not increase the rated voltage of the combination, nor of any one fuse.
    Medium-voltage fuses rated for a few thousand volts are never used on low voltage circuits, because of their cost and because they cannot properly clear the circuit when operating at very low voltages

    Voltage Drop
    The manufacturer may specify the voltage drop across the fuse at rated current. There is a direct relationship between a fuse's cold resistance and its voltage drop value. Once current is applied, resistance and voltage drop of a fuse will constantly grow with the rise of its operating temperature until the fuse finally reaches thermal equilibrium. The voltage drop should be taken into account, particularly when using a fuse in low-voltage applications.
    Source: https://en.wikipedia.org/wiki/Fuse_(electrical)

    Circuit Breaker
    A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.
    Circuit breakers are made in varying sizes, from small devices that protect low-current circuits or individual household appliance, up to large switchgear designed to protect high voltage circuits feeding an entire city. The generic function of a circuit breaker, RCD or a fuse, as an automatic means of removing power from a faulty system is often abbreviated as OCPD (Over Current Protection Device).
    Source: https://en.wikipedia.org/wiki/Circuit_breaker

    Extra-low voltage (ELV) is an electricity supply voltage in a range which carries a low risk of dangerous electrical shock.[1][2][3][4] There are various standards that define extra-low voltage. The International Electrotechnical Commission member organizations and the UK IET (BS 7671:2008) define an ELV device or circuit as one in which the electrical potential between conductor or electrical conductor and earth (ground) does not exceed 50 V a.c. or 120 V d.c. (ripple free). EU's Low Voltage Directive applies from 50 V a.c. or 75 V d.c.
    The IEC and IET go on to define actual types of extra-low voltage systems, for example SELV, PELV, FELV. These can be supplied using sources including motor / fossil fuel generator sets, transformers, switched PSU's or rechargeable battery. SELV, PELV, FELV, are distinguished by various safety properties, supply characteristics and design voltages.
    Some types of landscape lighting use SELV / PELV (extra-low voltage) systems. Modern battery operated hand tools fall in the SELV category. In more arduous conditions 25 volts RMS alternating current / 60 volts (ripple-free) direct current can be specified to further reduce hazard. Lower voltage can apply in wet or conductive conditions where there is even greater potential for electric shock. These systems should still fall under the SELV / PELV (ELV) safety specifications

    In the European Union, the Low Voltage Directive defines low voltage starting from 50 V AC, and 75 V DC. The directive only covers electrical equipment and not voltages appearing inside equipment or voltages in electrical components. IEC 60364 defines it as 50 V AC and 120 V DC.
    Source: https://en.wikipedia.org/wiki/Extra-low_voltage

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    Empulse R #24 frodus's Avatar
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    Quote Originally Posted by Functional Artist View Post
    Thanks guys,
    ...doing some research & gathering info.

    Thanks for the Allfuses.com suggestion, they seem to have lots of stuff.

    Any particular reason you don't recommend using circuit breakers?

    They seem to be a good "dual purpose" solution, (not for breaking the "arc" in emergencies, that's what the electronic contactor is for, right?)
    but, as a main cut-off switch (for maintenance & storage) & a (resettable) fuse.

    What about something like this?
    https://www.ebay.com/itm/NEW-AIRPAX-...bF13:rk:4:pf:0

    What about simple switches? ...like for the on/off circuit, It's 60V but, only like 1A.
    Circuit breakers shouldn't be used as a means of disconnect. They're not rated to turn things on and off. They're meant to break a circuit, and reset if needed. You can use them, but they're more expensive per amp than a suitable fuse. You should size it so it never breaks except for in an emergency.

    If you want a cutoff, use a cutoff switch, or some anderson connectors you can unplug.


    Even for simple switches, use something rated for 60V. Most are rated for 12V. I wouldn't use them, as they could become welded. If you can't find one that is 60V, then use 12V, through a relay that has rated contacts for 60V or higher.
    Travis

  7. #7
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    Quote Originally Posted by frodus View Post
    Circuit breakers shouldn't be used as a means of disconnect. They're not rated to turn things on and off. They're meant to break a circuit, and reset if needed. You can use them, but they're more expensive per amp than a suitable fuse. You should size it so it never breaks except for in an emergency.

    If you want a cutoff, use a cutoff switch, or some anderson connectors you can unplug.


    Even for simple switches, use something rated for 60V. Most are rated for 12V. I wouldn't use them, as they could become welded. If you can't find one that is 60V, then use 12V, through a relay that has rated contacts for 60V or higher.
    Thank you, very helpful info.

