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Old 02-05-2018, 03:34   #1
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Electric motor wiring

Good morning,

I'm wiring a 48 v 3 phase brushless DC motor. The round trip is 20 to 30 ft (approx). The continuous load is 50 amp and max load is 100 amp. I purchased 4 gauge awg tinned wire. I am fusing at the battery post at 100 amps. Am I alright at this gauge? I will be restricting the amperage to the motor to 80 amps maximum. The wires will be bundled but not enclosed.

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Old 02-05-2018, 04:17   #2
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Re: Electric motor wiring

Before we get to the wire have you managed to locate a DC motor that operates with sinusoid power in differing time domains?

Is this a windlass motor? Does it have three lugs?
Is one of the lugs ground?

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Old 02-05-2018, 04:39   #3
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Re: Electric motor wiring

In addition, what code applies here? Is this a boat and you need to meet ABYC or your US based home/business where NEC might apply? Is this a continuous service or intermittent? What voltage drop does the application allow? What is the ambient temperature range? Do you need low smoke cable per insurance or code requirements?

Personally, I would not use AWG-4 copper for an 80A circuit. But it might be ok depending on several other factors that are unkniwn.
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Old 02-05-2018, 05:29   #4
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Re: Electric motor wiring

#4 AWG wire is good for about 5,000 Ft- Amps (3% VD) at 48 V, so about 166Amps over a 30 ft. (round trip) run (but only rated for 136A @ 105C).

See ➥
And ➥

Chart only goes to 32V (nominal)
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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Old 09-05-2018, 05:48   #5
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Re: Electric motor wiring

Can we assume the motor controller is at the motor so only need two cables from the battery? Are they inside a engine compartment? I always size up a bit. I would have 2awg (105*) outside the engine, fused at 200A. But 4awg is just in range if you are sure you will not exceed 80A. There are many others, but I like this wire chart; Voltage Drop Calculator
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electric, electric motor, motor, wiring

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