A motor controller is a device or device type coordinating in an electric motor's act, which may have a manual/automatic means to start/stop a motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and electrical faults. Motor controllers may use electromechanical switching, or may use power electronics devices to control a motor's speed and direction.
Fig. 1
[5], [6] A motor starter is an electrical device that safely starts/stops/protects an electric motor, acting as a basic switch, controlling the motor's power flow, with protection mechanisms like overload relays to prevent damage from high inrush currents or overheating.
It's often made of a contactor and overload (Fig. 1).
[8] a closed Allen Bradly [1.3] magnetic motor starter
[8] an Allen Bradly magnetic motor starter
[9] the motor starter's closer view inside
They can be be small and akin to house light switches, or larger dedicated switches of high amperage circuits control can maybe either single pole (one line) or double/triple pole devices (switch 2/3 lines). If a double/triple pole manual motor starter is turned off, the power from the power cable is completely disconnected from the motor. Manual starters may also have matched heaters, overload protectors to open in case of overcurrent, being properly sized to a motor they protect or they either open too soon or won't protect the motor. Manual motor controls's downside is they can't have remotely located on/off controls.
Labels
Some single pole starters must only be for 120 V motors.
L1 (Line 1) must be the "hot" black wire. T1 is Motor 1 out and goes from the starter to the motor. In this case, Neutral "White" is carried through to the motor bypassing the starter altogether. This wiring should not be used on 240 volt circuits.
240 V, 1 phase motors must use a 2 pole starter. L1 (Line 1) must connect a "hot" wire. L2 (Line 2) must connect the other "hot" wire. T1 and T2 are corresponding motor out connections and must carry through to the motor.
Three Phase motors require 3 pole starters and each of the "hot" lines must be switched through the starter.
They always have 2 functions:
There's a way to stop/start the motor.
There is overload protection.
[5] Connector numbers vary among manufacturers.
A single phase connections' 2 current-carrying wires are "hot" and "neutral". In North American, the 240 V service are both hot wires but we stick with the hot/neutral naming to keep it simple.
L1 (1): first line in from power source (phase 1 for 3ph / Neutral for 1ph)
L2 (3): second line in from power source (phase 2 for 3ph / Hot for 1ph* see below for alternate wiring using L2 & L3)
L3 (5): third line in from power source (phase 3 for 3ph / NC for for 1ph)
T1 (2): 1st line out to motor (phase 1 for 3ph / Neutral for 1ph)
T2 (4): 2ndd line out to motor (phase 2 for 3ph / Hot for 1ph* see below for alternate wiring)
T3 (6): 3rd line out to motor (phase 3 for 3ph / NC for 1ph)
"-||-" (1-2, 13-14, 53-54)is a normally Open NO contact (closes when the relay energizes)
"-|/|-" (95-96) is a normally closed NC contact (opens when the thermal overloads trip if associated with the overload block - as shown in all three diagrams)
"-|/|-" is a normally closed NC contact (opens when the relay energizes if associated with the relay coil as auxiliary circuit - as shown in the motor reversing diagram as coil isolation contacts)
M: Relay Coil
[9] the motor starter's closer view inside
[6] A motor starter is drawn as this:
Manual motor starter A manual switch trips open an overload and uses an overload heater sized to the motor FLA, limited to manual control. single pole is suitable for 120 V uses
Usual manual motor starters:
A 2-pole manual motor starter has:
1 overload heater
suitable for single phase 240 or 208 V operation
Does this device fully disconnect the motor?
A 2-pole manual motor starter has:
often used on 3 phase 208 V motors
3 overloads needed
limited to manual control
A 3 Phase Manual Motor Starter or nail push button (old school)
“M” contacts
“M” contacts control the motor.
The other devices protect the motor from overloads.
L1, L2 and L3 label incoming power or “line” terminals.
The usual color coding is red, black, blue
M contacts
Power to the motor is controlled by 3 “M” contacts.
Numbers and letter combinations distinguish motors and their associated starters
Overload heaters
Current to the motor flow through the overload “heaters”.
Heat produced is proportional to the current's square.
T1, T2, T3
3 phase motor terminals are labelled “T1”, “T2” and “T3” in North America.
The IEC standard uses “U”, “V”, & “W”.
Motor
The motor (O/L) is controlled by a push button.
Overload operation
The overload contact is mechanically operated by overload heaters.
The motor runs normally. Note the motor currents.
Phase A is now drawing well over rated current--It's an issue.
The overload contact opens.
The M coil is de-energised.
The motor stops
Notes: See that the overload heaters don’t open.
They cause the overload contact to open.
Overload heaters are sized to match the motor full load current.
Alloy = a combination of 2+ metals, or a metal with a nonmetal, creating a solid solution, compound, or mixture, mixtures made by melting various components and cool down, creating a solid material. Alloys are useful due to have enhanced properties unlike pure metals (e.g. increased strength, hardness, or corrosion resistance).
Smaller control wires run through contacts.
Motor current runs through the heater.
Heat produced is proportional to the square of current.
Excess current produces enough heat to melt the solder.
When the control circuit opens the M contacts open and current to the motor ceases.
Relays are selected so that the heater matches the FLA of the motor
Which thermal units would you use if a motor had an FLA of 84 A?
CC 103
CEC books needed
The reset button can be used to push the O/L contact back to a closed position once the solder has frozen
Overload protection alternatives are bi-metal relay or as part of a variable speed drive or with sensors and a microprocessor based control system.
Fig 2.
Traditional power circuit (Fig. 3)
This is from the 21st century. M contacts are replaced by transistors and transistors controlled by a micro processor Current to the motor is monitored by the VFD (Fig. 2).
Fig 3.