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    Doing more research, I asked different demographics this same question.

    The electronics folks mentioned:
    "All components used must be rated to at least the max. expected currents and/or voltages.
    A good design leaves a safety margin on top of that, e.g. >= 10 %."

    So, this means for a 60VDC (nominal) system the full SLA battery voltage would be ~66.5VDC. (13.3V top charge voltage x 5 batteries = 66.5VDC)
    ...plus ~10% safety margin would put us in the 72VDC range.

    Then, my buddy PStechPaul on DIYelectriccars found these for me:
    "Here is a line of fuses designed for battery operated vehicles up to 80V, and current ratings 35-500 amps. Interrupting ratings are given for 48V and are 6 times the current rating. They are about $7 each in all current ratings."

    https://www.mouser.com/datasheet/2/2...80v-523197.pdf

    https://www.mouser.com/Circuit-Prote...ng%7c0&FS=True

    For simple switches, I found these 72VDC 16A DPST (double pole single throw) switches (basically (2) switches in (1) unit) for ~$10.00 ea.
    It can be used to turn the speed controller on/off & also an indicator light or dash (meter etc.) at the same time. (dual purpose)

    https://www.mouser.com/ProductDetail...oDaAHPRVpI8%3d

  9. #9
    Empulse R #24 frodus's Avatar
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    Quote Originally Posted by Functional Artist View Post
    Doing more research, I asked different demographics this same question.

    The electronics folks mentioned:
    "All components used must be rated to at least the max. expected currents and/or voltages.
    A good design leaves a safety margin on top of that, e.g. >= 10 %."

    So, this means for a 60VDC (nominal) system the full SLA battery voltage would be ~66.5VDC. (13.3V top charge voltage x 5 batteries = 66.5VDC)
    ...plus ~10% safety margin would put us in the 72VDC range.

    Then, my buddy PStechPaul on DIYelectriccars found these for me:
    "Here is a line of fuses designed for battery operated vehicles up to 80V, and current ratings 35-500 amps. Interrupting ratings are given for 48V and are 6 times the current rating. They are about $7 each in all current ratings."

    https://www.mouser.com/datasheet/2/2...80v-523197.pdf

    https://www.mouser.com/Circuit-Prote...ng%7c0&FS=True

    For simple switches, I found these 72VDC 16A DPST (double pole single throw) switches (basically (2) switches in (1) unit) for ~$10.00 ea.
    It can be used to turn the speed controller on/off & also an indicator light or dash (meter etc.) at the same time. (dual purpose)

    https://www.mouser.com/ProductDetail...oDaAHPRVpI8%3d
    Yeah, that fuse is essentially the CNN or ANN style fuse I was talking about.

    ANN:
    https://www.allfuses.com/all-product...anufacturer=29

    CNN:
    https://www.allfuses.com/all-product...anufacturer=31

    That switch is good for 16A. Don't use it to put pack voltage to the controller. That needs a larger switch. That switch might be good for the enable signal (if the controller even has that). DO NOT use it on the B+ wires to the controller, that 16A fuse won't take it for long. Needs to be rated for your 35A rating of the controller.
    Travis

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    Quote Originally Posted by frodus View Post
    Yeah, that fuse is essentially the CNN or ANN style fuse I was talking about.

    ANN:
    https://www.allfuses.com/all-product...anufacturer=29

    CNN:
    https://www.allfuses.com/all-product...anufacturer=31

    That switch is good for 16A. Don't use it to put pack voltage to the controller. That needs a larger switch. That switch might be good for the enable signal (if the controller even has that). DO NOT use it on the B+ wires to the controller, that 16A fuse won't take it for long. Needs to be rated for your 35A rating of the controller.
    The 80VDC 16A switch will be only be used to turn the speed controller on & off. (probably like, 60V & ~150mA)

    We will not be running the "full current" (60VDC & ~35A) that's going to the motor" thru it. (Sorry, I guess I wasn't clear enough)

    It looks like I will also need a couple of other 60VDC compatible switches.

    We need an on/off/on switch to operate the (3) speed function, maybe like this: (~$13.00)
    https://www.mouser.com/ProductDetail...5s4NxymdJW4%3d

    ...& also an off/on (momentary) switch to operate the reverse function , maybe like this: (~$35.00)
    https://www.mouser.com/ProductDetail...5a18puLSzRI%3d


    *Could you explain the difference between an ANN fuse & A CNN fuse?...the specs don't seem to be much different.
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