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Electric Motors
Changing Voltage
Electrical Terms
Voltage = (Volts) = Pressure to push electrons in a circuit.
Amperage = (Amperes) = Measurement of electrons flowing
in a circuit.
Resistance = (Ohms) = Resistance to the flow of electrons in
a circuit.
Electric Motors
Changing Voltage
Ohm’s Law
In a circuit, when volts, amps, and/or ohms are changed, the values
for the others will change, accordingly.
E=IxR
E = Volts
I = Amperes
R = Ohms
I = E
R
E
R=E
I
I
R
Electric Motors
Changing Voltage
Ohm’s Law
E = Volts
I = Amperes
R = Ohms
E
I xR
To use the chart to the right, cover up what you are
trying to solve for.
Example: A 240V motor has an amperage draw of
6 amps. How many ohms are in the circuit?
Electric Motors
Changing Voltage
Ohm’s Law
E = Volts
I = Amperes
R = Ohms
To use the chart to the right, cover up what you are
trying to solve for.
Example: A 240V motor has an amperage draw of
6 amps. How many ohms are in the circuit?
Solution: Cover the “R” on the chart and then perform
the math.
E
I xR
R=E
I
Electric Motors
Changing Voltage
Ohm’s Law
E = Volts
I = Amperes
R = Ohms
To use the chart to the right, cover up what you are
trying to solve for.
Example: A 240V motor has an amperage draw of
6 amps. How many ohms are in the circuit?
Solution: Cover the “R” on the chart and then perform
the math.
240
6 xR
R=E
I
= 40 ohms
Electric Motors
Changing Voltage
Ohm’s Law
E = Volts
I = Amperes
R = Ohms
E
I xR
To use the chart to the right, cover up what you are
trying to solve for.
Example: We change that 240V motor to run on 120V.
The amperage draw has changed as
it is now a series circuit as opposed to a
parallel due to differences in resistance in the
circuit. Calculate the resistance of
the motor now that it is hooked up to
low voltage.
Electric Motors
Changing Voltage
Ohm’s Law
E = Volts
I = Amperes
R = Ohms
E
I xR
To use the chart to the right, cover up what you are
trying to solve for.
Example: We change that 240V motor to run on 120V.
The amperage draw has changed as
it is now a series circuit as opposed to a
parallel due to differences in resistance in the
circuit. Calculate the resistance of
the motor now that it is hooked up to
low voltage.
Solution: Cover the “R” on the chart and then perform
the math.
R=E
I
Electric Motors
Changing Voltage
Ohm’s Law
E = Volts
I = Amperes
R = Ohms
120
12 x R
To use the chart to the right, cover up what you are
trying to solve for.
Example: We change that 240V motor to run on 120V.
The amperage draw has changed to 12 amps as
it is now a series circuit as opposed to a
parallel due to differences in resistance in the
circuit. Calculate the resistance of
the motor now that it is hooked up to
low voltage.
= 10 ohms
Solution: Cover the “R” on the chart and then perform
the math.
R=E
I
Electric Motors
Changing Voltage
Series -vs- Parallel
In a series circuit, all electrons flow in one common pathway
Series notes:
If one component fails, they all fail.
It takes higher pressure (voltage) to make electrons to their work.
Running windings on high voltage motors are wired in series.
Electric Motors
Changing Voltage
Series -vs- Parallel
In a parallel circuit, electrons flow in multiple pathways.
Parallel notes:
If one component fails, the others will continue to work.
It takes lower pressure (voltage) to make more electrons do equal work.
Running windings on low voltage motors are wired in parallel.
Electric Motors
Changing Voltage
Dual Voltage Motor Wired For 120 Volts
Running Windings
Wired in Parallel
Electric Motors
Changing Voltage
Dual Voltage Motor Wired For 240 Volts
Running Windings
Wired in Series