Motor data and motor current are used to determine if the motor is overloaded
No-voltage protection (NVP) is a safety system, for big and small installations with a need for early warning of condensation or pipe bursts, showing success in homes and offices. It's used in the building trade to monitor attics and roof voids in order to keep roof leak damage to a minimum. It is also fitted in HVAC installations to monitor condensation in cooled ceilings as well as pipe bursts.
Any devices in yellow stops the motor.
No-voltage protection (NVP) is a broader group of protection disconnecting power if voltage is too low/lost, but may or may not need manual reset.
E.g. 1#
Fig. A basic NVP circuit
Multiple stops:
How can we connect multiple starts?
Like this:
(28-506 of the 2024 CEC; Pg 245) A grounded control circuit (GCC) is a type of control circuit with 1 side of its control voltage (often negative/neutral side) connected to ground for safety.
If a control circuit of a motor controller's power is received conductively from a grounded system, it's arranged for an accidental ground in the wiring from the controller to any remote or signal device won't
(a) start the motor; or
(b) stop the motor from stopping by the normal operation of any control or safety device in the control circuit.
This overload contact's position won’t work, but technically still like in older usages.
What occurs if the overload opens?
The overload contact shortens:
Placing an overload after the coil is still common. But the overload after the coil meets CEC rules if the device is in the same enclosure. It is not “remote”.
Any remote and/or signaldevice outside a controller must connect to the coil's ungrounded side.
Jogging/Inching is to start a motor briefly, only running as the jog button works.
Only engage the motor by holding the button.
Note: A disavantage is precise motor movement and what it controls.
The motor runs as the N/O push button works.
Jogging with a selector switch
A selector switch can be jogged/runned, as you put a selector in switch in line as we close it in line it becomes a t, if opened it breaks the contact becomes unsable
In “RUN” position, the N/O button works as a start button.
In “JOG” position, it works as a jog button.
Jogging via jog button
This circuit has stop, start and jog, with some issues.
If this motor runs, as it’s normally closed, as it breaks down the jog, it pushes the contact open. If it affects the job button, basically killing the circuit.
This circuit can “lock in” from a jog.
This circuit can’t be used if it's a hazard.
A jogging motor/Inching motor is a motor activated in short bursts for precise movement or positioning, not continuous operation-- giving it a little nudge, not full power.
This circuit uses a control relay. It’s an energized coil with contacts--why it says CR, as a controlled relay.
Does the start button work?
No, because it jogs it off.
The start button won't work as it jogs it off.
Does the jog button work?
Can it lock in?
Many control circuits have a hand-off-auto switch (HOA) or selector switch.
The switch facilitates testing and inspection of motors, as we can use them as jogs often.
This is a basic control circuit for a motor controlled by a float switch.
A Hand-Off-Auto switch is often included.
A basic control circuit for a motor controlled by a float switch with a hand-off-auto switch often included.
"ON" hand-off-auto In the hand position the motor runs no matter the float switch's position.
Is this be an issue?
"OFF" hand-off-auto In the hand position the motor runs regardless of the position of the float switch.
Could this be a problem?
"AUTO" hand-off-auto “Auto” is the HOA switch's usual position.
The motor only starts if the float switch is closed.
E.g. 1# In the Auto position the pump keeps the liquid in the tank at a pre-set level.
The tank level cycles between the level where the pump starts and shuts off.
Overtime liquid level
Many automatic controls works this way.
They don’t keep a set value.
They keep a quantity between 2 values.
Combination Motor Starter (1)
Often we add overcurrent protection and a disconnecting means in the same enclosure as the motor starter.
This is called a combination motor starter.
In this case, a fused disconnect provides a disconnecting means and overcurrent protection.
A circuit breaker can give overcurrent protection and a disconnecting means.
Combination starters needs less space and work to install.
A typical combination starter has these features:
fused disconnect
motor starter with thermal overloads
through cover reset
controls on cover
Green objects are fuses
NEMA Type 1, CR307, CR308: Size 6 Floor-Mounted:
NEMA Full Voltage Power Devices
NEMA Rated Full Voltage Starters - Magnetic
Section 1
CR307, CR308, CR387 Magnetic Starters
Nonreversing, Combination, NEMA Type 1, 3R, 12, 4/4X
400 Horsepower Maximum
NEMA Sizes 5-6
600 Volts Maximum 50/60 Hertz
Outlines, Dimensions in. (mm)
NEMA starter sizes:
Each light post draws 12 A at 120 V.
Each light post requires a separate circuit.
We must be able to switch the lights on.
old Algonquin College map
Solution 1
Feed a bank of switches from the panel near the fixtures.
Feed the fixtures from the switches.
Security must be able to control the lights from C Block.
Designs often have constraints added, sometimes very late.
This causes these issues:
Line loss
Cost (copper is costly)
Maintenance (bigger system, more costly to control)
Routing
Can a relay help?
This is a 3 poles switch controlled by a coil
[4] What can this hardware look like?
Manufacturer drawing:
This is a big contactor.
Note terminals & current rating.
Advantages:
Only 2 wires back to security
Very small load on the wires to security
Small conduit
Small wire
Small cost
Can add more fixtures to panel
What about the clock connected to the panel?
A better way is:
Hardware for better solutions
How much current a coil needs:
Not much – note the units.
Not the difference between “inrush” and “sealed.”
[1] Wikipedia
[1.1] Dangerous restart
[1.2] Magnetic starter
[1.3] Allen-Bradley
[1.4]
[1.5]
[1.6]
[2] Contactor vs. Motor Starter: Core Differences - Bay Power
[6] Magnetic Motor Starters as Controllers | A comparison of NEMA- and IEC-type devices - IAEI Magazine
[7] https://kjcontracting.net/products/allen-bradley-509-bod-nema-size-1-fvnr-starter