Electrical power components are power switching devices. They control the flow of electricity to physical devices like Motors, Heaters, etc in power circuits. In the US, electrical power circuits must follow the National Electric Code (NEC). The NEC requires every power circuit to include a disconnecting means and circuit overload protection. The disconnecting means can be a switch, but it’s often a Circuit Breaker or Fuse because they also provide circuit overload protection. In a motor power circuit, the NEC also requires motor overload protection.
Circuit overload protection prevents the wires from overheating and starting a fire. Motor overload protection prevents the motor from overheating and starting a fire.
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What is a Circuit Breaker ?
A circuit breaker is a manually operated electrical power switch that can detect short circuit and overload conditions. It turns itself Off when one of these conditions is detected. Short circuit conditions are detected magnetically and overload conditions are detected thermally.
The advantage of using a circuit breaker for circuit protection, compared to a fused disconnect ? A circuit breaker doesn’t destroy itself breaking the circuit, so you can just turn it back On.
What is a Fused Disconnect ?
A Fused Disconnect is the combination of a manual operated electrical power switch and a fuse. A fuse is a thin metal wire in a sand packed paper wrapper. It breaks the flow of electrical power a when short circuit or overload causes the metal wire to literally burn up. A fuse breaks the flow of electrical power by graceful self destruction.
The disadvantage of using a fused disconnect for circuit protection, compared to a circuit breaker ? A fuse destroys itself breaking the circuit, so you can’t turn it back on after it operates, you have to replace the fuse.
What is a Motor Starter ?
A Motor Starter is a device or combination of devices used to power and control a motor. At a minimum, a motor starter includes the following power safety devices. In addition, a Motor Starter generally includes a device (Contactor, Soft Start, Variable Frequency Drive, etc.) to control the motor.
- A Disconnecting Means, a method of manually disconnecting motor power to allow the motor to be serviced.
- Short Circuit Protection, a method of automatically disconnecting motor power (to prevent a fire) if a short circuit condition is detected.
- Motor Overload Protection, a method of disconnecting motor power (to prevent damage to motor driven equipment) if a motor overload condition is detected.
What is an FVNR Starter ?
A Full Voltage Non Reversing (FVNR) Starter is a 3 Phase motor controller with one motor contactor. An Across the Line (ATL) Starter means the same thing as an FVNR Starter. The contactor opens and closes the power circuit to turn the motor on and off.
- Full Voltage means the contactor simply opens and closes the motor power circuit.
- Non Reversing means the motor can’t be reversed using one 3 Phase motor contactor.
What is an FVR Starter ?
A Full Voltage Reversing (FVR) Starter a 3 Phase motor controller with two motor contactors. Instead of simply opening and closing the power circuit to turn the motor on and off, it uses a forward and reversing contactor to control motor direction.
- Full Voltage means the contactors simply open and close the motor power circuit.
- Reversing means the motor can be reversed by using the forward and reverse motor contactors to change (swap) the connection of any two of three power conductors.
- The direction of a 3 Phase Motor is controlled by reversing (swapping) the connection of any two of three power conductors.
What is a Soft Starter ?
A Soft Starter is a 3 Phase motor controller with a simple solid state power controller. Instead of simply opening and closing the power circuit like a motor contactor, it ramps the motor voltage up or down to turn the motor on and off more smoothly to eliminate electrical surges and mechanical shock.
A Soft Starter is more expensive than a motor contactor, but provides the added benefit of reducing electrical and mechanical shocks associated with starting and stopping a motor.
What is a Variable Frequency Drive (VFD) ?
A Variable Frequency Drive (VFD) is a 3 Phase motor controller with an advanced solid state power controller. Instead of simply ramping the motor voltage up or down like a soft start to turn the motor on and off, a Variable Frequency Drive (VFD) allows motor speed to be controlled at all times while running.
A Variable Frequency Drive (VFD) is more expensive than a Soft Start (SS), but provides the added benefit of controlling motor speed.